JP7516673B2 - Drive system and method for rail vehicles - Google Patents

Description

The present invention relates to a drive system and drive method for railway vehicles using storage batteries.

Railway lines include electrified sections where railway vehicles can receive power from overhead lines, and non-electrified sections where there are no overhead lines and no power supply.
A battery train is a railway vehicle that is equipped with a rechargeable battery system that serves as an energy source for propulsion. In electrified sections, the train receives power from overhead lines and uses this power to propel the train while charging the battery system. In non-electrified sections, the train runs using the battery as an energy source.

A storage battery system is generally configured by connecting multiple storage battery modules in series and parallel, and charges and discharges with a DC voltage. When charging, the charging equipment needs to apply an appropriate DC voltage to control the charging speed and target value. Similarly, when the storage battery system discharges, the power consumption equipment such as the drive inverter that uses the energy also has an appropriate DC voltage range, and deviation from this range may result in failure to perform the intended operation, a decrease in efficiency, or the occurrence of a malfunction.
Here, Patent Document 1 discloses an in-vehicle power storage device that charges a battery unit made up of a plurality of batteries that can be switched between series and parallel connection from an external DC power source or from an external AC power source via a power converter.
Furthermore, Patent Document 2 discloses a technology for switching the circuit configuration of the storage batteries in an electricity storage device mounted on an electric vehicle between a series connection and a parallel connection, thereby enabling easy and efficient charging in a single charging operation from a low-voltage power source, without incurring costs or effort and without using a step-up/step-down chopper or the like.

In addition, it is known that DC/DC converters that convert a DC voltage into a different DC voltage generally have different circuits when stepping up and stepping down, and DC/DC converters that have both step-up and step-down functions have both circuit structures internally.

JP 2019-004604 A JP 2006-067683 A

When considering a battery train that is operated in a manner that charges in electrified sections where DC power is supplied from overhead lines and discharges in non-electrified sections, it is desirable for the battery system to be charged to a voltage slightly higher than the rated voltage of the overhead lines. This is because, while power consuming devices are in a voltage range that operates with the overhead line voltage, the voltage of a battery storage system generally drops as the charging rate decreases, and this ensures that the power consuming devices can continue to operate even when the charging rate decreases.

In general, overhead line voltage, whether DC or AC, fluctuates greatly both upwards and downwards depending on the operational balance between multiple powered vehicles and regenerative vehicles connected to the overhead line. Therefore, to control the charging voltage of the battery system, a DC/DC converter capable of both stepping up and stepping down the voltage (hereinafter referred to as a "step-up/step-down DC/DC converter") is required. This step-up/step-down DC/DC converter has both a step-up circuit and a step-down circuit, so it is more expensive and has a larger weight and volume than a step-up-only or step-down-only DC/DC converter.

In order to solve the above problems, one representative drive system for railway vehicles of the present invention comprises a first power supply unit consisting of a storage battery system and a DC-DC power converter mounted on the railway vehicle, and a DC power supply drive system that is driven by DC power supplied by the first power supply unit or DC power supplied from a second power supply unit having a configuration different from the first power supply unit and supplies a predetermined power to a load device mounted on the railway vehicle, the storage battery system having a plurality of storage battery units and a series-parallel switching means for switching the connection state between the plurality of storage battery units to a series state or a parallel state, and the series-parallel switching means switches the series-parallel state between the plurality of storage battery units between a case where the first power supply unit supplies DC power and a case where DC power is supplied from the second power supply unit.

According to the present invention, since charging control to the battery system is possible using only a step-down converter or a step-up converter, it is possible to realize a smaller converter section and lower costs compared to using a step-up/step-down converter.When charging in an electrified section, voltage transformation is performed via only a step-down converter or a step-up converter, and when charging/discharging in a non-electrified section, voltage transformation is not required, so that it is possible to improve energy conversion efficiency compared to using a step-up/step-down converter.
Problems, configurations and effects other than those described above will become apparent from the description of the following embodiments.

1 is a diagram showing a system configuration of a railway vehicle drive system according to a first embodiment of the present invention; 1 is a diagram showing an example of the configuration of a storage battery system having N storage battery units. FIG. 1 illustrates an example of a configuration of a step-down DC/DC converter. 1 is a diagram showing a functional configuration of a control device for a railcar drive system according to a first embodiment; FIG. 2 is a diagram showing an interlocking circuit of a series contactor and a parallel contactor according to the first embodiment. FIG. 2 is a diagram showing a control table of the railcar drive system according to the first embodiment. 1 is a circuit diagram of a railway vehicle drive system according to a first embodiment in an electrified section. FIG. 1 is a circuit diagram of a railway vehicle traction system according to a first embodiment in a non-electrified section. FIG. 1 is a diagram showing, in tabular form, a sequence when switching a circuit state from an electrified section to a non-electrified section of a railway vehicle traction system according to a first embodiment. FIG. 1 is a diagram showing, in tabular form, a sequence when switching a circuit state from a non-electrified section to an electrified section of a railway vehicle traction system according to a first embodiment. FIG. FIG. 1 is a diagram showing the simplest voltage equivalent circuit of a storage battery system. FIG. 11 is a diagram showing a voltage relationship for illustrating the effect of the first embodiment. 1 is a diagram showing a configuration in which a DC electric railcar drive system is replaced with an AC electric railcar drive system in a drive system for a railway vehicle according to a first embodiment. FIG. 2 is a diagram showing a configuration in which a direct current electric railcar drive system is replaced with an electric diesel railcar drive system in the drive system for a railway vehicle according to the first embodiment. 1 is a diagram illustrating a circuit configuration of a bidirectional step-down DC/DC converter according to a first embodiment. FIG. 11 is a diagram showing a system configuration of a boost charging type railway vehicle drive system according to a second embodiment. FIG. 11 is a diagram showing a control table of a drive system for a boost charging type railway vehicle according to the second embodiment. FIG. 11 is a circuit diagram of a boost charging type railway vehicle drive system in an electrified section according to a second embodiment. FIG. 11 is a circuit diagram of a boost charging type railway vehicle drive system in a non-electrified section according to a second embodiment. FIG. 11 is a diagram showing a voltage relationship for illustrating the effect of the second embodiment. FIG. 11 is a diagram showing a comparison of the current and voltage of the storage battery systems in the first and second embodiments. FIG. 1 is a diagram showing a cross current when power supplies are connected in parallel. 13A to 13C are diagrams illustrating storage battery units in different internal states according to a third embodiment. FIG. 13 is a graph showing OCV-integrated current-SOC for parallel switching control in a low voltage charging configuration in the third embodiment. FIG. 11 is a diagram illustrating a functional configuration of a control device according to a third embodiment. FIG. 13 is a diagram showing a storage battery system having a cross current suppression circuit according to a fourth embodiment. FIG. 13 is a diagram showing, in tabular form, a sequence for switching the circuit state from an electrified section to a non-electrified section of a railway vehicle traction system according to a fourth embodiment. FIG. 13 is a diagram showing, in tabular form, a sequence for switching the circuit state from a non-electrified section to an electrified section in a railway vehicle traction system according to a fourth embodiment. FIG. 13 is a diagram showing the configuration of a series-connected, midpoint-grounded storage battery system according to a fifth embodiment. FIG. 1 is a diagram showing the configuration of a permanently midpoint grounded battery system. FIG. 1 is a diagram showing a circuit state of a permanently center-grounded battery system when the batteries are connected in series (at high voltage). FIG. 1 is a diagram showing a circuit state of a permanently center-grounded battery system when it is connected in parallel (at low voltage).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First to fourth embodiments of a railway vehicle drive system according to the present invention will be described below with reference to the drawings.
In the following embodiments, the battery constituting the power storage device is a lithium-ion battery, but is not limited to a lithium-ion battery, and may be a lead battery, nickel-metal hydride battery, or other power storage device.
It should be noted that the present invention is not limited to these embodiments. In addition, in the drawings, the same parts are denoted by the same reference numerals.

1 is a diagram showing a system configuration of a railway vehicle traction system according to a first embodiment of the present invention. In the figure, solid lines indicate power transmission paths, and dotted lines with arrows indicate transmission paths of information such as control signals and sensor values.
The railway vehicle drive system 100 is intended for DC battery-powered electric trains that use DC power from overhead lines in electrified sections and power from storage batteries in non-electrified sections, and is composed of a DC electric train drive system 110, a non-electrified section compatible system 120, a control device 130, and a driver's cab 140, and in electrified sections, it receives DC power from a DC overhead line 111.

First, the DC electric train drive system 110 is a conventional drive system for DC electric trains that run on electrified sections of DC overhead lines, and is specifically configured to include a pantograph (Pan) 112 that connects or opens the P side of the train drive system 100 to the DC overhead line 111, an overhead line high-speed circuit breaker (HB) 113 that opens the train drive system 100 at high speed in the event of an abnormality while running on overhead line power, a main circuit contactor (LB) 114 that controls the open/closed state of the train drive system 100 under normal conditions, a reactor (FL) 115 that suppresses sudden current changes such as surges, and a drive circuit breaker (RC) 116 that receives DC power and drives the train. The drive system 100 for a railway vehicle has an inverter (INV) 116 that outputs three-phase AC power to drive a motor 118 for a railway vehicle, a static inverter (SIV) 117 that receives DC power and outputs AC and DC power for the auxiliary devices, an auxiliary device 117a (auxiliary device 1) that is driven by AC 440V power, an auxiliary device 117b (auxiliary device 2) that is driven by AC 100V power, an auxiliary device 117c (auxiliary device 3) that is driven by DC 100V power, an induction motor M118 that receives the three-phase AC power from the inverter 116 and outputs motive power during powering and outputs regenerative power during regeneration, and a ground point 119 (which is often grounded to the tracks via the wheels) that grounds the N side of the drive system 100 for a railway vehicle.

Next, the non-electrified section compatible system 120 is a system that is connected to the DC electric train drive system 110 so that the railway vehicle drive system 100 can run on non-electrified sections, and has a storage battery system 121 that charges and discharges power from the storage battery, a step-down DC/DC converter 122 that reduces the DC overhead line power and supplies it to the storage battery system 121, and a battery high-speed circuit breaker (BTHB) 124 that quickly opens the storage battery system 121 in the event of an abnormality.

Here, the overhead line high-speed circuit breaker 113 and the storage battery high-speed circuit breaker 124 are in a conductive state when the railway vehicle drive system 100 is started up and in an open state when the system is shut down, and are always in a conductive state during system startup except when an abnormality occurs.

