Circuit system for railroad vehicle

A circuit system for a railroad vehicle according to an embodiment includes a power conversion unit, a first converter, a second converter, a power storage unit, and a control unit. The power conversion unit converts power supplied from an overhead wire into power for driving a motor for running mounted on a railroad vehicle. The first converter converts power supplied from the overhead wire into DC power. The second converter converts power output from the first converter into power for driving a load mounted on the railroad vehicle. The power storage unit is electrically connected to an input side of the second converter. The control unit inputs regenerative power output from the power conversion unit to the first converter and inputs power output from the first converter to the power storage unit in a case where it is determined that the railroad vehicle is being regenerated.

TECHNICAL FIELD

Embodiments of the present invention relate to a circuit system for a railroad vehicle.

BACKGROUND ART

In recent years, there has become known a railroad vehicle that accumulates regenerative energy generated at the time of deceleration of the railroad vehicle in an electrical storage device, drives a motor for running using the power supplied from the electrical storage device, and runs by rotating wheels using a driving force of the motor for running. In addition, such a railroad vehicle can run by driving the motor for running using power supplied from an overhead wire. Here, since the energy used for the railroad vehicle is limited, it is preferable that the railroad vehicle be effectively utilized by improving the efficiency of use of energy used in the railroad vehicle.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

An object of the present invention is to provide a circuit system for a railroad vehicle capable of achieving effective utilization of power used in the railroad vehicle.

Solution to Problem

According to the present invention, a circuit system for a railroad vehicle according to an embodiment includes a power conversion unit, a first converter, a second converter, a power storage unit, and a control unit. The power conversion unit converts power supplied from an overhead wire into power for driving a motor for running mounted on a railroad vehicle. The first converter converts power supplied from the overhead wire into DC power. The second converter converts power output from the first converter into power for driving a load mounted on the railroad vehicle. The power storage unit is connected to an input side of the second converter. The control unit inputs regenerative power output from the power conversion unit to the first converter and inputs power output from the first converter to the power storage unit in a case where it is determined that the railroad vehicle is being regenerated.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a circuit system for a railroad vehicle according to an embodiment will be described with reference to the accompanying drawings.

First Embodiment

First, a first embodiment will be described.

FIG. 1is a configuration diagram showing a state where a railroad vehicle using a circuit system1for a railroad vehicle according to the first embodiment is in contact with an overhead wire P. The circuit system1for a railroad vehicle (hereinafter, referred to as the circuit system1) includes a breaker12, a charging circuit13, a filter reactor14, a discharging circuit16, a filter capacitor17, a power conversion unit20, a charging circuit30, a power storage unit40, a converter (first converter)50for a load, an inverter (second converter)51for a load, and a control unit60.

The railroad vehicle having the circuit system1mounted thereon receives power supplied from the overhead wire P coming into contact with a current collector2to drive a motor for running M and runs on a track not shown in the drawing. Further, in a case where power is not supplied from the overhead wire P, the motor for running M is driven by receiving power supplied from the power storage unit40of the circuit system1. In this manner, a railroad vehicle running by switching depending on a situation so as to use at least one of power supplied from the overhead wire P and power supplied from the power storage unit40may also be referred to as a hybrid railroad vehicle.

In addition, the railroad vehicle having the circuit system1mounted thereon receives power supplied from the overhead wire P or the power storage unit40to drive a load3. The load3is an auxiliary machine (for example, lighting equipment or heating and cooling equipment) mounted on a vehicle. Power supplied to the inverter51for a load driving the load3has a voltage lower than a voltage of power supplied to the power conversion unit20driving the motor for running M.

The circuit system1of the present application has a “normal mode” for running the railroad vehicle using power supplied from the overhead wire P and a “self-running mode (hereinafter, referred to as a self-running mode)” for running the railroad vehicle using power supplied from the power storage unit40. Here, whether the railroad vehicle is in a “normal mode” or a “self-running mode” is indicated by a control signal transmitted from a controller not shown in the drawing.

