JP7618474B2 - Three-phase power conversion system for electric railways - Google Patents

Description

An embodiment of the present invention relates to a three-phase power conversion system for electric railways.

Three-phase power conversion systems for electric railways are known that are operated in conjunction with a three-phase railway power source such as a rotating machine. The three-phase power conversion system for electric railways supplies three-phase AC power to a feeding substation together with the three-phase railway power source. The feeding substation converts the three-phase AC power supplied from the three-phase railway power source and the three-phase power conversion system for electric railways into multiple single-phase AC powers, and supplies the multiple single-phase AC powers to multiple feeding circuits (railway loads). This allows power to be supplied to trains, enabling them to run.

The three-phase power conversion system for electric railways has multiple semiconductor switching elements. By switching the multiple semiconductor switching elements, the three-phase power conversion system for electric railways converts three-phase AC power supplied from a power system such as a power company into three-phase AC power compatible with the feeding circuit, and supplies the converted three-phase AC power to a feeding substation.

In these three-phase power conversion systems for electric railways, there is a possibility that a large transient current may flow through the system due to a short circuit in the feeding circuit or a ground fault. Three-phase railway power sources such as rotating machines have a certain supply capacity for transient large currents and can continue to operate. On the other hand, three-phase power conversion systems for electric railways, which are made up of multiple semiconductor switching elements, have difficulty bearing transient large currents. For this reason, three-phase power conversion systems for electric railways stop operating when a transient large current occurs to prevent damage to the multiple semiconductor switching elements.

However, if the operation of a three-phase electric railway power conversion system is stopped in response to the occurrence of a transient large current, the output of the three-phase electric railway power conversion system will also be stopped for unhealthy feeding circuits other than the feeding circuit where a short circuit or earth fault has occurred, among the multiple feeding circuits that supply single-phase AC power from the feeding substation. As a result, the power supply to the unhealthy feeding circuit will be solely from the three-phase railway power source, which may result in the loss of the stability of the feeding voltage required for the electric railway feeding system.

It has also been proposed that when a transient large current occurs, the output voltage of the three-phase electric railway power conversion system can be reduced to relatively reduce the output current and keep it within the tolerance of the three-phase electric railway power conversion system. However, this method is a control that can be applied when the three-phase electric railway power conversion system is operating independently. When the three-phase electric railway power conversion system is operated in connection with a three-phase railway power source, the voltage of the three-phase AC power is maintained by the output of the three-phase railway power source, making it difficult to reduce the output current of the three-phase electric railway power conversion system.

For this reason, it is desirable for three-phase power conversion systems for electric railways to be able to adequately protect the system while minimizing the impact on unhealthy power circuits when a transient large current occurs, even when the system is operated in conjunction with a three-phase railway power source.

JP 2014-80132 A JP 2017-175797 A

An embodiment of the present invention provides a three-phase power conversion system for electric railways that can adequately protect the system while suppressing the impact on an unhealthy power supply circuit when a transient large current occurs, even when the system is operated in conjunction with a three-phase railway power source.

According to an embodiment of the present invention, a three-phase power conversion system for electric railways is used in a feeding system including a feeding substation that converts three-phase AC power into multiple single-phase AC powers and supplies the multiple single-phase AC powers to multiple feeding circuits, and a three-phase railway power source that converts three-phase AC power into another three-phase AC power and supplies the converted three-phase AC power to the feeding substation, and is operated in conjunction with the three-phase railway power source, the three-phase power conversion system comprising: a converter that converts three-phase AC power into DC power; an inverter that converts the DC power output from the converter into another three-phase AC power different from the three-phase AC power supplied to the converter and supplies the converted three-phase AC power to the feeding substation; a current detector that detects a current value of the three-phase AC power supplied to the feeding substation or a current value of each of the multiple single-phase AC powers supplied to the multiple feeding circuits; and a current detector that detects a current value of the multiple single-phase AC powers supplied to the multiple feeding circuits based on the current value detected by the current detector. and a control device that controls the operation of converting the DC power to the three-phase AC power by the current detector. The control device determines whether the current flowing through each of the multiple power supply circuits is equal to or greater than a predetermined value based on the current value detected by the current detector. In normal operation, when it is determined that the current flowing through each of the multiple power supply circuits is less than the predetermined value, the control device controls the operation of the inverter so as to supply a predetermined active current and reactive current to each of the multiple power supply circuits by setting a predetermined current command value related to the output of the inverter. In a large current generation operation, when it is determined that the current flowing through any of the multiple power supply circuits is equal to or greater than the predetermined value, the control device controls the operation of the inverter so as to lower the current output from the inverter to the power supply circuit determined to be equal to or greater than the predetermined value by lowering the current command value compared to the normal operation.

A three-phase power conversion system for electric railways is provided that can adequately protect the system while minimizing the impact on unhealthy power circuits when a transient large current occurs, even when the system is operated in conjunction with a three-phase railway power source.

FIG. 1 is a block diagram illustrating a power feeding system according to an embodiment. 1 is a block diagram showing a schematic diagram of a three-phase power conversion system for an electric railway according to an embodiment; FIG. 2 is a block diagram illustrating a control device according to the embodiment.

