JP4334500B2 - Power system - Google Patents

Description

The present invention includes a first power storage device that stores power generated by a power generation device, a second power storage device that stores power having a voltage lower than that of the first power storage device, the first power storage device, and the second power storage. device and electrically connected blockable switching device relates to a power system and a converter provided between said second power storage device and the switching drive of a switching device.

  A power generation apparatus, for example, a fuel cell, supplies a fuel gas (mainly containing hydrogen) and an oxidant gas (mainly oxygen-containing gas) to the anode side electrode and the cathode side electrode to react electrochemically. This is a system for obtaining DC electrical energy.

  For example, a polymer electrolyte fuel cell includes a power generation cell in which an electrolyte membrane / electrode structure provided with an anode side electrode and a cathode side electrode is sandwiched between separators on both sides of an electrolyte membrane made of a polymer ion exchange membrane. ing. This type of power generation cell is normally used as a fuel cell stack by alternately laminating a predetermined number of electrolyte membrane / electrode structures and separators.

  As an application of this type of fuel cell, a fuel cell vehicle mounted on a vehicle such as an automobile has attracted attention. This is because the power generation efficiency is high and the exhaust gas is clean.

  In a fuel cell vehicle, a hybrid power supply system that uses a power storage device such as a battery or a capacitor (electric double layer capacitor) in order to supplement the output responsiveness of the fuel cell is employed. For example, the fuel cell system disclosed in Patent Document 1 includes a fuel cell stack 1 as shown in FIG. 9, and a high-voltage DC / DC converter 2 is connected to a power extraction terminal of the fuel cell stack 1. Has been. On the output side of the DC / DC converter 2 for high power, a secondary battery 3 that stores high voltage (340V), a DC / DC converter 4 for 12V that converts high voltage into 12V, and a motor 5 for traveling A motor inverter 6 that supplies electric power is connected in parallel.

  A 12V battery 7 is connected to the output side of the 12V DC / DC converter 4. The 12V battery 7 includes a power control unit 9 that controls power supplied to the electric heater 8, and a 12V auxiliary machine 10. And are connected.

  The fuel cell system is controlled by the controller 11, and at the time of starting, the ignition switch 12 is rotated to the start position, whereby electric power from the 12V battery 7 is supplied to the controller 11.

Japanese Patent Laid-Open No. 2002-110187 (FIG. 1)

  In Patent Document 1 described above, when the fuel cell system is started, a drive voltage is applied from the 12V battery 7 to the controller 11 and the DC / DC converter 4 for 12V, and a voltage is also applied to other auxiliary machines. . However, the 12V battery 7 cannot secure a desired starting voltage (for example, 9 V or more) when the charge capacity is reduced due to a rise or deterioration of internal resistance at low temperatures, and the fuel cell system is improved. There is a problem that it cannot start.

  The present invention solves this type of problem, and with a simple configuration and control, a desired start-up voltage can be obtained easily and reliably at low temperatures or when deteriorated, and the system can be started up satisfactorily. It is an object to provide a power supply system and a control method thereof.

The present invention provides a power generation device, a first power storage device that stores power generated by the power generation device, a second power storage device that stores power having a voltage lower than that of the first power storage device, and the first power storage device. Between the first power storage device and the downverter, and a downverter provided between the first power storage device and the second power storage device, stepping down the power from the first power storage device and supplying it to the second power storage device A switching device that is capable of electrically connecting and disconnecting the first power storage device and the second power storage device, and that provides power to the switching drive unit from the second power storage device when the system is started , a converter provided between the second power storage device and the switching drive unit, with electric power is applied from the second power storage device, than the voltage setting voltage of the second power storage device to the system startup There upon, and a control device for step-up control of the converter, the driving voltage of the switching drive unit, characterized in that it is set to a voltage higher than the reset voltage of the control device.

  First, when the system is started, the voltage of the second power storage device on the low voltage side is detected. When the detected voltage is lower than the set voltage, the converter is boosted to set the starting voltage applied to the switching drive unit of the switching device high.

  The switching drive unit preferably includes a solenoid, and the drive voltage of the solenoid is preferably set higher than the reset voltage of the control device. Furthermore, it is preferable that the control device outputs a boost command for the converter when a system activation signal is input.

  Furthermore, it is preferable that the control device stops the boost control of the converter when detecting that the switching device is in the conductive state.

  According to the present invention, the voltage of the second power storage device is detected when the system is activated, and the converter is boosted when the detected voltage is lower than the set voltage. For this reason, even if the voltage of the second power storage device decreases due to low temperature or deterioration of the second power storage device, the starting voltage applied to the switching drive unit of the switching device can be maintained high. Thereby, switching failure does not occur, and the power supply system can be reliably and easily started up with a simple configuration and control.

Figure 1 is a schematic illustration of the engagement Ru power system 20 to an exemplary embodiment of the present invention.