In a case where the railroad vehicle is run in a normal mode, power supplied from the overhead wire P is used as power for driving the motor for running M, and power having a voltage value (for example, approximately 1500 [V], and hereinafter referred to as a “high voltage”) which is higher than a voltage value of power supplied to the inverter51for a load driving the load3is supplied to the power conversion unit20driving the motor for running M.

In a case where the railroad vehicle is run in a self-running mode, power supplied from the power storage unit40is used as power for driving the motor for running M, and power having a voltage value (for example, approximately 750 [V], and hereinafter referred to as a “low voltage”) which is lower than a voltage value in the normal mode is supplied to the power conversion unit20.

In addition, the circuit system1has a regeneration function of regenerating power generated by the motor for running M, and the motor for running M is driven using high voltage power at the time of regeneration in a normal mode, whereby high voltage regenerative power is generated. Here, the wording “at the time of regeneration” indicates a case where power generation is performed using motive power input from axles of running wheels not shown in the drawing at the time of braking or acceleration of the railroad vehicle. In addition, whether the railroad vehicle is being “regenerated” is indicated by a control signal transmitted from a controller not shown in the drawing.

The motor for running M is driven using low voltage power at the time of regeneration in a self-running mode, whereby low voltage regenerative power is generated.

A fuse H is connected in series between the overhead wire P and the circuit system1. The fuse H is a protection circuit that protects the circuit system1. For example, in a case where a current of power supplied from the overhead wire P is a large current, a cutoff state where electrical connection between the overhead wire P and the circuit system1is cut off is set due to fusing inside the fuse H or the like in the circuit system1.

The breaker12is electrically connected in series between the fuse H and the charging circuit13. The breaker12sets an electrical connection state or a cutoff state between the fuse H and the charging circuit13. The breaker12is, for example, a high-speed breaker (HB).

The charging circuit13is a circuit, connected between the breaker12and the filter reactor14, which charges a filter capacitor17to be described later with high voltage or low voltage power. The charging circuit13includes, for example, a contactor LB electrically connected to a positive electrode wire LP, a contactor CHB electrically connected to the contactor LB in parallel, and a resistor CHRe.

The charging circuit13sets an electrical connection state or a cutoff state between the contactors LB and CHB under the control of the control unit60. In a case where charging of the filter capacitor17is started, first, the charging circuit13switches the contactor CHB to an electrical connection state. Thereafter, the charging circuit13switches the contactor LB to an electrical connection state and switches the contactor CHB from an electrical connection state to a cutoff state.

The filter capacitor17is charged by the contactor CHB being switched to an electrical connection state. In addition, the charging circuit13switches the contactor LB to an electrical connection state after the filter capacitor17is charged.

The filter reactor14is connected between the charging circuit13and the discharging circuit16and removes a high frequency component included in power input to the filter reactor14. For example, the filter reactor14removes a high frequency component included in power supplied from the overhead wire P and a high frequency component due to a control signal or the like included in power returned to the overhead wire P.

The discharging circuit16is a circuit that discharges the filter capacitor17connected between the positive electrode wire LP and the negative electrode wire LN between the filter reactor14and the filter capacitor17.

The discharging circuit16includes a discharging switch electrically connected to the filter capacitor17in parallel and a resistor connected to the discharging switch in series. The discharging circuit16sets the discharging switch to be in an electrical connection state or a cutoff state under the control of the control unit60. In a case where discharging of the filter capacitor17is started, the discharging circuit16sets the discharging switch to be in an electrical connection state. Thereafter, when discharging of the filter capacitor17is terminated, the discharging circuit16sets the discharging switch to be in a cutoff state.

The filter capacitor17smoothes power supplied to the power conversion unit20.

The power conversion unit20converts DC power supplied from the overhead wire P into AC power for driving the motor for running M mounted on the railroad vehicle. The power conversion unit20includes, for example, a switching element and switches the switching element to an electrical connection state or a cutoff state on the basis of a control signal received from the control unit60to convert DC power into AC power.