The control device 130 is a device that controls the drive system 100 for railway vehicles, and based on information input from the DC electric train drive system 110, the non-electrified section compatible system 120, and the cab 140, controls each device of the DC electric train drive system 110 and the non-electrified section compatible system 120, and outputs necessary information to the cab 140.

The cab 140 is an interface with the driver, receiving information from the railway vehicle drive system 100 and displaying it to the driver, while also transmitting the driver's operations to the control device 130.

The storage battery system 121 is a storage battery system that can change the system voltage by opening and closing the contactor, and has storage battery units 121a and 121b, a series contactor 121c, and parallel contactors 121d and 121e.

The storage battery units 121a and 121b each have at least one storage battery cell, which is connected in series and parallel. In general, the storage battery units of large storage battery systems such as railway systems have multiple cells electrically connected in series and parallel, and output terminals for connecting to the outside, and the storage batteries are contained in units called storage battery modules that incorporate a controller board called a cell controller.

Here, the voltage and charge capacity of the battery unit are determined by the number of cells connected in series and in parallel. Increasing the number of cells connected in series inside the battery unit increases the voltage of the battery unit, and increasing the number of cells connected in parallel increases the charge capacity of the battery unit.

The series contactor 121c and the parallel contactors 121d and 121e are electromagnetic contactors similar to the main circuit contactor 114 and the battery system contactor 123, and generally, by electromagnetically moving opposing two-pole plates to open and close the contact state, it is possible to remotely operate the circuit to be conductive (on state) or open (off state).

The positive and negative poles of the storage battery units 121a and 121b are connected to each other via parallel contactors 121d and 121e, respectively. On the other hand, the positive and negative poles of the storage battery units 121a and 121b are connected to each other via a series contactor 121c, with the unit with the series contactor 121c connected to the negative pole side being placed on the high voltage side, and the unit with the series contactor 121c connected to the positive pole side being placed on the low voltage side.

In the battery storage system 121, when the series contactor 121c is on and the parallel contactors 121d and 121e are off, the two battery units 121a and 121b are in a series state, and when the series contactor 121c is off and the parallel contactors 121d and 121e are on, the two battery units 121a and 121b are in a parallel state. If the internal configurations of the battery units 121a and 121b are the same, the voltage in the series connection state is twice that of the parallel connection state.

When connected in parallel, each storage battery unit has the same voltage, but when connected in series, the same current flows but the voltages do not spontaneously become the same. If a voltage difference exists between the units when connected in series and then they are connected in parallel, cross currents will occur, so it is desirable for the units to be at the same potential even when connected in series. Also, if the internal series-parallel cell arrangements within each storage battery unit are the same, and the battery deterioration rates, etc. are the same, then ideally the voltage between each storage battery unit will be the same even when switching between series and parallel.

The number of units in the storage battery system 121 and the series-parallel configuration thereof are not limited to the two storage battery units connected as 2 series-1 parallel or 1 series-2 parallel as shown in Fig. 1. Fig. 2 is a diagram showing an example of the configuration of a storage battery system having N storage battery units.
For the number of units N (BT1 to BTN) in the storage battery system 121 shown in Figure 2, when there are two divisors n1 and n2, including 1, such that N = n1 x n2, it is generally possible to have a connection state of n1 in series, n2 in parallel, or n2 in series, n1 in parallel, and the voltage and capacity of the storage battery system 121 can be flexibly switched.

The step-down DC/DC converter 122 is a device that steps down and outputs an input direct current voltage. FIG. 3 is a diagram showing an example of the configuration of the step-down DC/DC converter 122.
The step-down DC/DC converter 122 shown in Fig. 3 is composed of a switch element (SW1) 122a such as an FET, a diode (D1) 122b, a coil (FL1) 122c, and a capacitor (C1) 122d. The capacitor (C1) 122d is an element for flattening the ripple voltage, and is not necessarily required depending on the nature of the load. Note that the step-down DC/DC converter 122 does not have to be of the configuration shown in Fig. 2, and may be any device that generally converts voltage.

The step-down DC/DC converter 122 has external connection terminals P, N, and PLow, and smoothes the pulse voltage generated by the switching of the switch element (SW1) 122a with an LC filter, and steps down the DC voltage between P and N between PLow and N and outputs it.
3 operates only in the direction of inputting a current at the P terminal and outputting a current at the PLow terminal, but the step-down DC/DC converter 122 of the first embodiment is sufficient for only charging the storage battery system 121. When the output of the DC/DC converter 122 is to be set to 0, the switch element (SW1) 122a is set to a non-conducting state.

DC/DC converters use the switching action of switch elements to convert voltage, so they are generally more efficient than linear regulators, which use a resistor to drop the voltage. For this reason, they are used particularly in applications that consume large amounts of power, such as railway vehicles.

In addition, since the minimum configuration of a step-down DC/DC converter and a step-up DC/DC converter are generally different, a DC/DC converter capable of both step-down and step-up must have both circuits, making it larger and more expensive than a DC/DC converter that is only step-up or step-down configured.

The battery system contactor (BPK) 123 controls the conductive (on) or open (off) state of the DC train drive system 110 in response to the DC voltage of the battery system 121.

In electrified sections, the overhead line voltage is not applied directly to the battery system 121, and instead the voltage is applied via the step-down DC/DC converter 122, so the battery system contactor 123 is kept open.

In non-electrified sections, the DC voltage of the battery system 121 is applied directly to the DC electric train traction system 110, so the battery system contactor 123 is in a conductive state. At this time, the step-down DC/DC converter 122 opens the switch element 122a and is in an open state.

The battery high-speed circuit breaker 124 is a contactor for quickly disconnecting the battery system 121 from other circuits in an emergency.

Fig. 4 is a diagram showing a functional configuration of the control device 130 of the railcar traction system 100 according to the embodiment 1. The functional configuration shown in Fig. 4 is a configuration for control according to the present invention, and generally has other functions as well.
The control device 130 is composed of a storage battery status management unit 131, a vehicle control logic unit 132, and a main circuit switching control unit 133. The functions of the control device 130 include obtaining various operation commands and status information of various devices of the railroad vehicle drive system 100 from the cab 140 or a vehicle monitoring device (not shown), controlling the various devices of the railroad vehicle drive system 100, and transmitting cab display information to the cab 140 to be recognized by the driver.

The battery status management unit 131 monitors the status of the battery system, performs status calculations, inputs information such as battery voltage, battery current, and battery temperature, and outputs the charging rate, allowable current, and battery usability determination of the battery system 121. The battery voltage, battery current, battery temperature, etc. may be measured values of sensors in the battery module and transmitted from the cell controller, or these sensors may be attached externally to the battery module.

Here, the charging rate is an index that indicates how much charge the battery currently has remaining compared to the charge capacity when the battery is fully charged. This charging rate is calculated from the integral value of the current flowing through the battery and the voltage of the battery when it is not energized, called the open circuit voltage.

The allowable power is the predicted value of the power that the battery can charge and discharge, and is generally the predicted value of the charging power at which the upper limit voltage of the battery is reached or the discharge power at which the lower limit voltage of the battery is reached. This allowable power can be predicted as the cell power at the upper or lower limit voltage after predicting the open circuit voltage from the battery's charging rate and the battery resistance from the charging rate and temperature.

The battery usability determination unit is a unit that determines whether the battery can be charged or discharged. If the battery is higher than a high threshold or lower than a low threshold based on temperature, charging rate, and voltage, this determination stops the use (charging and discharging) of the battery from the perspective of safety and preventing deterioration.

Generally, the above charging rate, allowable power, and battery usability determination can be calculated in smaller units rather than the entire battery system, which can improve control accuracy and safety. In each embodiment of the present invention, the calculation target is not limited to the entire system or to the cell unit.

The vehicle control logic unit 132 calculates and controls the output of inverters and converters related to vehicle drive in the control device 130, detects abnormal conditions, and controls circuit interruption by the high-speed circuit breaker. Specifically, the vehicle control logic unit 132 receives the driving command, auxiliary use command, and emergency stop command obtained from the cab 140, the charging rate, allowable power, and battery usability determination obtained from the battery status management unit 131, and the pantograph status, contactor status, and vehicle status obtained from each device itself or a measuring device not shown, and outputs a high-speed circuit breaker opening and closing signal that opens and closes the overhead line high-speed circuit breaker 113 and the battery high-speed circuit breaker 124, a step-down DC/DC converter output command value that controls the output of the step-down DC/DC converter 122, an inverter output command value that controls the output of the inverter 116, a static inverter output command value that controls the output of the static inverter 117, and cab display information for the cab 140.

Here, vehicle status refers to general status information necessary for vehicle control, such as vehicle speed, position, passenger weight, rainfall/snowfall conditions, air temperature, interior temperature, and door open/close status, but is not limited to these information.

Regarding the output of the step-down DC/DC converter 122, the output of the inverter 116 and the output of the static inverter 117, the power consumption of various devices is predicted based on driving commands such as the vehicle's driving speed and acceleration/deceleration, and auxiliary device usage commands, and their output command values are calculated and operated.

The output command value of the step-down DC/DC converter 122, the output command value of the inverter 116, and the output command value of the static inverter 117 are generally square wave PWM signals when the switching elements of each power converter are transistors. This PWM signal outputs a gate voltage for opening or closing the transistor by a gate drive device (not shown) built into each power converter.

Cab display information refers to information that the driver should check and display, such as abnormality flags for various devices, pantograph status, and battery charge rate. However, it is not limited to this information.

As for the high-speed circuit breaker opening/closing signal, when an emergency stop command is input from the cab 140 or when the vehicle control logic unit 132 judges the state of various equipment and detects an abnormality that requires circuit interruption, a disconnection signal is output for the overhead line high-speed circuit breaker 113 and the storage battery high-speed circuit breaker 124. The overhead line high-speed circuit breaker 113 and the storage battery high-speed circuit breaker 124 are normally in a conductive state.

The main circuit switching control unit 133 controls the pantograph and contactor of the main circuit, and controls switching of the conduction path of the main circuit. Specifically, the main circuit switching control unit 133 receives the contactor opening/closing command, pantograph up/down command, pantograph state, and contactor state obtained from the cab 140, and outputs a pantograph up/down signal for moving the pantograph 112 up and down, and a contactor opening/closing signal for opening and closing the various contactors 114, 123, 121c, 121d, and 121e, respectively.

5 is a diagram showing an interlocking circuit of the series contactor 121c and the parallel contactors 121d and 121e according to the first embodiment. In the first embodiment, if the series contactor 121c and any of the parallel contactors 121d and 121e are simultaneously in a conductive state, the storage battery unit is short-circuited and a large current flows, which is dangerous. Therefore, it is desirable that the control device 130 has a software safety structure that performs sequence control while monitoring the contactor state so that the series contactor 121c and any of the parallel contactors 121d and 121e are not simultaneously in a conductive state, and also has a hardware safety structure that takes precedence over the software safety structure.