Each embodiment will be described below with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing.
In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed descriptions thereof will be omitted as appropriate.

FIG. 1 is a block diagram that illustrates a power feeding system according to an embodiment.
As shown in FIG. 1 , the feeding system 2 includes a three-phase power conversion system 10 for an electric railway, a three-phase railway power source 12, a feeding substation 14, and a plurality of feeding circuits 21, 22.

The three-phase railway power supply 12 is, for example, a rotating machine formed by connecting a motor and a generator. The three-phase power conversion system for electric railways 10 is operated in connection with the three-phase railway power supply 12. The three-phase power conversion system for electric railways 10 and the three-phase railway power supply 12 are connected to a power system of a power company or the like, and convert the three-phase AC power supplied from the power system into another three-phase AC power corresponding to the feeding circuits 21, 22. Note that the power system to which the three-phase power conversion system for electric railways 10 is connected may be the same as the power system to which the three-phase railway power supply 12 is connected, or may be different.

The three-phase power conversion system 10 for electric railways and the three-phase railway power supply 12 are used, for example, as frequency conversion devices. The three-phase power conversion system 10 for electric railways and the three-phase railway power supply 12 convert, for example, 50 Hz three-phase AC power in the eastern region of Japan to 60 Hz three-phase AC power in the western region of Japan. However, the three-phase power conversion system 10 for electric railways and the three-phase railway power supply 12 are not limited to frequency conversion devices. The power conversion by the three-phase power conversion system 10 for electric railways and the three-phase railway power supply 12 is not limited to frequency conversion, and may also be conversion of the magnitude of voltage or current. The power conversion operation by the three-phase power conversion system 10 for electric railways and the three-phase railway power supply 12 may be any operation that converts three-phase AC power to another three-phase AC power.

The three-phase power conversion system 10 for electric railways and the three-phase railway power source 12 supply the converted three-phase AC power to the power supply substation 14.

The feeding substation 14 converts the three-phase AC power supplied from the electric railway three-phase power conversion system 10 and the three-phase railway power source 12 into multiple single-phase AC powers, and supplies the multiple single-phase AC powers to multiple feeding circuits 21, 22.

The feeding substation 14, for example, converts the three-phase AC power supplied from the electric railway three-phase power conversion system 10 and the three-phase railway power source 12 into two sets of single-phase AC power, supplies one of the two sets of single-phase AC power to the feeding circuit 21, and supplies the other of the two sets of single-phase AC power to the feeding circuit 22. In this way, the feeding substation 14 is connected to, for example, two feeding circuits 21, 22, and supplies single-phase AC power to each of the two feeding circuits 21, 22.

For example, a Scott connection transformer, a modified Woodbridge connection transformer, or a roof delta connection transformer may be used for the feeding substation 14. However, the number of feeding circuits connected to the feeding substation 14 is not limited to two, and may be three or more. The feeding substation 14 may be configured to convert three-phase AC power into three or more sets of single-phase AC power. In the following, the number of feeding circuits is two, and the feeding substation 14 is described as converting three-phase AC power into two sets of single-phase AC power. In the following, the feeding circuit 21 is described as the first feeding circuit 21, and the feeding circuit 22 is described as the second feeding circuit 22.

The first power supply circuit 21 and the second power supply circuit 22 supply power to the electric trains 23 and 24. As a result, the electric trains 23 and 24 can be supplied with power by the three-phase AC power supply from the electric railway three-phase power conversion system 10 and the three-phase railway power source 12, allowing the electric trains 23 and 24 to run.

The first feeding circuit 21 and the second feeding circuit 22 are each connected to the feeding substation 14 via a circuit breaker (not shown). In other words, the feeding system 2 further includes a plurality of circuit breakers provided between the feeding substation 14 and the first feeding circuit 21, and between the feeding substation 14 and the second feeding circuit 22. When an accident such as a short circuit or a ground fault occurs in the first feeding circuit 21 or the second feeding circuit 22, the feeding system 2 opens the circuit breaker corresponding to the feeding circuit in which the accident occurred.

By opening only the circuit breaker corresponding to the power supply circuit in which the accident occurred, the power supply system 2 prevents the continued supply of power to the power supply circuit in which the accident occurred, while continuing to supply power to the power supply circuit that is not healthy. As a result, even if an accident occurs in either the first power supply circuit 21 or the second power supply circuit 22, it is only necessary to stop the operation of trains on the power supply circuit in which the accident occurred, and train operation can continue on the other power supply circuit that is not healthy.

FIG. 2 is a block diagram that illustrates a three-phase power conversion system for electric railways according to an embodiment.
As shown in FIG. 2, the three-phase power conversion system 10 for an electric railway has a receiving transformer 40, a converter transformer 42, a converter 44, a DC capacitor 46, an inverter 48, an inverter transformer 50, a transmission transformer 52, a current detector 54, and a control device 56.

The primary side of the power receiving transformer 40 is connected to the power system 30. The secondary side of the power receiving transformer 40 is connected to the primary side of the converter transformer 42. The secondary side of the converter transformer 42 is connected to the converter 44. The power receiving transformer 40 and the converter transformer 42 transform the three-phase AC power supplied from the power system 30 into three-phase AC power corresponding to the converter 44.