  The power supply system 20 is mounted on a fuel cell vehicle (not shown) and includes a fuel cell 22. Although not shown, the fuel cell 22 includes, for example, an electrolyte membrane / electrode structure in which a solid polymer electrolyte membrane is sandwiched between an anode side electrode and a cathode side electrode, and the electrolyte membrane / electrode structure is paired with a pair. It is configured as a stack in which power generation cells sandwiched between separators are stacked.

  The fuel cell 22 is connected to an inverter 24, and the inverter 24 generates three DC power (for example, 300 V) output from the fuel cell 22 and a high-voltage power storage device (first power storage device) 30 described later. It is converted into phase AC power and supplied to the motor 26. The motor 26 allows the fuel cell vehicle to travel by transmitting driving force to both wheels 28.

  The fuel cell 22 is connected to a high voltage power storage device 30 and a switching mechanism, for example, a contactor 32, and the contactor 32 is connected to a downverter (D / V) 34. For example, a low voltage power storage device (second power storage device) 36 that is a 12V battery is connected to the downverter 34.

The low voltage power storage device 36 is connected to a DC-DC converter 38 and other auxiliary machines. The DC-DC converter 38 is connected to a control device 42 via a switching drive unit for driving the contactor 32, for example, a solenoid 40. A voltmeter 44 for detecting the voltage (V _BATT ) of the low voltage power storage device 36 is provided between the DC-DC converter 38 and the solenoid 40.

  The control device 42 controls the entire power supply system 20 and has a function of boosting the DC-DC converter 38 when the voltage of the low-voltage power storage device 36 is lower than the set voltage when the system is activated. The control device 42 receives a start signal from the ignition switch 46.

  As shown in FIG. 2, the DC-DC converter 38 forms a boost circuit, and a coil 50 is disposed on a line 48 to which the voltage of the low-voltage power storage device 36 is input. The output side of the coil 50 is connected to a diode 52 and a gate 54, and the gate 54 is opened and closed by a control circuit 56. A line 58 is connected to the output side of the diode 52, and a capacitor 59 is connected along the line 58.

The control circuit 56 monitors the output voltage (V _BATT ) at the output end of the line 58, and feedback-controls the output voltage when the output voltage is lower than the reference voltage.

  The operation of the power supply system 20 configured as described above will be described below with reference to the timing chart shown in FIG. 3 and the flowcharts shown in FIGS. 4 and 5 in relation to the control method according to the present embodiment. As shown in FIG. 3, the drive lower limit voltage of the solenoid 40 is 9 V, for example, and the reset voltage of the control device 42 is 6 V, for example. The reset voltage is a threshold voltage at which driving of the control device 42 is stopped.

  Here, the energy characteristics and current / voltage characteristics of the low voltage power storage device 36 (hereinafter also simply referred to as a battery) vary between a normal battery and a low temperature or deteriorated abnormal battery as shown in FIG. Yes. For this reason, the intersections P1 and P2 between the battery current and the solenoid drive current, that is, the voltage at the operating point of the solenoid 40 is 9 V or less (intersection P1) in an abnormal battery, and the solenoid 40 is driven. I can't.

  Further, the reset voltage of the control device 42 is set to a voltage (6V) lower than the solenoid drive lower limit voltage (9V). Therefore, as shown in FIG. 7, although the voltage equal to or higher than the reset voltage of the control device 42 is held, the solenoid 40 cannot be driven in the hatched region 60 where the remaining battery capacity is low due to low temperature or deterioration. It is extremely uneconomical.

  Therefore, in the present embodiment, first, when the ignition switch 46 is turned on (step S1 in FIG. 4), a voltage is applied from the low voltage power storage device 36 to the control device 42. Therefore, the control device 42 is turned on and the DC-DC converter 38 is controlled (see step S2 and FIG. 3).

  In the DC-DC converter 38, the gate 54 is opened and closed via the control circuit 56 as shown in FIG. Therefore, while the gate 54 is conducting, energy is stored in the coil 50, while when the gate 54 is opened, the current flowing through the coil 50 is interrupted, and a voltage higher than the input voltage (12V) is generated. The

  The output of the coil 50 is stored in the capacitor 59, and the voltage at both ends of the capacitor 59 is increased by opening and closing the gate 54, and this boosted voltage (for example, 14V) is applied to the solenoid 40. The

  At that time, the control circuit 56 monitors the output voltage and determines whether or not the output voltage is larger than a set voltage (for example, 13 V) (step S11 in FIG. 5). When it is determined that the output voltage is equal to or higher than the set voltage (YES in step S11), the process proceeds to step S12, and the duty ratio of PWM (pulse width modulation) is set small. On the other hand, if it is determined that the output voltage is equal to or lower than the set voltage, that is, if it is determined that there is power consumption by the solenoid 40, the process proceeds to step S13, where the PWM duty ratio is set large.

  As described above, when converter control is performed, the process proceeds to step S3 in FIG. 4 to initialize the control device 42, and further, an ON command for the contactor 32 is output (step S4). For this reason, the contactor 32 is turned on (closed) via the solenoid 40, a high voltage is supplied from the high voltage power storage device 30 to the downverter 34, and the voltage is stepped down by the downverter 34 to charge the low voltage power storage device 36. Done. At this time, an operation signal is output from the downverter 34, and the operation of the downverter 34 is confirmed (YES in step S5).