As shown in FIG. 5, a contactor generally has a contact that is linked to the main circuit operation of the contactor and a coil that generates a magnetic field during contact operation to operate the open/close state of other contactors. The contactor control b contact 121c1 of the series contactor 121c is a b contact that opens and closes in reverse with the series contactor 121c when current is applied. When the series contactor 121c is in a conductive state, the b contact 121c1 is in an open state and the contactor control coil 121c2 does not generate a magnetic field. At this time, the parallel contactors 121d and 121e are in an open state regardless of the signal from the control device 130. When the series contactor 121c is in an open state, the b contact 121c1 is in a conductive state and the contactor control coil 121c2 generates a magnetic field. At this time, the parallel contactors 121d and 121e can be in a conductive state if the signal from the control device 130 is a conduction command. Similarly, when at least one of the parallel contactors 121d and 121e is in a conductive state, the series contactor 121c is in an open state regardless of a signal from the control device 130, and when both the parallel contactors 121d and 121e are in an open state, the series contactor 121c can be in a conductive state if the signal from the control device 130 is a conductive command. In other words, the conductive state and open state of the series contactor 121c and the parallel contactors 121d and 121e are mutually exclusive.

FIG. 6 is a diagram showing a control table of the railcar traction system 100 according to the first embodiment.
For each condition, control operations are performed to operate the pantograph, contactor, converter and inverter. The charge/discharge state of the battery is passively determined by these operations. The overall control conditions are determined by the electrified/non-electrified section, the chargeable state and the operating state.

First, the operation of the pantograph and contactor is determined by whether the section is electrified or non-electrified, and in electrified sections, the circuit configuration is switched to one that receives overhead power, and in non-electrified sections, the circuit configuration is switched to one that allows the train to run on power from the battery storage system 121. The switching may be performed by the driver via the cab 140, or may be performed automatically by the control device 130.

Next, the operation of the converter and inverter is determined by the chargeable state and the operating state. The chargeable state indicates whether the battery is fully charged or not. In the fully charged state, further charging is avoided, and in the not fully charged state, charging continues below the allowable power until the battery is fully charged. The operating state refers to the operating state of the induction motor 118 of the railway vehicle, and is classified into a powering state in which the vehicle increases its speed by the output torque of the induction motor 118, a coasting or stopped state in which the vehicle is neither accelerated nor decelerated by the induction motor 118, and a regenerative state in which the vehicle decelerates while generating electricity with the induction motor 118.

Figure 7 is a circuit diagram 100a in an electrified section of a railway vehicle drive system 100 according to Example 1. In an electrified section (conditions No. 1 to 6 shown in Figure 6), the circuit state is the same as that of circuit diagram 100a shown in Figure 7. In the figure, solid lines indicate conductive parts of the circuit, and dotted lines indicate open parts of the circuit.

In an electrified section, the train drive system 100 supplies DC power from the overhead line 111 to the inverter 116 and the static inverter 117, and also steps down the power in the step-down DC/DC converter 122 to charge the storage battery system 121, whose voltage has been reduced in the parallel state. The pantograph 112 is raised (on) to receive power from the overhead line. The main circuit contactor 114 is on the necessary path and is in a conductive (on) state. The storage battery system contactor 123 is in an open (off) state because if it were conductive, the overhead line voltage would be applied directly to the storage battery system 121, making it impossible to control the charging rate and the charging voltage. In order to make the storage battery system 121 have a lower voltage than the overhead line 111, the series contactor 121C is in an open (off) state, and the parallel contactors 121d and 121e are in a conductive (on) state.

In electrified section conditions No. 1 to 6 shown in Figure 6, the chargeable state and operating state are different, and the converter/inverter operation and the battery charge/discharge operation are different. The static inverter 117 is always operating in conditions No. 1 to 6. In conditions No. 1 to 6, all power consumed by the vehicle is supplied from the overhead line 111 or from regenerative power, and the battery system 121 is charging or stopped.

No. 1 is a case where the section is electrified, the battery is not fully charged, and the operating state is powered. At this time, the train drive system 100 powers the induction motor 118 with overhead line power and charges the storage battery system 121 in parallel via the step-down DC/DC converter 122. Therefore, the inverter 116 is turned on to supply three-phase AC power that powers the induction motor 118, and the step-down DC/DC converter 122 is turned on to output DC charging power to the battery.

No. 2 is the case where the train is in an electrified section, the battery is fully charged, and the train is in a powered operating state. At this time, the train drive system 100 powers the induction motor 118 with overhead line power, and the battery system 121 does not charge or discharge. Therefore, the inverter 116 is turned on to supply three-phase AC power that powers the induction motor 118, and the step-down DC/DC converter 122 is turned off.

No. 3 is a case where the train is in an electrified section, the battery is not fully charged, and the train is coasting or stopped. At this time, the Railroad Rolling Stock Agency's traction system 100 does not operate the induction motor 118 and charges the battery system 121. Therefore, the inverter 116 is turned off and the step-down DC/DC converter 122 is turned on to output DC charging power to the battery.

No. 4 is a case where the train is in an electrified section, the battery is fully charged, and the train is coasting or stopped. At this time, the train drive system 100 does not operate the induction motor 118, and the battery system 121 does not charge or discharge. Therefore, the inverter 116 is turned off, and the step-down DC/DC converter 122 is turned off.

No. 5 is a case where the train is in an electrified section, the battery is not fully charged, and the operating state is regeneration. At this time, the train drive system 100 operates the induction motor 118 in a regenerative manner and charges the battery system 121 in a parallel state. Therefore, the inverter 116 is turned on, obtains regenerative three-phase AC power from the induction motor 118 and converts it to DC power, and the step-down DC/DC converter 122 is turned on to output DC charging power to the battery.

No. 6 is the case where the train is in an electrified section, the battery is fully charged, and the operating state is regenerative. At this time, the train drive system 100 operates the induction motor 118 in a regenerative manner, and the storage battery system 121 does not charge or discharge. Therefore, the inverter 116 is turned on, regenerative three-phase AC power is obtained from the induction motor 118 and converted to DC power, and the step-down DC/DC converter 122 is turned off. The regenerative power is consumed by the static inverter 117 and is also sent to the overhead line 111.

Figure 8 is a circuit diagram 100b in a non-electrified section of the railway vehicle drive system 100 of Example 1. In a non-electrified section (conditions No. 7 to 12 shown in Figure 5), the circuit state is the same as that of circuit diagram 100b shown in Figure 8. In the figure, solid lines indicate conductive parts of the circuit, and dotted lines indicate open parts of the circuit.

In non-electrified sections, the train drive system 100 connects the battery system 121 in series, raises the voltage close to the overhead line voltage, and supplies it to the inverter 116 and the static inverter 117. During regeneration, the DC power output from the inverter 116 is charged to the battery system 121. The pantograph 112 is lowered (off) to separate it from the overhead line. The main circuit contactor 114 is on the required path and is in a conductive (on) state. The battery system contactor 123 is on the required path and is in a conductive (on) state. In order for the battery system 121 to have a voltage similar to that of the overhead line 111, the series contactor 121C is in a conductive (on) state, and the parallel contactors 121d and 121e are in an open (off) state. Even if no contactor is provided between the storage battery high speed circuit breaker 124 and the step-down DC/DC converter 122, the step-down DC/DC converter 122 is cut off by opening the switch element 122a.

In the non-electrified section under conditions No. 7 to 12 shown in FIG. 6, the chargeable state and operating state are different, and the converter/inverter operation is different. The static inverter 117 is always operating under conditions No. 7 to 12. The step-down DC/DC converter 122 is always off and in a current cut-off state under conditions No. 7 to 12. Under conditions No. 7 to 12, all power consumed by the vehicle is supplied from the storage battery system 121 or from regenerative power, and the storage battery system 121 is discharging, charging, or stopped.

No. 7 is a case where the battery is not fully charged in a non-electrified section and the operation state is powered. At this time, the train drive system 100 powers the induction motor 118 using the storage battery power, and the storage battery system 121 discharges in series. Therefore, the inverter 116 is turned on and supplies three-phase AC power to power the induction motor 118.

No. 8 is a case where the battery is fully charged and the train is in a powered running state in a non-electrified section. At this time, the operation of the train drive system 100 is the same as No. 7.

No. 9 is a case where the battery is not fully charged in a non-electrified section and the train is coasting or stopped. At this time, the train drive system 100 does not operate the induction motor 118, and the battery system 121 discharges in series. Therefore, the inverter 116 is turned off.

No. 10 is a case where the battery is fully charged in a non-electrified section, and the train is coasting or stopped. At this time, the operation of the railcar traction system 100 is equivalent to No. 9.

No. 11 is a case where the battery is not fully charged in a non-electrified section and the operating state is a regenerative state. At this time, the train drive system 100 operates the induction motor 118 in a regenerative manner, and the storage battery system 121 charges in series. Therefore, the inverter 116 is turned on, and the regenerative three-phase AC power is obtained from the induction motor 118 and converted into DC power.

No. 12 is a case where the battery is fully charged in a non-electrified section and the operation state is regenerative. At this time, the battery system that receives the regenerative power cannot be charged, so the train drive system 100 brakes the train using a different type of brake such as an air brake (not shown) rather than the regenerative operation of the induction motor 118. The battery system 121 discharges in series due to the operation of the static inverter 117.

By controlling the 12 different conditions described above, the railway vehicle drive system 100 is capable of powering, coasting, stopping, and regenerative operation in electrified and non-electrified sections depending on the chargeable state of the storage battery system 121.

Figure 9 is a diagram showing, in tabular form, the sequence when the traction system 100 for a railway vehicle according to the first embodiment switches the circuit state from an electrified section to a non-electrified section. Here, the subject of operation for each step constituting the sequence is the control device 130, but in the following, the notation of the subject of operation will be omitted.

Step 1 is the switching start state step. When switching starts, the vehicle must be on the electrified section. At this time, the circuit state of the traction system 100 for the railway vehicle is the same as No. 4 shown in Figure 6.

In step 2, the static inverter 117 is turned off. Here, the control device 130 and each pantograph and contactor can be operated by a storage battery for control equipment (not shown).

In Step 3 , the pantograph 112 is turned off (lowered) to disconnect the railcar traction system 100 from the DC overhead line 111 .
In Step 4, the main circuit contactor 114 is turned off.