The power system 30 is, for example, a power system of a power company. The power system 30 may be, for example, a power system that supplies three-phase AC power supplied from a private generator or the like to the three-phase power conversion system 10 for an electric railway. The power supply system 2 may further include, for example, a generator that outputs three-phase AC power, and a power system 30 that supplies the three-phase AC power of the generator to the three-phase power conversion system 10 for an electric railway.

In this example, two transformers, a power receiving transformer 40 and a converter transformer 42, are provided between the power system 30 and the converter 44. The number of transformers provided between the power system 30 and the converter 44 is not limited to two, and may be one, or three or more.

The converter 44 converts the three-phase AC power supplied from the converter transformer 42 into DC power. The converter 44 is, for example, a three-phase bridge rectifier circuit having multiple rectifier elements connected in a three-phase bridge. However, the configuration of the converter 44 is not limited to this, and any configuration capable of converting three-phase AC power into DC power may be used.

The DC capacitor 46 is provided between the converter 44 and the inverter 48. The DC capacitor 46 suppresses fluctuations in the voltage of the DC power output from the converter 44.

The inverter 48 converts the DC power output from the converter 44 into three-phase AC power. The inverter 48 converts the three-phase AC power supplied to the converter 44 into another three-phase AC power different from the three-phase AC power supplied to the converter 44. For example, when the three-phase power conversion system 10 for electric railways is a frequency conversion device, the inverter 48 converts the three-phase AC power supplied to the converter 44 into another three-phase AC power having a different frequency. For example, the converter 44 converts the supplied 50 Hz three-phase AC power into DC power, and the inverter 48 converts the DC power into 60 Hz three-phase AC power.

However, as described above, the three-phase power conversion system 10 for electric railways is not limited to a frequency conversion device. The inverter 48 may, for example, convert the three-phase AC power supplied to the converter 44 into another three-phase AC power having a different voltage and current magnitude.

The inverter 48 has multiple semiconductor switching elements (not shown) and converts DC power into three-phase AC power by switching the multiple semiconductor switching elements. The inverter 48 has multiple semiconductor switching elements connected in a three-phase bridge, for example. However, the configuration of the inverter 48 is not limited to the above, and may be any configuration that can convert DC power into three-phase AC power by switching the multiple semiconductor switching elements.

The primary side of the inverter transformer 50 is connected to the inverter 48. The secondary side of the inverter transformer 50 is connected to the primary side of the power transmission transformer 52. The secondary side of the power transmission transformer 52 is connected to the power feeding substation 14 via the power system 32 or the like. The inverter transformer 50 and the power transmission transformer 52 transform the three-phase AC power output from the inverter 48 into three-phase AC power corresponding to the power feeding substation 14.

As a result, the three-phase AC power output from the three-phase power conversion system for electric railways 10 is supplied to the feeding substation 14. In other words, the inverter 48 converts DC power to three-phase AC power, and supplies the converted three-phase AC power to the feeding substation 14 via the inverter transformer 50 and the transmission transformer 52. The three-phase railway power source 12 is connected, for example, to the power system 32. As a result, the three-phase AC power output from the three-phase power conversion system for electric railways 10 and the three-phase railway power source 12 is supplied to the feeding substation 14.

In this example, two transformers, an inverter transformer 50 and a transmission transformer 52, are provided between the power system 32 and the inverter 48. The number of transformers provided between the power system 32 and the inverter 48 is not limited to two, and may be one, or three or more.

The current detector 54 detects the current value of the three-phase AC power supplied to the feeding substation 14. The current detector 54 detects, for example, the current value of each phase of the three-phase AC power supplied to the feeding substation 14. The current detector 54 is provided, for example, between the inverter 48 and the primary side of the inverter transformer 50. In other words, the current detector 54 detects the current value of the three-phase AC power output from the inverter 48. The current detector 54 inputs the detected current value to the control device 56.

The location where the current detector 54 is provided is not limited to between the inverter 48 and the primary side of the inverter transformer 50. The current detector 54 may be provided, for example, between the secondary side of the inverter transformer 50 and the primary side of the transmission transformer 52, between the secondary side of the transmission transformer 52 and the power grid 32, or on the path of the power grid 32. The current value detected by the current detector 54 may be the current value of the three-phase AC power at any position between the inverter 48 and the feeder substation 14.

The control device 56 controls the operation of the inverter 48 to convert DC power to three-phase AC power. The control device 56 controls the operation of the inverter 48 based on the current value detected by the current detector 54.

The control device 56 may further control the operation of the converter 44 as necessary. For example, as described above, when the converter 44 is a three-phase bridge rectifier circuit, the control device 56 does not need to control the operation of the converter 44. For example, when the converter 44 is configured using multiple semiconductor switching elements, the control device 56 controls the power conversion operation of the converter 44. However, the control device that controls the operation of the converter 44 may be a device separate from the control device 56 that controls the operation of the inverter 48.