The charging circuit30has the same configuration as the charging circuit13, and thus description thereof will be omitted. However, the charging circuit13is different from the charging circuit30in that the charging circuit13charges the filter capacitor17using high voltage power supplied from the overhead wire P, whereas the charging circuit30charges the filter capacitor17using low voltage power supplied from the power storage unit40.

In the power storage unit40, a first terminal is connected to an input side of the inverter51for a load. The power storage unit40supplies power stored in the power storage unit40to the inverter51for a load on the basis of a control signal received from the control unit60.

Further, in the power storage unit40, a second terminal is connected to an input side of the discharging circuit16. The power storage unit40supplies power stored in the power storage unit40to the power conversion unit20on the basis of a control signal received from the control unit60.

The power storage unit40stores regenerative power supplied from the power conversion unit20at the time of regeneration on the basis of a control signal received from the control unit60.

Here, a voltage range of power stored in the power storage unit40is a low voltage. For this reason, in a case where regenerative power supplied from the power conversion unit20has a high voltage, the power of the high voltage regenerative needs to be converted into low voltage regenerative power and then stored in the power storage unit40.

In the circuit system1of the present embodiment, high voltage regenerative power is converted into low voltage regenerative power using a converter50for a load to be described later.

The converter50for a load converts input DC power into DC power having a desired current and voltage and outputs the converted DC power. The converter50for a load includes, for example, a switching element. The converter50for a load switches the switching element to an electrical connection state or a cutoff state on the basis of a control signal received from the control unit60to convert DC power supplied from the overhead wire P into DC power having a desired current and voltage.

The inverter51for a load converts power output from the converter50for a load into AC power for driving the load3.

The control unit60is a software functional unit which is realized by a processor such as a central processing unit (CPU) executing a program stored in a program memory. In addition, some or all of these functional units may be realized by hardware such as a large scale integration (LSI), an application specific integrated circuit (ASIC), or a field-programmable gate array (FPGA).

The control unit60controls the charging circuit13, the discharging circuit16, the power conversion unit20, the charging circuit30, the power storage unit40, the converter50for a load, and the inverter51for a load.

In addition, the control unit60receives a control signal transmitted from a controller provided in a steering wheel, not shown in the drawing, or the like of the railroad vehicle. The control signal transmitted from the controller includes information indicating whether a normal mode is set. In addition, the control signal transmitted from the controller includes information indicating whether power running is set. The control unit60determines whether a normal mode is set on the basis of a control signal received from the controller. In addition, the control unit60determines whether power running is set on the basis of a control signal received from the controller.

The control unit60inputs power supplied from the overhead wire P to the power conversion unit20through the overhead wire P, the fuse H, the breaker12, the charging circuit13, the filter reactor14, and the discharging circuit16as indicated by sign TRM at the time of power running in a normal mode. Since power supplied from the overhead wire P is high voltage power, the motor for running M is driven with a high voltage at the time of power running in a normal mode.

In addition, the control unit60inputs power supplied from the power storage unit40to the inverter51for a load from the power storage unit40as indicated by sign TRH at the time of power running in a normal mode.

The control unit60inputs regenerative power which is generated by the motor for running M and output from the power conversion unit20to the power storage unit40through the discharging circuit16, the charging circuit13, the breaker12, and the converter50for a load as indicated by sign TK at the time of regeneration in a normal mode. High voltage regenerative power output from the power conversion unit20is converted into low voltage regenerative power by being input to the converter50for a load and is output. That is, the high voltage regenerative power is stepped down by using the converter50for a load. Thereby, low voltage regenerative power is stored in the power storage unit40by utilizing high voltage power.

The control unit60inputs power supplied from the power storage unit40to the power conversion unit20through the charging circuit30and the discharging circuit16as indicated by sign GR at the time of power running in a self-running mode. Since power supplied from the power storage unit40is low voltage power, the motor for running M is driven with a low voltage at the time of power running in a self-running mode.