In Step 5, the parallel contactors 121d and 121e are turned off to separate the storage battery units.
In Step 6, the series contactor 121c is turned on to connect the storage battery units in series.

In step 7, the storage battery system contactor 123 is turned on, and the voltage of the storage battery system 121 is drawn to the main circuit contactor 114.

In step 8, the storage battery system 121 is turned on and the voltage of the storage battery system 121 is applied to the DC electric train drive system 110.

In step 9, the static inverter 117 is turned on to complete the switching. At this time, the circuit state of the traction system 100 for a railway vehicle is the same as No. 10 shown in FIG.

Figure 10 is a diagram showing, in tabular form, the sequence when the traction system 100 for a railway vehicle according to Example 1 switches the circuit state from a non-electrified section to an electrified section. Here, the subject of operation for each step constituting the sequence is the control device 130, but in the following, the notation of the subject of operation will be omitted.

Step 1 is the switching start state step. When switching starts, the vehicle must be on the electrified section. At this time, the circuit state of the traction system 100 for the railway vehicle is the same as No. 10 shown in FIG. 6.

In step 2, the static inverter 117 is turned off. At this point, the power supply for the auxiliary equipment is cut off, but the control device 130, the pantographs, and the contactors can be operated by a storage battery for control equipment (not shown).

In Step 3 , the storage battery system contactor 123 is turned off, and the voltage of the storage battery system 121 is cut off from the DC electric railcar traction system 110 .
In Step 4, the main circuit contactor 114 is turned off.

In Step 5, the series contactor 121c is turned off to separate the storage battery units.
In Step 6, the parallel contactors 121d and 121e are turned on to connect the storage battery units in parallel.

In step 7, the pantograph 112 is turned on (raised) to connect the railway vehicle drive system 100 to the DC overhead line 111.

In step 8, the main circuit contactor 114 is turned on, and the railway vehicle drive system 100 is connected to the DC overhead line 111.

In Step 9, the static inverter 117 is operated and the switching is completed. At this time, the circuit state of the traction system 100 for a railway vehicle is the same as No. 5 shown in FIG.

Next, in order to explain the effects of the first embodiment, a description will be given of charging and discharging of a general storage battery, which is the premise of the first embodiment.
11 is a diagram showing the simplest voltage equivalent circuit 400 of a storage battery system. Any storage battery system can be expressed by the voltage equivalent circuit 400 regardless of the number of internal storage battery cells connected in series or parallel.

The voltage equivalent circuit 400 has a composite ideal battery 401 and a composite battery resistor 402. The composite ideal battery 401 has an open circuit voltage OCV and a charge capacity Q according to the number of batteries connected in series inside. The open circuit voltage OCV is the voltage when no current flows through the storage battery, and is a function of the charging rate SOC of the composite ideal battery. The charging rate SOC is an index indicating the ratio of the charge remaining in the battery to the charge capacity, and can be defined by the following (Equation 1) if the SOC at the start of battery use is SOC0.

The combined battery resistance R is a combined resistance that combines the internal cell resistance and wiring resistance inside the battery system, and is a value that corresponds to the series-parallel configuration of the cells. In addition, the combined battery resistance R is generally a complex function that depends on the battery temperature, battery charging rate, current value, and current flow time, but this will not be discussed here.

Now, the closed circuit voltage CCV, which is the terminal voltage of the storage battery system, can be defined by the following (Equation 2) using the open circuit voltage OCV, the charging rate SOC, the combined battery resistance R and the current I (charging is positive and discharging is negative).

Here, there are two facts related to the first embodiment indicated by (Equation 2) as follows.
First, to charge the battery system, it is necessary to apply a closed circuit voltage CCV that is equal to or greater than the open circuit voltage OCV at the target charging rate SOC, and since the charging rate is the current value itself, the charging rate is proportional to the difference between the closed circuit voltage CCV and the open circuit voltage OCV.
Secondly, in order for the battery storage system to output a current I through a closed circuit CCV, which is the target output voltage, the OCV must be equal to or higher than the target output voltage, taking into account the voltage drop RI.

Based on the above explanation of FIG. 11, the effect of the present invention will be explained with reference to FIG.
Fig. 12 is a diagram showing voltage relationships to show the effects of Example 1. From the left, each bar graph shows an overhead line voltage 201, a voltage 202 of the storage battery system in a 2-series 1-parallel configuration, and a voltage 203 of the storage battery system in a 1-series 2-parallel configuration. Here, the voltages of the storage battery system shown in Fig. 12 are closed circuit voltages.

The overhead line voltage 201 does not always operate at the rated voltage Vpan,rated, but fluctuates between a minimum voltage Vpan,min and a maximum voltage Vpan,max depending on the balance of power supply and demand, such as the power supply of the substation connected by the overhead line and the powering or regenerative status of other vehicles.

The storage battery system 121 has storage battery units 121a and 121b, and assuming that the internal structure of each is the same, the storage battery generally has a closed circuit voltage according to the storage battery's charging rate and current, as shown in (Equation 2). Therefore, the storage battery unit does not always operate at the rated voltage Vuni,rated, but fluctuates to a minimum voltage Vuni,min and a maximum voltage Vuni,max. The rated voltage Vuni,rated of the storage battery is the open circuit voltage at the target charging rate of the storage battery. Vuni,min and Vuni,max are the minimum and maximum closed circuit voltages that take into account the safety and lifespan of the storage battery system, and are approximately equal to the open circuit voltages when the charging rate is minimum and maximum.

In the electrified section, the voltage of the battery system has the voltage 203 of the battery system in the 1-series, 2-parallel configuration, so the voltage of the battery system 121 is the same as the voltage of the battery unit, and fluctuates from the minimum voltage Vuni,min to the maximum voltage Vuni,max at the rated voltage Vuni,rated. The important point here is that, as shown in (Equation 3), the maximum voltage Vuni,max of the voltage 203 of the battery system in the 1-series, 2-parallel configuration is lower than the minimum value Vpan,min of the overhead line voltage 201.

By satisfying the voltage relationship shown in (Equation 3), the railway vehicle drive system 100 of Example 1 is capable of charging the storage battery system 121 to any voltage from the maximum charging rate to the minimum charging rate, simply by stepping down the voltage of the DC overhead line 111 using the step-down DC/DC converter 122, even if the voltage of the DC overhead line 111 fluctuates.

This eliminates the need to use a step-up step-down DC/DC converter instead of the step-down DC/DC converter 122, simplifying the circuit and improving power conversion efficiency. Note that when the voltage relationship shown in (Equation 3) cannot be achieved due to the battery configuration and the voltage relationship shown in (Equation 4) is achieved, the battery storage system can charge up to the charge rate of the open circuit voltage corresponding to the fluctuating pantograph voltage.

On the other hand, since the voltage of the battery system in the non-electrified section is the voltage 202 of the battery system in the case of 2 series 1 parallel configuration, the voltage of the battery system 121 is equal to twice the voltage of the battery unit and fluctuates from a minimum voltage 2Vuni,min to a maximum voltage 2Vuni,max at a rated voltage 2Vuni,rated.

In general, inverter 116 and static inverter 117 are designed to maximize power conversion efficiency at the rated value Vpan,rated of overhead line voltage 201, but they also operate within a normally fluctuating overhead line voltage. Therefore, the voltage 202 of the storage battery system in 2 series 1 parallel configuration defined by (Equation 2) may be such that the closed circuit voltage CCV defined by (Equation 5) is approximately between the minimum voltage Vpan,min and the maximum voltage Vpan,max.

As described above, the storage battery system 121 can operate the inverter 116 and the static inverter 117 with its own DC voltage without transformation, which allows for a simpler circuit and improved power conversion efficiency compared to a circuit having a DC/DC converter.

In the first embodiment, the present invention is applied to a DC electric railcar drive system that is driven by a DC overhead line 111, but the present invention is also applicable to a railway vehicle drive system that uses an AC overhead line.
FIG. 13 is a diagram showing a configuration in which the DC electric railcar drive system 110 of the railcar drive system 100 shown in FIG. 1 is replaced with an AC electric railcar drive system 110'.

The AC electric train drive system 110' is a conventional drive system for an AC electric train for running on an electrified section of an AC overhead line. The drive system 100 for a rail vehicle is connected to the AC overhead line 111' via a pantograph 112 to take in AC power. The AC power passes through the overhead line high-speed circuit breaker 113 and is transformed into AC power via a transformer 160. The transformed AC power is converted into DC power by an AC/DC converter 150.

The configuration of the AC electric train drive system 110' after conversion to DC power is the same as that of the DC electric train drive system 110. In such a circuit, in the electrified section, a constant DC voltage that is not affected by fluctuations in the overhead lines is output from the AC/DC converter 150, but is output at the optimal operating point voltage of the inverter 116 and the static inverter 117.

As mentioned above, it is desirable to set the open circuit voltage of the storage battery system 121 to a voltage higher than the optimal operating point voltage of the inverter, etc., taking into account the voltage drop shown in (Equation 2). Here, if the storage battery system 121 is a battery without normal series-parallel switching, a step-up/step-down DC/DC converter that can continuously control the output voltage of the AC/DC converter 150 from low voltages to high voltages is required for charging control of the storage battery.

However, by implementing the series-parallel switching of the power storage unit according to the present invention, charging can be controlled only by the step-down DC/DC converter 122, simplifying the circuit. In this way, the present invention is not limited to railway vehicle drive systems with DC overhead lines, but also has the same effect on railway vehicle drive systems with AC overhead lines.

Further, although the present invention is applied to a train that takes in power from an overhead line in the embodiments shown in Figs. 1 and 13, the present invention can also be applied to an electric diesel railcar that generates power using an engine and is driven by a motor 118.
FIG. 14 is a diagram showing a configuration in which the DC electric railcar drive system 110 of the railcar drive system 100 shown in FIG. 1 is replaced with an electric diesel railcar drive system 110''.

The electric diesel railcar drive system 110'' is a conventional drive system for running on non-electrified sections. The railcar drive system 100 generates three-phase AC power by rotating a generator 180 with the torque generated by an engine 170. The AC power is converted to DC power by an AC/DC converter 150. After being converted to DC power, the configuration of the electric diesel railcar drive system 110'' is the same as that of the DC electric railcar drive system 110. A vehicle that combines an electric diesel railcar with a storage battery in this way is called a "hybrid diesel railcar."

Furthermore, the "engine 170 + generator 180 + AC/DC converter 150" configuration of the electric diesel railcar drive system 110'' shown in Figure 14 can be replaced with a fuel cell, making it possible to configure it as an alternative to the DC electric railcar drive system 110.