During normal operation when the first power supply circuit 21 and the second power supply circuit 22 are healthy, the control device 56 controls the operation of the inverter 48 so as to supply a predetermined active current and reactive current to each of the first power supply circuit 21 and the second power supply circuit 22.

As described above, in the power feeding system 2, due to the influence of fallen trees, etc., accidents such as short circuits and ground faults may occur in the first power feeding circuit 21 and the second power feeding circuit 22. When the power feeding system 2 detects an accident in the first power feeding circuit 21 and the second power feeding circuit 22, it opens the circuit breaker corresponding to the power feeding circuit in which the accident occurred and disconnects the power feeding circuit in which the accident occurred from the power feeding substation 14, thereby stopping the supply of power to the power feeding circuit in which the accident occurred. On the other hand, it takes, for example, about 150 ms for the power feeding system 2 to detect an accident in the first power feeding circuit 21 and the second power feeding circuit 22 and disconnect the power feeding circuit in which the accident occurred. For this reason, there is a possibility that a transient large current will flow in the electric railway three-phase power conversion system 10 and the three-phase railway power source 12 from the occurrence of the accident to the disconnection of the power feeding circuit by the power feeding system 2.

The three-phase railway power source 12, which is based on a rotating machine or the like, has a certain supply capacity for transient large currents, so it can continue to operate even in the event of an accident. On the other hand, the three-phase power conversion system 10 for electric railways, which has an inverter 48 consisting of multiple semiconductor switching elements, has difficulty in bearing transient large currents.

Therefore, the control device 56 determines whether the current flowing through the first feeder circuit 21 and the second feeder circuit 22 is equal to or greater than a predetermined value based on the current value detected by the current detector 54, and performs a protective operation to protect the inverter 48 in response to determining that the current through at least one of the first feeder circuit 21 and the second feeder circuit 22 is equal to or greater than the predetermined value. More specifically, the control device 56 determines whether the current flowing through the first feeder circuit 21 and the second feeder circuit 22 is equal to or greater than a predetermined value based on the instantaneous current value detected by the current detector 54. The control device 56 may, for example, determine whether at least one of the active current and the reactive current flowing through the first feeder circuit 21 and the second feeder circuit 22 is equal to or greater than a predetermined value.

When the control device 56 determines that the current flowing through the first power supply circuit 21 and the second power supply circuit 22 is less than a predetermined value under normal circumstances, it sets a predetermined current command value for the inverter 48, thereby controlling the operation of the inverter 48 to supply a predetermined active current and reactive current to each of the first power supply circuit 21 and the second power supply circuit 22.

When a large current occurs and the control device 56 determines that the current flowing through one of the first power supply circuit 21 and the second power supply circuit 22 is equal to or greater than a predetermined value, the control device 56 controls the operation of the inverter 48 so that the current output from the inverter 48 to one of the first power supply circuit 21 and the second power supply circuit 22 is reduced by lowering the current command value for one of the first power supply circuit 21 and the second power supply circuit 22 compared to normal times.

In addition, at this time, the control device 56 sets the current command value for the other of the first power supply circuit 21 and the second power supply circuit 22 to the same value as in normal times. In other words, when the control device 56 determines that the current flowing through one of the first power supply circuit 21 and the second power supply circuit 22 is equal to or greater than a predetermined value, it sets only the current command value for one of the first power supply circuit 21 and the second power supply circuit 22 to a value lower than in normal times.

This allows the inverter 48 to be controlled so that the current output to one of the first and second power supply circuits 21 and 22 where an accident has occurred is reduced while continuing to supply power to the other of the first and second power supply circuits 21 and 22 which is healthy and has not experienced an accident, thereby protecting the inverter 48 from transient large currents.

When the control device 56 determines that the current flowing through both the first power supply circuit 21 and the second power supply circuit 22 is equal to or greater than a predetermined value, it, for example, sets the current command value for both the first power supply circuit 21 and the second power supply circuit 22 lower than normal, or stops the operation of the inverter 48. However, in the power supply system 2, it is considered that the possibility of an accident occurring substantially simultaneously in both the first power supply circuit 21 and the second power supply circuit 22 is low.

FIG. 3 is a block diagram that illustrates a control device according to the embodiment.
As shown in FIG. 3, the control device 56 has a command value generating unit 60, a current value calculating unit 62, an operation status signal input unit 64, a first application determining unit 66a, a second application determining unit 66b, a first reduction rate calculating unit 68a, a second reduction rate calculating unit 68b, multipliers 70a to 70d, and a control signal generating unit 72.

Control information is input to the command value generating unit 60. Based on the input control information, the command value generating unit 60 generates a first active current command value for the first feeding circuit 21, a first reactive current command value for the first feeding circuit 21, a second active current command value for the second feeding circuit 22, and a second reactive current command value for the second feeding circuit 22.

In other words, the command value generating unit 60 sets the first active current command value, the first reactive current command value, the second active current command value, and the second reactive current command value as predetermined current command values related to the output of the inverter 48. In this way, the control device 56 regards the output of the inverter 48 as two sets of single-phase AC power and controls the operation of the inverter 48.

The command value generating unit 60 inputs the generated first active current command value to the multiplier 70a, the first reactive current command value to the multiplier 70b, the second active current command value to the multiplier 70c, and the second reactive current command value to the multiplier 70d.