  When the control device 42 detects that the contactor 32 is in a conducting state based on the operation signal of the downverter 34, the control device 42 stops the boost control of the DC-DC converter 38.

  In this case, in this embodiment, when the power supply system 20 is started up, the voltage of the low-voltage power storage device 36 is detected, and when the detected voltage is lower than the set voltage, the DC-DC converter 38 is boosted. ing.

  Therefore, even if the voltage of the low voltage power storage device 36 decreases due to low temperature start-up or deterioration of the low voltage power storage device 36, the start voltage (output voltage) applied to the solenoid 40 to drive the solenoid 40 is reduced. Can be set high. As a result, the connection failure of the contactor 32 can be reliably prevented, and the power supply system 20 can be started up reliably and easily with a simple configuration and control. In addition, even in the region 60 in FIG. 7, the contactor 32 can be driven, which is advantageous in that it is economical.

  On the other hand, a timing chart of a conventional control method (comparative example) for starting the system without using the DC-DC converter 38 is shown in FIG. The basic operation is the same as the timing chart of the control method of the embodiment shown in FIG.

The output voltage (V _BATT ) is stepped down as power is consumed by the ON signal of the contactor 32, but in a normal battery, the contactor 32 is turned on while maintaining a voltage higher than the solenoid drive lower limit voltage ( In FIG. 8, refer to a two-dot chain line). For this reason, the low voltage power storage device 36 is charged from the high voltage power storage device 30 via the downverter 34, and the low voltage power storage device 36 is boosted.

  However, a low temperature or deteriorated abnormal battery has a small remaining capacity and falls below the solenoid drive lower limit voltage, and the contactor 32 cannot be turned on (refer to the one-dot chain line in FIG. 8). Therefore, in the case of an abnormal battery, the output voltage gradually decreases, drops below the reset voltage of the control device 42, stops the control device 42, and cannot start the system.

  On the other hand, in the present embodiment, the output voltage can be reliably boosted by the DC-DC converter 38 even if the battery is abnormal due to low temperature or deterioration as described above. As a result, it is possible to reliably prevent malfunction of the contactor 32 and perform a good and economical system start-up.

  Although it is conceivable to lower the drive lower limit voltage of the solenoid 40, it is necessary to change the coil constant, change the coil wire diameter, etc., and there is a problem that the solenoid 40 is considerably enlarged and not suitable for practical use. is there.

  In the present embodiment, the contactor 32 is used as a switching mechanism. However, the present invention is not limited to this, and for example, a DC-DC converter, IGBT, or the like can be used.

  Furthermore, in the present embodiment, the DC-DC converter 38 is controlled by the control device 42, but the present invention is not limited to this. For example, the DC-DC converter 38 is configured to perform step-up control of the DC-DC converter 38. May be configured to perform independently.

It is a schematic illustration of the engagement Ru supply system according to an embodiment of the present invention. It is explanatory drawing of the DC-DC converter which comprises the said power supply system. Control is a timing chart of your way. It is a flowchart explaining the said control method. 5 is a flowchart illustrating converter control in the flowchart of FIG. 4. It is an energy and current / voltage characteristic diagram of a normal battery and an abnormal battery. It is energy characteristic explanatory drawing of a battery. It is a timing chart explaining the control method of a comparative example. 1 is a configuration explanatory diagram of a fuel cell system of Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Power supply system 22 ... Fuel cell 24 ... Inverter 26 ... Motor 30 ... High voltage electrical storage device 32 ... Contactor 34 ... Downverter 36 ... Low voltage electrical storage device 38 ... DC-DC converter 40 ... Solenoid 42 ... Control device 44 ... Voltmeter 50 ... Coil 56 ... Control circuit 59 ... Capacitor

Claims (4)

A power generator,
A first power storage device that stores power generated by the power generation device;
A second power storage device that stores power having a lower voltage than the first power storage device;
A downverter that is provided between the first power storage device and the second power storage device, and that steps down the power from the first power storage device and supplies it to the second power storage device;
Provided between the first power storage device and the downverter, the first power storage device and the second power storage device can be electrically disconnected and switched from the second power storage device when the system is started. A switching device in which power is applied to the unit;
A converter provided between the second power storage device and the switching drive unit;
With power applied from the second power storage device, when lower than the voltage set voltage of the second power storage device to the system startup, and a control device for step-up control of the converter,
Equipped with a,
Power system driving voltage of the switching drive unit is characterized that you have been set to a voltage higher than the reset voltage of the control device. The power supply system according to claim 1, wherein the switching drive unit includes a solenoid,
Power supply system, wherein a driving voltage of the solenoid is set to a voltage higher than the previous cut set voltage.   3. The power supply system according to claim 1, wherein the control device outputs a boost command for the converter when a system activation signal is input.   4. The power supply system according to claim 1, wherein the control device stops boosting control of the converter when detecting that the switching device is in a conductive state. 5. system.

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