In addition, the control unit60inputs power supplied from the power storage unit40from the power storage unit40to the inverter51for a load as indicated by sign TRH in a self-running mode.

The control unit60inputs low voltage regenerative power generated by the motor for running M and output from the power conversion unit20to the power storage unit40through the discharging circuit16and the charging circuit30as indicated by sign GK at the time of regeneration in a self-running mode. Since the regenerative power is also low voltage power due to the motor for running M being driven with low voltage power, the low voltage regenerative power output from the power conversion unit20does not need to be converted into low voltage regenerative power for power storage and can be stored in the power storage unit40as it is.

In a case where the supply of power from the overhead wire P is started, the control unit60charges the filter capacitor17with power supplied from the overhead wire P. In this case, the control unit60charges the filter capacitor17using the charging circuit13.

Further, in a case where the supply of power from the power storage unit40is started, the control unit60discharges the filter capacitor17charged with power supplied from the overhead wire P. In addition, the control unit60charges the filter capacitor17with power supplied from the power storage unit40. In this case, the control unit60discharges the filter capacitor17using the discharging circuit16. In addition, the control unit60charges the filter capacitor17using the charging circuit30.

Here, operations of the circuit system1will be described usingFIG. 2.FIG. 2is a flowchart showing operations of the circuit system1.

The control unit60determines whether a normal mode is set on the basis of a control signal transmitted from the controller (step S11) Subsequently, the control unit60determines whether power running is set on the basis of a control signal transmitted from the controller (step S12).

The control unit60outputs DC power supplied from the overhead wire P to the power conversion unit20at the time of power running in a normal mode. The power conversion unit20converts the DC power supplied from the overhead wire P into AC power and supplies the AC power to the motor for running M (step S13). In this case, power supplied to the motor for running M is high voltage power.

In addition, the control unit60determines whether or not power supplied from the power storage unit40is output to the load3on the basis of information such as the amount of power stored in the power storage unit40(step S14). For example, the control unit60determines that power is output to the load3in a case where the amount of power stored is equal to or greater than a predetermined reference value, and the control unit60determines that power is not output to the load3in a case where the amount of power stored is less than the predetermined reference value. In a case where the control unit60determines that power supplied from the power storage unit40is output to the load3, the control unit outputs power supplied from the power storage unit40to the load3(step S15).

In a case where power running in a normal mode is not performed and regenerable power is obtained (for example, in a case where a regenerative brake is operating), the control unit60generates regenerative power in the power conversion unit20. In this case, the regenerative power generated in the power conversion unit20is high voltage power. The control unit60inputs the high voltage regenerative power generated by the power conversion unit20to the converter50for a load. The converter50for a load converts the high voltage regenerative power into low voltage regenerative power to step down the voltage and outputs the regenerative power having a stepped-down voltage. Thereby, low voltage regenerative power is stored in the power storage unit40(step S16).

In a case where a normal mode is not set (that is, in a case where a self-running mode is set), the control unit60outputs power supplied from the power storage unit40to the load3(step S17). Further, in a case where a self-running mode is set and power running is performed (step S18), the control unit60causes the power conversion unit20to convert power supplied from the power storage unit40into AC power and supplies the converted power to the motor for running M (step S19). In this case, the power supplied to the motor for running M is low voltage power.

In a case where power running in a self-running mode is not performed and regenerable power is obtained (for example, in a case where a regenerative brake is operating), the control unit60generates regenerative power in the power conversion unit20. In this case, regenerative power generated in the power conversion unit20is low voltage power. The control unit60inputs low voltage regenerative power generated by the power conversion unit20to the power storage unit40. Thereby, low voltage regenerative power output from the power conversion unit20is stored in the power storage unit40(step S20).