The control information is input to the command value generating unit 60 from, for example, a higher-level controller. The control information represents, for example, the supply of power from the three-phase power conversion system for electric railways 10 to the first feeding circuit 21 and the second feeding circuit 22, and the stop of the power supply. The command value generating unit 60 generates each current command value when, for example, an instruction to supply power is received. The command value generating unit 60 stops generating each current command value or sets each current command value to an output stop state (for example, 0) when, for example, an instruction to stop the power supply is received.

The control information may include, for example, information indicating the magnitude of the current. The command value generating unit 60 may generate each current command value of the magnitude set by the control information. The control information may be, for example, a current command value of the three-phase AC power of the three-phase power conversion system for electric railways 10 (inverter 48). The command value generating unit 60 may generate each current command value of the single-phase AC power of the first power supply circuit 21 and the second power supply circuit 22 by performing a calculation to convert the current command value of the three-phase AC power.

The current command values may be input to the control device 56 from a higher-level controller or the like, rather than being generated within the control device 56. In this case, the input command values may be input directly to the multipliers 70a to 70d. Therefore, in this case, the command value generator 60 may be omitted.

The current value calculation unit 62 receives the current value of the three-phase AC power detected by the current detector 54. The current value calculation unit 62 performs a predetermined calculation on the current value of the input three-phase AC power to calculate the current values of the two sets of single-phase AC power of the first feeding circuit 21 and the second feeding circuit 22 from the current value of the three-phase AC power. The current value calculation unit 62, for example, calculates the instantaneous current value of each of the two sets of single-phase AC power. The current value calculation unit 62 may, for example, calculate the active current value and reactive current value of each of the two sets of single-phase AC power. The method of calculation of the current values of the two sets of single-phase AC power by the current value calculation unit 62 is determined according to the wiring method of the feeding substation 14.

After calculating the current values of the two sets of single-phase AC power, the current value calculation unit 62 determines whether the calculated current values of the two sets of single-phase AC power are equal to or greater than a predetermined value.

When the current value calculation unit 62 determines that the current value of the single-phase AC power of the first feeding circuit 21 is equal to or greater than a predetermined value, the current value calculation unit 62 inputs a first excessive current detection signal indicating that the current of the first feeding circuit 21 is excessive to the first application determination unit 66a. In other words, when the current value calculation unit 62 determines that the current value of the single-phase AC power of the first feeding circuit 21 is equal to or greater than a predetermined value, the current value calculation unit 62 switches the first excessive current detection signal from a non-detection state to a detection state. More specifically, when the current value calculation unit 62 determines that at least one of the active current value and the reactive current value of the single-phase AC power of the first feeding circuit 21 is equal to or greater than a predetermined value, the current value calculation unit 62 inputs the first excessive current detection signal to the first application determination unit 66a.

Similarly, when the current value calculation unit 62 determines that the current value of the single-phase AC power of the second power supply circuit 22 is equal to or greater than a predetermined value, it inputs a second current excess detection signal indicating that the current of the second power supply circuit 22 is excessive to the second application determination unit 66b.

The operation status signal input unit 64 inputs an operation status signal indicating whether or not the control device 56 will perform a protective operation of the inverter 48 to the first application determination unit 66a and the second application determination unit 66b. The operation status signal input unit 64 generates an operation status signal based on, for example, a control signal input from a higher-level controller or the internal control state of the control device 56, and inputs the generated operation status signal to the first application determination unit 66a and the second application determination unit 66b.

When the first excessive current detection signal is input from the current value calculation unit 62 while the operation state signal is in a state indicating that a protective operation for the inverter 48 is to be performed, the first application determination unit 66a inputs the first excessive current detection signal to the first reduction rate calculation unit 68a. On the other hand, when the first excessive current detection signal is input from the current value calculation unit 62 while the operation state signal is in a state indicating that a protective operation for the inverter 48 is not to be performed, the first application determination unit 66a does not input the first excessive current detection signal to the first reduction rate calculation unit 68a. This allows the control device 56 to perform a protective operation for the inverter 48 only when the operation state signal is in a state indicating that a protective operation for the inverter 48 is to be performed.

Similarly, when the second excessive current detection signal is input from the current value calculation unit 62 in a state where the operation status signal indicates that the inverter 48 is to be protected, the second application determination unit 66b inputs the second excessive current detection signal to the second reduction rate calculation unit 68b. When the second excessive current detection signal is input from the current value calculation unit 62 in a state where the operation status signal indicates that the inverter 48 is not to be protected, the second application determination unit 66b does not input the second excessive current detection signal to the second reduction rate calculation unit 68b.

The first reduction rate calculation unit 68a calculates the reduction rate of the first active current command value and the first reactive current command value based on the first current excess detection signal input from the first application determination unit 66a, and inputs the calculated reduction rate to the multipliers 70a and 70b.