The advantage of applying the present invention to the electric diesel railcar shown in Figure 14 is that, similar to the application to the AC electric railcar shown in Figure 13, by implementing series-parallel switching of the storage unit according to the present invention, charging can be controlled only by the step-down DC/DC converter 122, simplifying the circuit. In this way, the present invention has the same effect on the railway vehicle drive system of an electric diesel railcar.

In addition, the generator 180 and engine 170 of the electric diesel railcar drive system shown in Fig. 14 may be connected in parallel to the AC/DC converter 150 in the railway vehicle drive system for AC electric railcars shown in Fig. 13. This results in a main circuit configuration that can drive the train as an AC electric railcar, as an electric diesel railcar, and as a battery electric railcar.

In Example 1, the step-down DC/DC converter 122 is configured to be capable of flowing only the unidirectional step-down current shown in FIG. 3, and it is sufficient for the step-down DC/DC converter 122 to operate to flow current only in the charging direction of the storage battery system 121, but it may also be, for example, a bidirectional step-down DC/DC converter 122x that can flow current in both directions.

Figure 15 is a diagram showing the circuit configuration of a bidirectional step-down DC/DC converter 122x according to the first embodiment. The bidirectional step-down DC/DC converter 122x differs from the unidirectional step-down DC/DC converter 122 shown in Figure 3 in that it adds a semiconductor switch (SW2) 122e, a diode (D2) 122f, a capacitor (C2) 122g, and a converter contactor (CK) 122h. However, the capacitor 122g is an element for flattening the ripple voltage, and is not necessarily required depending on the nature of the load.

With this configuration, the bidirectional step-down DC/DC converter 122x can pass current not only in the direction of charging the storage battery system 121 (current is input from the P terminal and current is output from the PLow terminal), but also in the direction of discharging (current is output from the P terminal and current is input from the PLow terminal). However, in this case, the voltage magnitude relationship in which the voltage of the PLow terminal is lower than that of the P terminal does not change, so voltage boost is not possible.

The effects achieved by using the bidirectional step-down DC/DC converter 122x are as follows.
First, even if the vehicle runs using the circuit configuration in the non-electrified section shown in FIG. 8 and unintentionally reaches a charged state above the SOC defined as a fully charged state due to regenerative power, and then enters an electrified section and switches to the circuit configuration shown in FIG. 7, the excess charged amount can be boosted by the bidirectional step-down DC/DC converter 122x and discharged to the DC electric railcar drive system 110, thereby reducing the charged amount and contributing to the safety and life extension of the battery.

Secondly, even if the SOC drops unintentionally while running using the circuit configuration in the non-electrified section shown in Figure 8 and the voltage of the battery system 121 falls below the voltage that would operate the DC electric train drive system 110 directly without transformation, it has the effect of enabling running in places where running is normally not possible. At this time, the battery system 121 remains in a series state, the battery system contactor 123 is opened, and the low-voltage voltage of the battery system 121 is boosted using the bidirectional step-down DC/DC converter 122x, making it possible to operate the DC electric train drive system 110.

Thirdly, if the parallel contactors 121d and 121e fail in a non-electrified section and are welded together in a conductive state, fixing the parallel state, it is possible to open the series contactor 121c and the storage battery system contactor 123, and use the bidirectional step-down DC/DC converter 122x to boost the voltage of the low-voltage storage battery system 121, thereby operating the DC electric train drive system 110.

Fourth, if either the storage battery unit 121a or 121b becomes unusable in a non-electrified section, it is possible to run on a section where it would normally be impossible to run on only one of the storage battery units. For example, if the storage battery unit 121b fails, the series contactor 121c and the parallel contactor 121d are opened, the parallel contactor 121e is made conductive, and the storage battery system 121 is placed in a state where only the storage battery unit 121a is used. The voltage of the low-voltage storage battery system 121 is boosted using the bidirectional step-down DC/DC converter 122x, making it possible to operate the DC electric train drive system 110.

However, due to the presence of diode 122f, bidirectional step-down DC/DC converter 122x cannot be shut off when the voltage at the PLoW terminal is higher than that at the P terminal. For this reason, bidirectional step-down DC/DC converter 122x has converter contactor 122h. Converter contactor 122h is conductive and operates bidirectional step-down DC/DC converter 122x in the circuit configuration of the electrified section shown in Figure 7, but is open and shuts off bidirectional step-down DC/DC converter 122x in the circuit configuration of the non-electrified section shown in Figure 8. Converter contactor 122h always performs opening and closing operations in the opposite direction to that of storage battery system contactor 123.

In Example 1, the storage battery system 121 switches to a low-voltage state circuit shown in Figure 7 in the electrified section, and by making the maximum voltage of the storage battery system shown in Figure 12 lower than the minimum voltage of the overhead line, it is possible to charge using only the step-down operation of the step-down DC/DC converter 122.
In contrast, in Example 2, the storage battery system 121 switches to a high-voltage state circuit in the electrified section, and by making the minimum voltage of the storage battery system higher than the maximum voltage of the overhead lines, it is possible to charge using only the boost operation of the boost DC/DC converter.

Figure 16 is a diagram showing the system configuration of a drive system 100' for boost charging type railway vehicles according to Example 2 of the present invention. The configuration of the drive system 100' for boost charging type railway vehicles is the same as that of the drive system 100 for railway vehicles according to Example 1 shown in Figure 1, except that the step-down DC/DC converter 122 is replaced by a step-up DC/DC converter 122y. In Example 1, the storage battery units 121a and 121b had a voltage equivalent to the DC overhead line 111 when connected in series as the voltage of the storage battery system 121, but in Example 2, each storage battery unit has a voltage equivalent to the DC overhead line 111.

The step-up DC/DC converter 122y is a device that converts input DC power into high DC voltage power and outputs it. The step-down DC/DC converter 122 has external connection terminals P, N, and PHigh, and outputs the DC voltage between P and N by boosting it between PHigh and N. The internal circuit of the step-up DC/DC converter 122y is different from that of the step-down DC/DC converter 122, but will not be described in detail as it is not the essence of the present invention.

17 is a diagram showing a control table of a boost charge type railway vehicle traction system 100' according to Example 2. The configuration of the control device 130 is the same as that of Example 1, and therefore will not be described.
In the control table, the operation of the pantograph and contactor is determined by whether the section is electrified or non-electrified, and in electrified sections, the circuit configuration is switched to one that receives overhead power, and in non-electrified sections, the circuit configuration is switched to one that allows the train to run on power from the battery system 121.

The control table for Example 2 shown in Figure 17 is identical to the control table for Example 1 shown in Figure 6, except that the opening and closing operations of the series contactor 121C and the parallel contactors 121d and 121e are reversed.

Figure 18 is a circuit diagram 100'a in an electrified section of a drive system 100' for a boost charging type railway vehicle according to Example 2. In the electrified section (conditions 1 to 6 shown in Figure 17), the circuit state is the same as that of circuit diagram 100'a shown in Figure 18. In the figure, solid lines indicate conductive parts of the circuit, and dotted lines indicate open parts of the circuit.

In electrified sections, the following connections will be made:
In the boost charging railway vehicle traction system 100′, DC power from the overhead line 111 is supplied to an inverter 116 and a static inverter 117, and is boosted by a boost DC/DC converter 122y to charge the storage battery system 121 with a boosted voltage in a series connection.

The pantograph 112 is raised (on) to receive power from the overhead line.
The main circuit contactor 114 is on the required path and is in the conductive (ON) state.
If the storage battery system contactor 123 were to be conductive, the overhead line voltage would be directly applied to the storage battery system 121, making it impossible to control the charging rate and the final charging voltage, and therefore the storage battery system contactor 123 is set to an open (off) state.

In order for the storage battery system 121 to have a lower voltage than the overhead line 111, the series contactor 121C is set to a conductive (ON) state, and the parallel contactors 121d and 121e are set to an open (OFF) state.

Converter/inverter operation and battery charge/discharge operation in conditions No. 1 to 6 in the electrified section shown in Figure 17 are the same as in Example 1.

Figure 19 is a circuit diagram 100'b in a non-electrified section of a drive system 100' for a boost charging type railway vehicle according to Example 2. In a non-electrified section (conditions No. 7 to 12 shown in Figure 15), the circuit state is the same as that of circuit diagram 100'b shown in Figure 19. In the figure, solid lines indicate conductive parts of the circuit, and dotted lines indicate open parts of the circuit.

In non-electrified sections, the connections are as follows:
The drive system 100' for a boost charging type railway vehicle has a storage battery system 121 in a parallel state, reduces the voltage to close to the overhead line voltage, and supplies it to the inverter 116 and the static inverter 117, and during regeneration, the DC power output from the inverter 116 is charged in the storage battery system 121.

The pantograph 112 is lowered (off) to separate from the overhead line.
The main circuit contactor 114 is on the required path and is in the conductive (ON) state.
The battery system contactor 123 is on the required path and is in a conductive (ON) state.

In order for the storage battery system 121 to have a voltage similar to that of the overhead line 111, the series contactor 121C is set to an open (OFF) state, and the parallel contactors 121d and 121e are set to a conductive (ON) state.

The step-up DC/DC converter 122y is in an open state due to an internal switch element being open or a converter contactor.

The converter/inverter operation and battery charge/discharge operation in conditions No. 7 to 12 in the non-electrified section shown in Figure 17 are the same as those in Example 1.

Figure 20 is a diagram showing voltage relationships to demonstrate the effects of Example 2. From the left, each bar graph shows the overhead line voltage 201, the voltage of the battery system in a 2-series 1-parallel configuration 202, and the voltage of the battery system in a 1-series 2-parallel configuration 203. Here, the voltage of the battery system shown in Figure 20 is the closed circuit voltage.

In the electrified section, the voltage of the battery system has the voltage 202 of the battery system in 2 series 1 parallel configuration, so the voltage of the battery system 121 is equal to twice the voltage of the battery unit, and fluctuates from a minimum voltage 2Vuni,min to a maximum voltage 2Vuni,max at a rated voltage 2Vuni,rated. The important point here is that, as shown in (Equation 6), the minimum voltage 2Vuni,min of the voltage 202 of the battery system in 2 series 1 parallel configuration exceeds the maximum voltage Vpan,mxn of the overhead line voltage 201.

By satisfying the relationship shown in (Equation 6), the drive system 100' for a boost charging type railway vehicle of Example 2 is capable of charging the storage battery system 121 to any voltage from the maximum charging rate to the minimum charging rate, simply by boosting the voltage of the DC overhead line 111 using the boost DC/DC converter 122y, even if the voltage of the DC overhead line 111 fluctuates.