According to the above-described first embodiment, the circuit system1inputs high voltage regenerative power output from the power conversion unit20to the converter50for a load and inputs power output from the converter50for a load to the power storage unit40. Thereby, according to the circuit system1, high voltage regenerative power is stepped down by using the converter50for a load, and thus it is possible to store low voltage regenerative power in the power storage unit40and to achieve effective utilization of power used in the railroad vehicle. In addition, a voltage of power stored in the power storage unit40is stepped down by using the converter50for a load, and thus it is possible to save space without requiring use of a dedicated adjustment circuit (for example, a chopper circuit) which adjusts power to be stored in the power storage unit40.

In addition, the control unit60inputs power output from the power storage unit40to the inverter51for a load and converts the power into AC power for driving the load3. Thereby, according to the circuit system1, it is also possible to drive the load3with power output from the power storage unit40at the time of power running in a normal mode, to reduce the use of power supplied from the overhead wire P, and to achieve effective utilization of power used in the railroad vehicle.

In addition, the control unit60supplies power output from the power storage unit40to the power conversion unit20in a self-running mode. Thereby, according to the circuit system1, also in a system in which high voltage power is stepped down by using the converter50for a load and stored in the power storage unit40, it is possible to drive the motor for running M using power output from the power storage unit40and to achieve effective utilization of power used in the railroad vehicle.

In addition, the control unit60inputs regenerative power output from the power conversion unit20to the power storage unit40at the time of regeneration in a self-running mode. Thereby, according to the circuit system1, also in a system in which high voltage power is stepped down by using the converter50for a load and stored in the power storage unit40, it is possible to store regenerative power at the time of regeneration in a self-running mode in the power storage unit40and to achieve effective utilization of power used in the railroad vehicle.

Further, in a case where a normal mode is switched to a self-running mode, the control unit60controls the charging circuit30such that the filter capacitor17is charged with power output from the power storage unit40. Thereby, according to the circuit system1, also in a system in which high voltage power is stepped down by using the converter50for a load and stored in the power storage unit40, it is possible to supply power smoothed by the filter capacitor17in a self-running mode to the power conversion unit20and to achieve effective utilization of power used in the railroad vehicle.

Second Embodiment

Next, a second embodiment will be described.FIG. 3is a diagram illustrating the second embodiment. Components the same as the above-described components are denoted by the same reference numerals and signs, and description thereof will be omitted.

As shown inFIG. 3, a circuit system1according to the second embodiment further includes a chopper circuit32, a contactor36, and a filter capacitor33in addition to the circuit system1according to the first embodiment.

The chopper circuit32is connected between a power conversion unit20and a power storage unit40. The chopper circuit32adjusts a voltage of power output from the power storage unit40. The chopper circuit32steps down regenerative power output from the power conversion unit20from a high voltage to a low voltage and outputs the stepped-down power to the power storage unit40at the time of regeneration. In addition, the chopper circuit32steps up power output from the power storage unit40from a low voltage to a high voltage and supplies the stepped-up power to the power conversion unit20at the time of power running.

The chopper circuit32includes, for example, a switching element, a reactor, a rectifier, a capacitor, and the like. The chopper circuit32controls the turn-on and turn-off of the switching element of the chopper circuit32on the basis of, for example, a control signal (for example, a pulse width modulation (PWM) control signal) which is output from the control unit60. Thereby, the chopper circuit32steps down regenerative power output from the power conversion unit20and steps up power output from the power storage unit40.

The filter capacitor33is electrically connected to the chopper circuit32in parallel between the chopper circuit32and the discharging circuit16. The filter capacitor33smoothes power which is input to or output from the chopper circuit32.

The contactor36sets a cutoff state or a connected state between the chopper circuit32and the power conversion unit20under the control of the control unit60.

The control unit60controls the chopper circuit32and the contactor36. The control unit60inputs regenerative power output from the power conversion unit20to the power storage unit40through the discharging circuit16, the chopper circuit32, and the charging circuit30as indicated by sign TKa at the time of regeneration in a normal mode. High voltage regenerative power output from the power conversion unit20is stepped down by being input to the chopper circuit32and is output as low voltage regenerative power. Thereby, the low voltage regenerative power is stored in the power storage unit40.