The first reduction rate calculation unit 68a sets the reduction rate to 1 when the first excessive current detection signal is not input from the first application determination unit 66a. In other words, the first reduction rate calculation unit 68a sets the reduction rate to 1 when the first excessive current detection signal is in a non-detection state. Then, the first reduction rate calculation unit 68a sets the reduction rate to a predetermined value lower than 1 when the first excessive current detection signal is input from the first application determination unit 66a. In other words, the first reduction rate calculation unit 68a sets the reduction rate to a predetermined value lower than 1 when the first excessive current detection signal is in a detection state. In this case, the reduction rate is set to an arbitrary value lower than 1 that is necessary to protect the inverter 48 from a transient large current accompanying an accident in the first power supply circuit 21.

The first reduction rate calculation unit 68a may be configured to switch the reduction rate between two values, 1 and a predetermined value lower than 1, or may be configured to change the reduction rate according to the magnitude of the current value of the single-phase AC power of the first feeding circuit 21 that is determined to be equal to or greater than a predetermined value by the current value calculation unit 62. The first reduction rate calculation unit 68a may be configured to reduce the reduction rate as the current value of the single-phase AC power of the first feeding circuit 21 increases. For example, by including information representing the magnitude of the current value of the single-phase AC power of the first feeding circuit 21 in the first current excess detection signal, the reduction rate can be changed according to the magnitude of the current value of the single-phase AC power of the first feeding circuit 21, as described above.

The second reduction rate calculation unit 68b, like the first reduction rate calculation unit 68a, calculates the reduction rate of the second active current command value and the second reactive current command value based on the second current excess detection signal input from the second application determination unit 66b, and inputs the calculated reduction rate to the multipliers 70c and 70d.

The multiplier 70a multiplies the input first active current command value by the reduction rate, and inputs the multiplied first active current command value to the control signal generator 72.

The multiplier 70b multiplies the input first reactive current command value by the reduction rate, and inputs the multiplied first reactive current command value to the control signal generator 72.

The multiplier 70c multiplies the input second active current command value by the reduction rate, and inputs the multiplied second active current command value to the control signal generator 72.

The multiplier 70d multiplies the input second reactive current command value by the reduction rate, and inputs the multiplied second reactive current command value to the control signal generator 72.

The control signal generating unit 72 generates a control signal for controlling the operation of the inverter 48 based on each current command value input from the multipliers 70a to 70d so as to supply an active current corresponding to the first active current command value and a reactive current corresponding to the first reactive current command value to the first power supply circuit 21, and an active current corresponding to the second active current command value and a reactive current corresponding to the second reactive current command value to the second power supply circuit 22, and inputs the generated control signal to the inverter 48.

In addition, the control signal generating unit 72 receives, for example, information on the phase of the three-phase AC power supplied from the three-phase railway power source 12 to the feeding substation 14. Based on the input information, the control signal generating unit 72 generates a control signal for controlling the operation of the inverter 48 so that the phase of the three-phase AC power supplied from the inverter 48 to the feeding substation 14 is synchronized with the phase of the three-phase AC power supplied from the three-phase railway power source 12 to the feeding substation 14.

The control signal is, for example, a PWM signal for switching the on and off states of the multiple semiconductor switching elements of the inverter 48. The control signal generating unit 72 generates an active current command value and a reactive current command value, or an active voltage command value and a reactive voltage command value, of the three-phase AC power of the inverter 48, based on, for example, the active current command value and the reactive current command value of the two sets of single-phase AC power of the first power supply circuit 21 and the second power supply circuit 22. The control signal generating unit 72 then generates a control signal for switching the on and off states of the multiple semiconductor switching elements of the inverter 48, based on, for example, the active current command value and the reactive current command value, or the active voltage command value and the reactive voltage command value of the three-phase AC power of the inverter 48.

For example, the active current command value and reactive current command value of the three-phase AC power of the inverter 48, or the active voltage command value and reactive voltage command value of the three-phase AC power of the inverter 48, may be input to the inverter 48 as a control signal and converted to a PWM signal or the like within the inverter 48. The control signal is not limited to a PWM signal, and may be any signal that can control the operation of the inverter 48 so as to supply appropriate single-phase AC power to the first feeding circuit 21 and the second feeding circuit 22.

When the first power supply circuit 21 and the second power supply circuit 22 are in a healthy state, the reduction rate input from the first reduction rate calculation unit 68a and the second reduction rate calculation unit 68b to each multiplier 70a to 70d is 1, and each command value generated by the command value generation unit 60 is input directly to the control signal generation unit 72.

Therefore, during normal operation when the first power supply circuit 21 and the second power supply circuit 22 are in a healthy state, the operation of the inverter 48 is controlled so as to supply a predetermined active current and reactive current to each of the first power supply circuit 21 and the second power supply circuit 22 in accordance with each command value generated by the command value generating unit 60.

When an accident occurs in the first power supply circuit 21, a transient large current flows through the first power supply circuit 21, and the current value of the single-phase AC power of the first power supply circuit 21 becomes equal to or greater than a predetermined value, the current value calculation unit 62 determines that the current value of the single-phase AC power of the first power supply circuit 21 is equal to or greater than the predetermined value, and a first current overload detection signal is input from the current value calculation unit 62 to the first application determination unit 66a.