This eliminates the need to use a step-up/step-down DC/DC converter instead of the step-up DC/DC converter 122y, simplifying the circuit and improving power conversion efficiency. Note that when the voltage relationship shown in (Equation 6) cannot be achieved due to the battery configuration and the voltage relationship shown in (Equation 7) is achieved, the battery storage system can charge up to the charge rate of the open circuit voltage corresponding to the fluctuating pantograph voltage.

On the other hand, in non-electrified sections, the voltage of the battery system has the voltage 203 of the battery system in the case of 1 series, 2 parallel, so the voltage of the battery system is the same as the voltage of the battery unit and fluctuates from the minimum voltage Vuni,min to the maximum voltage Vuni,max at the rated voltage Vuni,rated.

In general, inverter 116 and static inverter 117 are designed to maximize power conversion efficiency at the rated value Vpan,rated of overhead line voltage 201, but they also operate within a normally fluctuating overhead line voltage. Therefore, as in the first embodiment, the voltage 203 of the storage battery system in 1 series 2 parallel configuration defined by (Equation 2) should be such that the closed circuit voltage CCV defined by (Equation 5) is roughly between the minimum voltage Vpan,min and the maximum voltage Vpan,max.

As described above, the storage battery system 121 can operate the inverter 116 and the static inverter 117 with its own DC voltage without transformation, which allows for a simpler circuit and improved power conversion efficiency compared to a circuit having a DC/DC converter.

Figure 21 is a diagram comparing the current and voltage of the storage battery system 121 in Example 1 and Example 2. Here, we consider a case in which the drive voltage of the DC electric train drive system 110 is V, charging is performed with power W and current I (W = VI) in electrified sections, and similarly discharging is performed with power -W and current -I (W = VI) in non-electrified sections. Note that to simplify the calculation of current and voltage values, voltage loss due to battery resistance and conversion loss of the DC/DC converter are not taken into account.

In the first and second embodiments, when the input/output power of the storage battery system 121 is the same and the total number of storage battery cells included in the storage battery system 121 is the same, the voltage and current values of each cell are the same.
However, even if the voltage and current values of the storage battery system 121 are different, each has its own suitable application.

First, in non-electrified sections, the storage battery system 121 according to the present invention directly operates the DC electric railcar drive system 110 without transformation, and therefore outputs a voltage V and a current I, respectively. In Example 1, two storage battery units are connected in a 2-series 1-parallel configuration, so that a voltage of V/2 and a current of I flow through each unit. On the other hand, in Example 2, two storage battery units are connected in a 1-series 2-parallel configuration, so that a voltage of V and a current of I/2 flow through each unit.

Next, in the electrified section, the storage battery system 121 according to the present invention transforms and charges the DC electric train drive system 110. In the first embodiment, the storage battery system 121 steps down the voltage to connect the storage battery units in a 1-series, 2-parallel configuration, and is charged with a voltage of V/2 and a current of 2I, with each unit being subjected to a voltage of V/2 and a current of I flowing. On the other hand, in the second embodiment, the storage battery system 121 steps up the voltage to connect the storage battery units in a 2-series, 1-parallel configuration, and is charged with a voltage of 2V and a current of I/2, with each unit being subjected to a voltage of V and a current of I/2 flowing.

From the above, the method of selecting between Example 1 and Example 2 is to choose Example 1 when it is desired to lower the insulation voltage required for the storage battery system 121 and the DC/DC converter 122, and to choose Example 2 when it is desired to lower the current of the external connection part of the storage battery system 121 and the DC/DC converter 122.

In addition, the boost charging type railway vehicle drive system 100' of Example 2 can also be applied to the AC electric train system shown in Figure 13 and the electric diesel railcar drive system shown in Figure 14, in which case the respective step-down DC/DC converters 122 are replaced with step-up DC/DC converters 122y.

In the first and second embodiments, the two storage battery units 1 (hereinafter abbreviated as "BT1") 121a and 2 (hereinafter abbreviated as "BT2") 121b of the storage battery system 121 have the same internal configuration. In this configuration, the voltages of the multiple storage battery units are always the same when traveling in both electrified and non-electrified sections, so no cross currents occur between the units even when the units are connected in parallel.

Example 3 is directed to a general case in which the internal configurations of the storage battery units are different. Note that, although the number of storage battery units is two in Example 3, this is not limited thereto, and the number of storage battery units may be any number equal to or greater than two, as in the configuration shown in FIG. 2.

22 is a diagram showing the cross current when power supplies are connected in parallel. In general, when power supplies V1 and V2 with different voltages are connected in parallel, the cross current Icro is expressed by (Equation 8) based on the voltage difference ΔV=V1-V2 and the combined resistance Rpar of the closed circuit connecting the parallel power supplies.

For example, the cross current calculated by (Equation 8) is a large current value of several hundred amperes, even if two storage battery cells are connected with a difference of 1 V, because the internal resistance of a normal storage battery cell is several milliohms, which is a safety hazard for the battery. Therefore, the cross current needs to be kept below the allowable value for the battery.

Figure 23 is a diagram showing battery units with different internal states according to Example 3. The battery cell 121a1 on the BT1 side has a cell charge capacity Qc1 at a cell voltage Vc1, and the battery cell 121b1 on the BT2 side has a cell charge capacity Qc2 at a cell voltage Vc2.

Here, BT1 is a connection configuration in which the storage battery cells 121a1 are arranged in an S1-direction and a P1-direction, and BT2 is a connection configuration in which the storage battery cells 121b1 are arranged in an S2-direction and a P2-direction. Therefore, the unit voltage Vu1 and the unit charge capacity Qu1 of BT1, and the unit voltage Vu2 and the unit charge capacity Qu2 of BT2 are defined by the following (Equation 9).

Because the storage battery cell 121a1 and the storage battery cell 121b1 have a series switching point 304 of the parallel switching point 303 described later, cells having different SOC-OCV curves are required. In addition, the charging rates of the cells inside BT1 and inside BT2 may be changed.

BT1 and BT2 shown in Figure 23 use different cells and have different unit hardware structures, so they generally have different dielectric strength voltages Viso,1 and Viso,2. As shown in Figure 8, when BT1 and BT2 are connected in series, BT1 has a higher potential with respect to ground point 119, so by using a storage battery unit with a high dielectric strength voltage for BT1, the dielectric strength voltage of the entire storage battery system can be improved.

Figure 24 is a graph showing OCV-accumulated current-SOC for parallel switching control in the low-voltage charging configuration in Example 3. The low-voltage charging configuration is a configuration in which the voltage of the storage battery system 121 is lowered in the electrified section for charging, as in Example 1. In the graph shown in Figure 24, the vertical axis represents the open circuit voltage OCV of each unit, the lower horizontal axis represents the current accumulated value ∫Idt starting from the moment of switching from the 2-series 1-parallel configuration to the 1-series 2-parallel configuration, and the upper horizontal axis represents the charging rate SOC1 of BT1 and the charging rate SOC2 of BT2.

As shown in FIG. 24, BT1 and BT2 have different OCV-accumulated current curve characteristics, and therefore curve 301 (solid curve) of BT1 and curve 302 (dashed curve) of BT2 are different. Whether the storage battery system 121 is in a series or parallel state, the state of each storage battery unit BT1 and BT2 follows the graph shown in FIG. 24. In terms of the OCV-accumulated current relationship, curve 301 of BT1 and curve 302 of BT2 must intersect at least two points, with parallel switching point 303 and series switching point 304 as the intersection points.

First, consider the case where the vehicle is in an electrified section and BT1 and BT2 of the storage battery system 121 are in parallel. Parallel switching from a series configuration in a non-electrified section to a parallel configuration in an electrified section is performed at the parallel switching voltage OCVmin at parallel switching point 303 in the diagram. At parallel switching point 303, the open circuit voltages of BT1 and BT2 are the same, so no cross current occurs when switching from a series configuration to a parallel configuration.

Voltage adjustment of the intersection point OCVmin is possible within a certain range by selecting the cell type of BT1 and BT2, the number of series/parallel cells, and the SOC. When the non-electrified section is connected in series, the battery system 121 sets 2OCVmin as the minimum series voltage. This is because when charging and discharging the battery system 121 and adjusting the voltage to the voltage of the parallel switching point 303, the charging power is only regenerated in the non-electrified section, and it is possible that voltage adjustment is not possible in the charging direction. On the other hand, in the discharging direction, it is possible to reach the voltage of the parallel switching point 303 by discharging alone from any charging state by using a load inside the vehicle. Note that the SOC-OCV curves are generally different between BT1 and BT2, so the charging rate SOCmin,1 of BT1 and the charging rate SOCmin,2 of BT2 at OCVmin are generally different.

Now, in the electrified section, BT1 and BT2 are charged in parallel from the voltage of the parallel switching point 303. At this time, BT1 and BT2 are in parallel, the CCVs are always at the same voltage, and even if the OCVs temporarily mismatch according to (Equation 2), the charging current I is suppressed by constant voltage charging.

Just before charging is completed, the OCVs of BT1 and BT2 automatically match. At this time, the integral current value ∫Idt flowing through BT1 and BT2 is determined by the charge capacities Q_u1 and Q_u2 of BT1 and BT2 and the SOC-OCV curves of BT1 and BT2, and generally do not match. Therefore, charging stops at series switching point 304, which is the second intersection point of the OCV-integrated current curves of BT1 and BT2.

The accumulated current from the parallel switching point 303 to the series switching point 304 is ΔQ. If the series switching of the circuit is performed at a point other than the series switching point 304, the accumulated currents flowing through the two units BT1 and BT2 generally do not match.

After the open circuit voltage of BT1 and BT2 reaches the series switching point 304, the storage battery system 121 switches the circuit to series. After the switching, the storage battery unit discharges again to the parallel switching point 303 with an integrated current of -ΔQ while repeatedly discharging and regenerative charging in the non-electrified section. During this time, the same current value flows through BT1 and BT2 connected in series. Therefore, if the series switching were performed at a point other than the series switching point 304, the integrated current of each unit from charging to discharging would not match, and it would not be possible to return to the parallel switching point 303, so the series switching must be performed at the series switching point 304.

25 is a diagram showing the functional configuration of the control device 130 according to the embodiment 3. Most of the configuration is the same as that of the control device 130 according to the embodiment 1. The control device 130 according to the embodiment 3 has a changeover determination unit 134 as a difference.
The switching determination unit 134 receives the charging rate of each battery unit output from the battery status management unit 131 and outputs the determination result of whether switching is possible to the main circuit switching control unit 133 and the vehicle control logic unit 132. For this determination, the charging rate information of BT1 and BT2 output from the battery status management unit 131 is used. There is generally a one-to-one correspondence between the charging rate of a battery and the open circuit voltage.