In addition, the control unit60inputs power output from the power storage unit40to the chopper circuit32at the time of power running. Low voltage power output from the power storage unit40is stepped up by being input to the chopper circuit32and is output as high voltage power. High voltage power output from the chopper circuit32is supplied to the power conversion unit20.

The control unit60sets the contactor36to be in a cutoff state in order to protect the circuit system1, for example, in a case where an abnormal current is applied between the chopper circuit32and the power conversion unit20. Thereby, the control unit60prevents a defect from occurring in the circuit system1due to the application of an abnormal current in the circuit system1. In addition, the control unit60sets the contactor36to be in a cutoff state in a case where a normal mode is switched to a self-running mode in a circuit system1according to a third embodiment to be described later. In the circuit system1according to the second embodiment, the contactor36is set to be in a connected state in a normal case, except for an abnormal case such as a case where the above-described abnormal current is applied.

According to the above-described second embodiment, the circuit system1steps down regenerative power output from the power conversion unit20by the chopper circuit32and outputs the stepped-down power to the power storage unit40at the time of regeneration in a normal mode. Thereby, according to the circuit system1, also in a system in which high voltage power is stepped down by using a converter50for a load and stored in the power storage unit40, it is possible to step down regenerative power by using the chopper circuit32, to store the stepped-down power in the power storage unit40, and to achieve effective utilization of power used in the railroad vehicle.

In addition, the circuit system1steps up regenerative power output from the power storage unit40by the chopper circuit32and outputs the stepped-up power to the power conversion unit20at the time of power running. Thereby, according to the circuit system1, also in a system in which high voltage power is stepped down by using the converter50for a load and stored in the power storage unit40, it is possible to step up power output from the power storage unit40by using the chopper circuit32, to supply the stepped-up power to the power conversion unit20, and to achieve effective utilization of power used in the railroad vehicle.

Third Embodiment

Next, a third embodiment will be described.FIG. 4is a diagram illustrating the third embodiment. Components the same as the above-described components are denoted by the same reference numerals and signs, and description thereof will be omitted.

As shown inFIG. 4, a circuit system1according to the third embodiment does not include the charging circuit30of the circuit system1in the first embodiment. Further, in the circuit system1in the third embodiment, the chopper circuit32, the filter capacitor33, and the contactor36in the second embodiment are added to the circuit system1in the first embodiment. Further, in the circuit system1in the third embodiment, a connecting wire LH electrically connecting the chopper circuit32and an input side of the charging circuit13to each other and contactors34and35are added.

As described above, in a case where a normal mode is switched to a self-running mode, a control unit60discharges a filter capacitor17charged with power supplied from an overhead wire P and recharges the filter capacitor17with power supplied from the power storage unit40. Further, in the first embodiment and the second embodiment, the charging circuit13is used in a case where the filter capacitor17is charged with power supplied from the overhead wire P, and the charging circuit30is used in a case where the filter capacitor17is charged with power supplied from the power storage unit40.

In the third embodiment, the charging circuit13is used in both a case where the filter capacitor17is charged with power supplied from the overhead wire P and a case where the filter capacitor17is charged with power supplied from the power storage unit40.

The chopper circuit32, the filter capacitor33, and the contactor36are the same as those described in the second embodiment, and thus description thereof will be omitted.

The contactor34is electrically connected to the filter capacitor33in series and sets a cutoff state or a connected state between a positive-side terminal of the chopper circuit32and a positive-side terminal of the filter capacitor33on the basis of a control signal received from the control unit60. In a case where the contactor34is in a cutoff state, the filter capacitor33is not charged with power. In a case where the contactor34is in an electrical conduction state, the filter capacitor33can be charged with power.

The connecting wire LH electrically connects the chopper circuit32and an input side of the charging circuit13to each other.