When the operation status signal indicates that a protective operation is to be performed on the inverter 48, and a first excessive current detection signal is input from the current value calculation unit 62 to the first application determination unit 66a, the first excessive current detection signal is input from the first application determination unit 66a to the first reduction rate calculation unit 68a.

When the first current excess detection signal is input from the first application determination unit 66a, the first reduction rate calculation unit 68a sets the reduction rate to a predetermined value lower than 1 and inputs it to the multipliers 70a and 70b.

As a result, when a large current occurs in which the current value of the single-phase AC power of the first power supply circuit 21 is equal to or greater than a predetermined value, the current command value for the first power supply circuit 21 becomes lower than normal, and the operation of the inverter 48 is controlled so that the current output from the inverter 48 to the first power supply circuit 21 becomes lower. This makes it possible to protect the inverter 48 from transient large currents.

In addition, at this time, if no accident has occurred in the second power supply circuit 22 and the current value of the single-phase AC power of the second power supply circuit 22 is less than a predetermined value, the reduction rate input from the second reduction rate calculation unit 68b to the multipliers 70c and 70d remains at 1. That is, the second active current command value and the second reactive current command value for the second power supply circuit 22 are the same as those in normal times. This allows the supply of power to a healthy second power supply circuit 22 in which no accident has occurred to continue. While continuing the supply of power to a healthy second power supply circuit 22 in which no accident has occurred, the inverter 48 is controlled so that the current output to the first power supply circuit 21 in which an accident has occurred is reduced, and the inverter 48 can be protected from a transient large current.

When the power feeding system 2 detects an accident in the first power feeding circuit 21, opens the circuit breaker corresponding to the first power feeding circuit 21 in which the accident occurred, and disconnects the first power feeding circuit 21 in which the accident occurred from the power feeding substation 14, the current value of the single-phase AC power of the first power feeding circuit 21 returns to less than the predetermined value. Therefore, after the power feeding system 2 disconnects the first power feeding circuit 21 from the power feeding substation 14, the reduction rate input from the first reduction rate calculation unit 68a to the multipliers 70a and 70b returns to 1, and the current command value for the first power feeding circuit 21 also returns to the normal state.

As in the case of the first feeding circuit 21, when the current value of the single-phase AC power of the second feeding circuit 22 is equal to or greater than a predetermined value, a second current excess detection signal is input from the second application determination unit 66b to the second reduction rate calculation unit 68b, and a reduction rate of a predetermined value lower than 1 is input from the second reduction rate calculation unit 68b to the multipliers 70c and 70d. As a result, when the current value of the single-phase AC power of the second feeding circuit 22 is equal to or greater than a predetermined value, the current command value for the second feeding circuit 22 is lower than normal, and the operation of the inverter 48 is controlled so that the current output from the inverter 48 to the second feeding circuit 22 is lower.

When no accident has occurred in the first power supply circuit 21, the inverter 48 is controlled to reduce the current output to the second power supply circuit 22 where an accident has occurred while continuing to supply power to the healthy first power supply circuit 21 where no accident has occurred, thereby protecting the inverter 48 from transient large currents.

As described above, in the three-phase power conversion system 10 for electric railways according to this embodiment, when a large current occurs and the control device 56 determines that the current flowing through one of the first feeder circuit 21 and the second feeder circuit 22 is equal to or greater than a predetermined value, the control device 56 controls the operation of the inverter 48 so that the current output from the inverter 48 to one of the first feeder circuit 21 and the second feeder circuit 22 is reduced by lowering the current command value for one of the first feeder circuit 21 and the second feeder circuit 22 compared to normal times.

This allows the inverter 48 to be controlled so that the current output to one of the first and second power supply circuits 21 and 22 in which an accident has occurred is reduced while continuing to supply power to the other of the first and second power supply circuits 21 and 22 in which an accident has occurred, thereby protecting the inverter 48 from a transient large current. Even when the three-phase power conversion system 10 for electric railways is operated in connection with the three-phase railway power source 12, when a transient large current occurs, the system can be appropriately protected while suppressing the impact on the unsound power supply circuit.

In addition, in the three-phase power conversion system 10 for electric railways according to this embodiment, the control device 56 treats the output of the inverter 48 as two sets of single-phase AC power and controls the operation of the inverter 48. This makes it possible to directly adjust the current command value of only the power supply circuit in which an accident has occurred. This makes it possible to realize control that more appropriately suppresses the impact on healthy power supply circuits.

However, the current command values set in the control device 56 do not necessarily have to be current command values for two sets of single-phase AC power. For example, current command values for the active current and reactive current of the three-phase AC power output from the inverter 48 may be set, and the current command values for the active current and reactive current of the three-phase AC power may be lowered so that the current output to the power supply circuit where the accident occurred is lowered. The current command value set in the control device 56 may be any current command value related to the output of the inverter 48.

In the above embodiment, the current detector 54 detects the current value of the three-phase AC power supplied to the feeding substation 14. Without being limited to this, the current detector 54 may be configured to detect, for example, each current value of the two sets of single-phase AC power after conversion in the feeding substation 14. This can eliminate the need for the control device 56 to calculate the current values of the two sets of single-phase AC power.