As shown in FIG. 24, when the charging rate of BT1 is SOCmin,1 and the charging rate of BT2 is SOCmin,2, it is in the state of parallel switching point 303, and when the charging rate of BT1 is SOCmax,1 and the charging rate of BT2 is SOCmax,2, it is in the state of series switching point 304.

In the main circuit switching control unit 133 of Example 3, not only the command status of the contactor open/close command and the pantograph up/down command is used to determine whether the above-mentioned switching is possible, and series/parallel switching is performed in accordance with the command only while switching is possible.

In the vehicle control logic unit 132 in Example 3, a determination as to whether switching is possible, a contactor opening/closing command, and a pantograph up/down command are input, and when switching is not possible, charging/discharging is performed so that the open voltage state of BT1 and BT2 of the storage battery system 121 becomes switchable.

When switching from a non-electrified section to an electrified section, if the driver's cab 140 has received a contactor open/close command and a pantograph up/down command to switch from a series configuration to a parallel configuration but switching is not possible, the vehicle control logic unit 132 adjusts the output value of the inverter 116 or static inverter 117, supplies power to a load not shown, and discharges the storage battery system 121 until the state of the parallel switching point 303 is reached.

Similarly, when switching from an electrified section to a non-electrified section, if the driver's cab 140 receives a contactor opening/closing command and a pantograph up/down command to switch from a parallel configuration to a series configuration but the switching is not possible, the vehicle control logic unit 132 adjusts the output value of the step-down DC/DC converter 122 and charges the storage battery system 121 until the state of the series switching point 304 is reached.

Although the third embodiment has been described based on the first embodiment in which charging is performed from an external power source in a parallel state, the basic configuration is the same as that of the second embodiment in which charging is performed from an external power source in a series state. At this time, the parallel switching point 303 and the series switching point 304 shown in FIG. 24 are reversed.
The effect of the third embodiment is that it is possible to switch between series and parallel configurations of storage battery units having different configurations.

In Example 3, the cross current was suppressed by performing parallel switching of the battery system 121 at the point where the open circuit voltages of the battery units match. However, this control makes it difficult to strictly match the open circuit voltages of the battery units, and a certain amount of cross current occurs.

In addition, even if the cell types, series-parallel configuration, and charging rates of the battery cells in each battery unit are designed to be identical, as in Examples 1 and 2, the charge capacities between the battery units will differ due to, for example, differences in the temperature distribution of each battery unit, and the relationship between the OCV and accumulated current will differ between the battery units.

In such a case, there are not necessarily two points where the open circuit voltages are the same as in the third embodiment, and the cross current at the time of parallel switching predicted by (Equation 8) cannot be avoided.
Therefore, in the fourth embodiment, the storage battery system 121 has a cross current suppression circuit.

Figure 26 is a diagram showing a storage battery system 121' having a cross current suppression circuit according to Example 4. In addition to the storage battery system 121, the storage battery system 121' has a cross current suppression resistor (Rcro) 121g and a cross current resistance contactor (BK4) 121f. The cross current resistance contactor 121f shown in Figure 26 is arranged on the positive electrode side, but may be arranged on the negative electrode side.

In the traction system 100 for a railway vehicle according to the fourth embodiment, the configuration other than the storage battery system 121' is the same as that of the first embodiment. The cross current suppression resistor 121g is a resistor having a resistance value Rcro. When the cross current suppression circuit operates, the cross current resistance contactor (BK4) 121f and the negative side parallel contactor (BK3) 121e of the storage battery system 121' are in a conductive (ON) state, and the series contactor (BK1) 121c and the positive side parallel contactor (BK2) 121d are in an open (OFF) state. At this time, the cross current I_cro flowing through each storage battery unit BT1 and BT2 is calculated by the following (Equation 10) using the voltage difference ΔV between the units, the combined resistance Rpar other than the cross current suppression resistor, and the cross current suppression resistor Rcro. The cross current I_cro is suppressed more than in the case of the direct parallel connection of (Equation 9).
I_cro=ΔV/(R_par+R_cro) (Formula 10)
Here, the cross current suppression resistor 121g may be a fixed resistor, but if it is a variable resistor that can be remotely controlled, the resistance value Rcro becomes variable and the cross current I_cro can be controlled, which is preferable.

Because the cross current I_cro flows from the high-voltage battery unit to the low-voltage battery unit, the open-circuit voltage of the high-voltage battery unit decreases as the charging rate decreases, and the open-circuit voltage of the low-voltage battery unit increases as the charging rate increases, and the open-circuit voltages between the battery units approach each other as the cross current decreases. If the resistance value of the cross current suppression resistor 121g is too large, the open-circuit voltage difference between the battery units will not be eliminated for a long time, and conversely, if it is too small, a large cross current will flow. Therefore, the optimal value (Equation 10) is used, which is estimated from the withstand current value of the battery unit and the desired time required to eliminate the voltage difference between the units.

After the open-circuit voltage difference between the two battery units is sufficiently reduced by the cross current, the battery system 121' separates the cross current suppression circuit. At this time, the positive-side parallel contactor (BK2) 121d and the negative-side parallel contactor (BK3) 121e of the battery system 121' are in a conductive (ON) state, and the series contactor (BK1) 121c and the cross current resistance contactor (BK4) 121f are in an open (OFF) state.

Next, a circuit switching sequence of the railway vehicle traction system 100 according to the fourth embodiment will be described taking as an example a case in which a parallel configuration is provided in an electrified section as shown in the first embodiment.
27 is a diagram showing, in the form of a table, a sequence for switching the circuit state from an electrified section to a non-electrified section in the traction system 100 for a railway vehicle according to the fourth embodiment. In this case, the battery system is switched from parallel to series, so no cross current occurs. Therefore, the sequence configuration is the same as that of the first embodiment shown in FIG. 9, and the main operator is the control device 130.

Figure 28 is a diagram showing, in tabular form, a sequence for switching the circuit state from a non-electrified section to an electrified section in the traction system 100 for a railway vehicle according to Example 4. Here, the subject of operation for each step constituting the sequence is the control device 130, but in the following, the subject of operation will be omitted.

In the sequence shown in FIG. 28, steps 1 to 5 are the same as steps 1 to 5 in the first embodiment shown in FIG.
In Step 6, the cross current resistance contactor (BK4) 121f and the negative side parallel contactor (BK3) 121e are turned on.

In Step 7, the open circuit voltages between the storage battery units connected in parallel are equalized by suppressing and safe cross current.
In Step 8, the cross current resistance contactor (BK4) 121f is turned off to isolate the cross current resistance.

In Step 9, the parallel contactor (BK2) 121d on the positive electrode side is turned on to connect BK1 and BK2 in parallel.
Steps 10 to 12 are the same as steps 7 to 9 in the first embodiment shown in FIG.

In the above, the fourth embodiment has been described based on the first embodiment in which the external power source is charged in a parallel state, but the basic configuration of the fourth embodiment is the same as that of the second embodiment in which the external power source is charged in a series state.
The effect of the fourth embodiment is that the storage battery units having different open circuit voltages and generating cross currents can be safely connected in parallel.

In the first to fourth embodiments, the circuit configuration of the traction system 100 for rail vehicles is such that the negative side of each component is grounded at the ground point 119 as shown in FIG. 1. In contrast, in the fifth embodiment, the negative side connection to the ground point 119 shown in FIG. 1 is separated, and each component is grounded at an intermediate voltage. For example, when the total voltage of the battery system is V, the point V/2 is grounded. Although this grounding method complicates the ground circuit, it is possible to halve the voltage to ground of each device, and therefore to relax the insulation design of the device. Note that in the fifth embodiment, the case where the device is installed at a voltage point half the total voltage is shown, but the intermediate voltage does not generally have to be at a voltage point half the total voltage.

In the fifth embodiment, the grounding method of the battery system 121 is mainly discussed, and the grounding method of the other components of the railcar traction system 100 is not particularly discussed. However, the other components also need to be grounded to the same voltage point as the battery system at their respective intermediate voltage points. For example, in order for a device corresponding to a three-level converter to operate normally, the same voltage needs to be applied to the positive half and the negative half of the grounding point. In addition, in general, in order to ground the DC electric train traction system 110 shown in FIG. 1 at the intermediate point, an isolated DC/DC converter is required between the DC electric train traction system 111 and the DC electric train traction system 110 when the power of the DC electric train traction system 111 is taken in by the DC electric train traction system 110, but this will not be described in detail here.

Fig. 29 is a diagram showing the configuration of a series midpoint grounded storage battery system 121α according to Example 5. The storage battery system 121α is the same as the storage battery system 121 shown in Example 1, except that a ground point 119 is provided at the connection between the storage battery unit 121a, the series contactor 121c, and the negative-side parallel contactor 121e.
In this case, when the storage battery system 121α is connected in series, the ground point 119 is located at the midpoint between the storage battery units 121a and 121b, so that voltage is applied to the positive and negative sides from the ground point 119 in other components of the railway vehicle traction system 100 as well.

On the other hand, when the storage battery system 121α is connected in parallel, the ground point 119 is located at the negative point of the storage battery unit 121a and the storage battery unit 121b, so that in the other components of the traction system 100 for the railway vehicle, a voltage is applied to the positive side from the ground point 119, but the negative side is short-circuited, causing the equipment to fail.

Therefore, in the fifth embodiment, a storage battery system in which the midpoint is always grounded is adopted.
FIG. 30 is a diagram showing the configuration of a battery system 121β with a constant midpoint ground. The constant midpoint grounded battery system 121β has three changes from the previous midpoint grounded battery system 121α in series. First, the number of series contactors 121c is two, and a ground point 119 is provided between the two series contactors 121c. Second, each of the parallel units 121a and 121b is a series connection of at least two or more battery units (in FIG. 30, two series connections are provided: 121a1 and 121a2, and 121b1 and 121b2), and the same voltage points are connected via a parallel ground contactor 121h. Third, the number of parallel ground contactors 121h is two, and a ground point 119 is provided between the two parallel ground contactors 121h.

Figure 31 shows the circuit state of the constant-center-grounded battery system 121β in series (high voltage). At this time, the parallel contactors (BK2) 121d and (BK3) 121e3 and the parallel grounding contactors (BK41 and BK42) 121h are in the cutoff (OFF) state, and the series contactors (BK11 and BK12) 121c are in the conductive (ON) state.