The contactor35is provided in the connecting wire LH and sets a cutoff state or a connected state between the chopper circuit32and the input side of the charging circuit13on the basis of a control signal received from the control unit60.

The control unit60controls the contactors34,35, and36. In a case where a normal mode is switched to a self-running mode, the control unit60sets the contactor35to be in an electrical conduction state and sets the contactor36to be in a cutoff state. Thereby, as indicated by sign GJ, a voltage output from the power storage unit40through the chopper circuit32, the contactor35, the charging circuit13, the filter reactor14, and the discharging circuit16is input to the filter capacitor17. In this manner, the voltage output from the power storage unit40is input to the filter capacitor17, and thus it is possible to charge the filter capacitor17with power supplied from the power storage unit40.

Further, in a case where a normal mode is switched to a self-running mode, the control unit60sets the contactor34to be in a cutoff state. Thereby, the filter capacitor33is prevented from being charged with remaining power.

According to the above-described third embodiment, the control unit60controls the charging circuit13such that the filter capacitor17is charged. Thereby, also in a system in which high voltage power is stepped down by using the converter50for a load and stored in the power storage unit40, the circuit system1can effectively use the charging circuit13and achieve effective utilization of power used in the railroad vehicle. In addition, the charging circuit30is not required to be used, and thus it is possible to achieve space saving.

Further, in a case where the control unit60switches a normal mode to a self-running mode, the contactor34is opened. Thereby, also in a system in which high voltage power is stepped down by using the converter50for a load and stored in the power storage unit40, the circuit system1can prevent the filter capacitor33from being charged with remaining power and achieve effective utilization of power used in the railroad vehicle.

Modification Example of Embodiment

A modification example of an embodiment will be described with reference toFIG. 5.FIG. 5is a diagram illustrating a modification example of the first embodiment.FIG. 5is a configuration diagram showing a configuration of an insulated type converter50aused in the converter50for a load in the circuit system ofFIG. 1.

As shown inFIG. 5, the insulated type converter50aincludes an inverter500, a coil501, a coil502, and a rectifier503.

The inverter500converts DC power supplied from an overhead wire P into AC power. The inverter500includes, for example, a switching element and switches the switching element to an electrical connection state or a cutoff state to convert DC power into AC power.

The coil501is connected to the inverter500.

The coil502is connected to the rectifier503. The coil501and the coil502are electrically insulated from each other. The coil501is set to be a primary-side coil and the coil502is set to be a secondary-side coil, whereby an insulation transformer504is formed.

The rectifier503rectifies transformed AC power which is input through the coil502on the secondary side and converts the AC power into DC power. Thereby, power which is output from the rectifier503is transformed DC power.

According to the above-described modification example, the insulated type converter50ais used as the converter50for a load. Thereby, according to the circuit system1, the overhead wire P and the inverter51for a load can be electrically insulated from each other by the insulated type converter50a, and thus it is possible to prevent high voltage power supplied from the overhead wire P from being erroneously output to the inverter for a load in a high voltage state.

Meanwhile, a case where DC power is supplied from the overhead wire P has been described in at least one of the above-described embodiments, but the invention is not limited thereto. Power supplied from the overhead wire P may be AC power. In this case, for example, an AC/DC converter is used as the converter50for a load.

According to at least one of the above-described embodiments, the circuit system1for a railroad vehicle includes the power conversion unit20, the converter50for a load, the inverter51for a load, the power storage unit40, and the control unit60. Thereby, according to the circuit system1for a railroad vehicle, it is possible to achieve effective utilization of power used in the railroad vehicle.

Although some embodiments have been described above, those embodiments are described as examples, and do not intend to limit the scope of the invention. Those novel embodiments may be embodied in other various modes, and may be variously omitted, substituted, and modified without departing from the scope of the invention. Those embodiments and modification thereof are within the scope and the gist of the invention, and are within the scope of the invention described in the scope of claims and the equivalent thereof.

REFERENCE SIGNS LIST