On the other hand, if the current detector 54 is configured to detect the current value of each of the two sets of single-phase AC power, the distance between the current detector 54 and the control device 56 may become large, and the layout configuration of the current detector 54 may become complicated. If the current detector 54 is configured to detect the current value of the three-phase AC power supplied to the feeding substation 14 as in the above embodiment, for example, the layout configuration of the current detector 54 may be simplified.

In the above embodiment, the number of feeding circuits connected to the feeding substation 14 is two. The number of feeding circuits connected to the feeding substation 14 is not limited to two, and may be three or more. When the number of feeding circuits is three or more, the control device 56 determines whether the current flowing through each of the multiple feeding circuits is equal to or greater than a predetermined value based on the current value detected by the current detector 54, and in normal times when it is determined that the current flowing through each of the multiple feeding circuits is less than the predetermined value, the control device 56 controls the operation of the inverter 48 so as to supply a predetermined active current and reactive current to each of the multiple feeding circuits by setting a predetermined current command value for the output of the inverter 48, and in high current generation times when it is determined that the current flowing through any of the multiple feeding circuits is equal to or greater than a predetermined value, the control device 56 controls the operation of the inverter 48 so as to lower the current command value compared to normal times so as to lower the current output from the inverter 48 to the feeding circuit determined to be equal to or greater than the predetermined value.

In the above embodiment, a rotating machine is given as an example of the three-phase railway power source 12. The three-phase railway power source 12 is not limited to a rotating machine, and may be any power source that has a certain supply capacity for a transient large current when an accident occurs in the power supply circuit and can continue operation even when an accident occurs.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

Description of the Related Art 2... Feeding system, 10... Three-phase power conversion system for electric railways, 12... Three-phase railway power source, 14... Feeding substation, 21, 22... Feeding circuit, 23, 24... Train, 30, 32... Power system, 40... Receiving transformer, 42... Converter transformer, 44... Converter, 46... DC capacitor, 48... Inverter, 50... Inverter transformer, 52... Transmission transformer, 54... Current detector, 56... Control device, 60... Command value generation unit, 62... Current value calculation unit, 64... Operational state signal input unit, 66a... First application determination unit, 66b... Second application determination unit, 68a... First reduction rate calculation unit, 68b... Second reduction rate calculation unit, 70a to 70d... Multipliers, 72... Control signal generation unit

Claims (4)

a feeding substation that converts three-phase AC power into a plurality of single-phase AC powers and supplies the plurality of single-phase AC powers to a plurality of feeding circuits;
a three-phase railway power source that converts three-phase AC power into another three-phase AC power and supplies the converted three-phase AC power to the feeding substation;
A three-phase power conversion system for electric railways used in a power feeding system including the above-mentioned three-phase railway power source,
A converter that converts three-phase AC power into DC power;
an inverter that converts DC power output from the converter into another three-phase AC power different from the three-phase AC power supplied to the converter, and supplies the converted three-phase AC power to the feeding substation;
a current detector that detects a current value of the three-phase AC power supplied to the feeding substation or a current value of each of the plurality of single-phase AC powers supplied to the plurality of feeding circuits;
a control device that controls an operation of converting the DC power into the three-phase AC power by the inverter based on the current value detected by the current detector;
Equipped with
The control device includes:
determining whether or not a current flowing through each of the plurality of feeding circuits is equal to or greater than a predetermined value based on the current value detected by the current detector;
In a normal state in which it is determined that the current flowing through each of the plurality of feeding circuits is less than the predetermined value, a predetermined current command value related to an output of the inverter is set, thereby controlling the operation of the inverter so as to supply a predetermined active current and a predetermined reactive current to each of the plurality of feeding circuits;
When a large current occurs and it is determined that the current flowing through any of the plurality of power supply circuits is equal to or greater than the predetermined value, the current command value is set lower than in the normal state, thereby controlling the operation of the inverter so that the current output from the inverter to the power supply circuit determined to be equal to or greater than the predetermined value is reduced. The number of the plurality of feeding circuits is two,
the feeding substation converts the three-phase AC power supplied from the three-phase railway power source and the inverter into two sets of single-phase AC power, and supplies the two sets of single-phase AC power to the two feeding circuits;
2. The three-phase power conversion system for electric railways according to claim 1, wherein the control device controls the operation of the inverter by regarding the outputs of the inverter as the two sets of single-phase AC power. The control device sets active and reactive current command values for each of the two power supply circuits, and when a large current occurs and it is determined that the current flowing through one of the two power supply circuits is equal to or greater than the predetermined value, the control device controls the operation of the inverter so that the current output from the inverter to one of the two power supply circuits is reduced by lowering the active and reactive current command values for one of the two power supply circuits compared to the normal state. The three-phase power conversion system for electric railways described in claim 2. The current detector detects a current value of the three-phase AC power supplied to the feeding substation,
4. The three-phase power conversion system for electric railways according to claim 2 or 3, wherein the control device calculates current values of the two sets of single-phase AC power of the two feeding circuits from the current values of the three-phase AC power by performing a predetermined calculation on the current values of the three-phase AC power detected by the current detector, and determines whether the current flowing in each of the two feeding circuits is equal to or greater than the predetermined value.

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