That is, the four battery units are connected in series and grounded to ground point 119 between the negative electrode of battery unit (BTa2) 121a2 and the positive electrode of battery unit (BTb1) 121b1, i.e., at the intermediate voltage of the always midpoint grounded battery system 121β.

Figure 32 shows the circuit state of the constant-center-grounded battery system 121β in parallel (low voltage). At this time, the parallel contactors (BK2) 121d and (BK3) 121e and the parallel grounding contactors (BK41 and BK42) 121h are in a conductive (ON) state, and the series contactors (BK11 and BK12) 121c are in a cutoff (OFF) state.

That is, the series connection of the storage battery units (BTa1 and BTa2) 121a1 and 121a2 and the series connection of the storage battery units (BTb1 and BTb2) 121b1 and 121b2 are connected in parallel. Between the negative electrode of the storage battery unit (BTa1) 121a1 and the positive electrode of the storage battery unit (BTa2) 121a2, and also between the negative electrode of the storage battery unit (BTb1) 121b1 and the positive electrode of the storage battery unit (BTb2) 121b2, are always grounded to the ground point 119 at the intermediate voltage of the midpoint grounded storage battery system 121β.

In the constantly midpoint grounded battery system 121β of Example 5, as shown in Figures 31 and 32, the system is grounded to the ground point 119 at the midpoint voltage in both series and parallel connections, so that voltage is applied from the ground point 119 to the positive and negative sides of other components of the traction system 100 for railway vehicles, enabling them to operate normally.

Although various embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit and scope of the present invention.

100...Traction system for railway vehicles, 100a...Traction system circuit for electrified sections, 100b...Traction system circuit for non-electrified sections, 110...DC electric train drive system, 111...DC overhead line, 112...pantograph, 113...overhead high-speed circuit breaker, 114...main circuit contactor, 115...reactor, 116...inverter, 117...static inverter, 117a...AC 440V auxiliary, 117b...AC 100V auxiliary, 117c...DC 100V auxiliary, 118...induction motor, 119...ground point, 120...system for non-electrified sections, 121...storage battery system, 121a, 121 b...storage battery unit, 121c...series contactor, 121d, 121e...parallel contactor, 121c1, 121d1, 121e1...contactor control b-contact, 121c2, 121d2, 121e2...contactor control coil, 122...step-down DC/DC converter, 122a, 122e...semiconductor switch, 122b, 122f...diode, 122c...coil, 122d, 22g...filter capacitor, 122h...converter contactor, 123...storage battery system contactor, 124...storage battery high-speed circuit breaker, 130...control device, 131...storage battery state management unit, 132...vehicle control logic unit, 133... Main circuit switching control unit, 140... cab, 150... AC/DC converter, 160... transformer, 170... engine, 180... generator, 200... voltage diagram, 201... overhead line voltage, 202... voltage of storage battery system when 2 series 1 parallel, 203... voltage of storage battery system when 1 series 2 parallel, 300... OCV-current integral graph, 301... OCV-current integral-SOC curve of BT1, 302... OCV-current integral-SOC curve of BT2, 303... parallel switching point, 304... series switching point, 305... minimum voltage, 401... composite ideal battery, 402... composite battery resistance, 100'... for boost charging type railway vehicle Drive system, 110'...AC electric railcar drive system, 110''...electric diesel railcar drive system, 111'...AC overhead line, 122x...bidirectional step-down DC/DC converter, 122y...step-up DC/DC converter, 121a1, 121b1...storage battery cell, 134...switching determination unit, 121'...storage battery system with cross-current suppression circuit, 121g...cross-current suppression resistor, 121f...cross-current resistor contactor, 121α...series midpoint grounded storage battery system, 121β...constant midpoint grounded storage battery system, 121a1, 121a2, 121b1, 121b2...storage battery unit, 121h...parallel grounding contactor

Claims (21)

a DC power supply unit including a storage battery system and a DC-DC power converter mounted on the railcar;
a DC power supply drive system that is driven by DC power supplied from the DC power supply unit or DC power supplied from an overhead line through a pantograph, a high-speed circuit breaker, a main circuit contactor, and a reactor in this order, and supplies a predetermined power to a load device mounted on the railway vehicle;
a control device for controlling the DC power supply unit and the DC power supply drive system,
the battery system includes a plurality of battery units and a series-parallel switching means that is connected between the high-speed circuit breaker and the main circuit contactor via a battery system contactor and that switches a connection state between the plurality of battery units to a series state or a parallel state;
a control device for a railway vehicle, when switching the supply of DC power from the overhead line to the DC power supply unit, lowers the pantograph from the overhead line, turns off the main circuit contactor, operates the series-parallel switching means to switch the connection state between the multiple storage battery units to a series state, turns on the storage battery system contactor, and turns on the main circuit contactor. 2. A drive system for a rail vehicle according to claim 1,
a control device for a railway vehicle, when switching the supply of DC power from the DC power supply unit to the overhead line, turns off the battery system contactor, turns off the main circuit contactor, operates the series-parallel switching means to switch the connection state between the multiple battery units to a parallel state, raises the pantograph toward the overhead line, and turns on the main circuit contactor. A drive system for a railway vehicle according to claim 1 or 2,
When DC power is supplied from the overhead line,
An output voltage of the storage battery system is a voltage equal to or lower than a DC voltage applied from the overhead line,
The control device controls the DC-DC power converter to step down the DC voltage and charge/discharge the battery system. A drive system for a railway vehicle according to any one of claims 1 to 3,
When the output voltage of the storage battery system falls below a voltage value at which the DC power supply driven system can operate in the series state, or when switching of the series-parallel state becomes impossible,
The control device controls the DC-DC power converter to step down the voltage from the DC power supply drive system to the storage battery system, thereby charging and discharging the storage battery system. (delete) (delete) A drive system for a railway vehicle according to any one of claims 1 to 4,
The control device, when supplying DC power from the DC power supply unit, connects the storage battery system and the DC power supply drive system without going through the DC-DC power converter, and performs charging and discharging between the storage battery system and the DC power supply drive system. (delete) (delete) (delete) A drive system for a railway vehicle according to any one of claims 1 to 4 and 7,
the series/parallel switching means is composed of a series connection contactor and a parallel connection contactor,
13. A drive system for railway vehicles, comprising: a series connection contactor and a parallel connection contactor, the conductive state and the open state of which are mutually exclusive except when switching between the series-parallel state. A drive system for a railway vehicle according to any one of claims 1 to 4, 7 and 11,
The plurality of storage battery units have different dielectric strength voltages,
a storage battery unit having a low withstand voltage is connected to a low-voltage side when the series-parallel switching means switches to the series state. A drive system for a railway vehicle according to any one of claims 1 to 4, 7, 11 and 12,
an open-circuit voltage of each of the different storage battery units among the plurality of storage battery units is equal to two different switching-time open-circuit voltages through charging and discharging when switching between the series state and the parallel state;
a switching state in which the open-circuit voltage of each of the different storage battery units is equal to one of the two different switching-time open-circuit voltages, and the switching state is changed from the series state to the parallel state or from the parallel state to the series state. A drive system for a railway vehicle according to any one of claims 1 to 4, 7, 11 and 12,
a cross current reducing circuit connected between positive electrodes or negative electrodes of the plurality of storage battery units in addition to the series/parallel switching means;
A drive system for a railway vehicle, characterized in that, when switching from the series state to the parallel state by the series-parallel switching means, the control device makes the cross current reduction circuit conductive to form a parallel circuit of the battery units including the cross current reduction circuit to reduce the voltage difference between the battery units, and then opens the cross current reduction circuit to switch to the parallel state excluding the cross current reduction circuit. A drive system for a railway vehicle according to any one of claims 1 to 4, 7 and 11 to 14,
the plurality of storage battery units are configured such that at least two of the storage battery units are connected in series in the parallel state,
the series-parallel switching means is composed of a series connection contactor consisting of two contactors connected in series, a first parallel connection contactor which is a single contactor, and a second parallel connection contactor consisting of two contactors connected in series;
In the series state, the series connection contactor is conductive, the first and second parallel connection contactors are interrupted, and a portion sandwiched between the two contactors constituting the series connection contactor is grounded;
a second parallel connection contactor that connects the two or more storage battery units connected in series to each other, and a portion of the second parallel connection contactor that is sandwiched between the two contactors is grounded. a DC power supply unit mounted on the railway vehicle and including a storage battery system having a plurality of storage battery units and a DC-DC power converter;
a DC power supply drive system that is driven by DC power supplied from the DC power supply unit or DC power supplied from an overhead line through a pantograph, a high-speed circuit breaker, a main circuit contactor and a reactor in this order, and supplies a predetermined power to a load device mounted on the railway vehicle,
the battery system includes a plurality of battery units and a series-parallel switching means that is connected between the high-speed circuit breaker and the main circuit contactor via a battery system contactor and that switches a connection state between the plurality of battery units between a series state and a parallel state;
a driving method for a railway vehicle, characterized in that, when switching the supply of DC power from the overhead line to the DC power supply unit, the pantograph is lowered from the overhead line, the main circuit contactor is turned off, the series-parallel switching means is operated to switch the connection state between the multiple storage battery units to a series state, the storage battery system contactor is turned on, and the main circuit contactor is turned on. (delete) 17. A method for driving a railway vehicle according to claim 16, comprising the steps of:
a series-parallel switching means for switching a connection state between the plurality of battery units to a parallel state, a pantograph being raised toward the overhead line, and a main circuit contactor being turned on when switching a supply of DC power from the DC power supply unit to the overhead line; 19. A drive method for a railway vehicle according to claim 16 or 18, comprising the steps of:
When the output voltage of the storage battery system falls below a voltage value at which the DC power supply driven system can operate in the series state, or when switching between the series state and the parallel state becomes impossible,
a DC-DC power converter is controlled to step down the voltage from the DC power supply drive system to the storage battery system, thereby charging and discharging the storage battery system. A drive method for a railway vehicle according to any one of claims 16, 18 and 19, comprising the steps of:
connecting the positive electrodes or the negative electrodes of the plurality of storage battery units with a cross current reducing circuit;
A driving method for a railway vehicle, characterized in that when switching from the series state to the parallel state by the series-parallel switching means, the cross current reduction circuit is made conductive to form a parallel circuit of the battery units including the cross current reduction circuit to reduce the voltage difference between the battery units, and then the cross current reduction circuit is opened to switch to the parallel state excluding the cross current reduction circuit. A railway vehicle equipped with the drive system for railway vehicles according to any one of claims 1 to 4, 7, and 11 to 15.

Images