JP2025032629A - On-board charging equipment - Google Patents

Abstract

To configure an on-vehicle charging device charging a DC power source connected to a traction rotary electric machine to be a drive power source of wheels with power from an external AC power source utilizing a coil and an inverter of the rotary electric machine loaded on a vehicle, while suppressing an increase in system cost.SOLUTION: An on-vehicle charging device comprises: a first circuit 1 including an AC/DC converter for converting power between AC power at the side of an external AC power source 4 and first DC power; and a second circuit 2 for generating second DC power with which a DC power source 3 is charged by attenuating a pulsation component from the first DC power. The second circuit 2 includes a half bridge circuit, a second circuit inductor, and a second circuit capacitor. The half bridge circuit is configured using an inverter 50, the second circuit inductor is configured using a plurality of coils 8, and a second circuit capacitor Co is connected between a neutral point 8N of the coils 8 and a negative electrode of the second circuit 2.SELECTED DRAWING: Figure 2

Description

The present invention relates to an on-board charging device.

JP2022-503713A discloses an onboard charger that charges a DC power source connected to a traction rotating electric machine that serves as a driving force source for the wheels of an electric vehicle or hybrid vehicle while the charger is mounted on the vehicle (the symbols in parentheses in the background art are those of the referenced document). Figure 3 of this document illustrates an onboard charger in which an external AC power source (310) is connected to the neutral point of a Y-connected three-phase coil, each of the three phase coils is connected to each AC side arm of an inverter (220), the input side terminal of a DC/DC converter is connected to the DC side terminal of the inverter (220), and the DC power source is connected to the output side terminal of the DC/DC converter. The three-phase coils and the inverter (220) form an AC/DC converter that converts a sine wave grid current from the external AC power source (310) into DC. By controlling the switching of the inverter (220), this AC-DC converter also functions as a power factor correction (PFC) circuit that improves the power factor of the DC power converted from the AC power. The current after AC-DC conversion generates ripples with a frequency twice the frequency (system frequency) of the external AC power source (310). The DC-DC converter reduces this ripple and generates a battery current for charging the DC power source.

Special Publication No. 2022-503713

Here, for example, in an on-board charging device for an electric vehicle or hybrid vehicle, a coil (stator coil) provided in the stator of a traction rotating electric machine mounted on the vehicle can be used as a three-phase coil. However, for example, a rotating electric machine mounted on a vehicle is designed to have a high power density, and the coil has a small inductance as an inductor of an AC-DC converter. As illustrated in FIG. 3 of the above document, when an AC-DC converter is formed by connecting an external AC power source to the neutral point of the coil, the peak value of the harmonic current of the system current of the external AC power source tends to be large during AC-DC conversion.

One method to suppress this is to increase the control frequency of the inverter that constitutes the AC-DC converter. Alternatively, to reduce ripples on the DC-DC converter side, it is possible to increase the control frequency of the DC-DC converter. However, when the control frequency is increased, it is necessary to shorten the control period (operating frequency) of the control device that controls the inverter and the DC-DC converter. In addition, switching at a high frequency due to a fast control period increases the loss in the switching elements of the inverter and the DC-DC converter, leading to a decrease in the efficiency of the vehicle-mounted charging device. In addition, it becomes necessary to use a microcomputer or the like capable of high-speed operation as the control device, which leads to an increase in the cost of the vehicle-mounted charging device. Alternatively, as another method, it is possible to add an inductor between the external AC power source and the neutral point of the coils of the multiple phases. However, in this case, the addition of the inductor also leads to an increase in the cost of the vehicle-mounted charging device.

In view of the above, it is desirable to configure an on-board charging device that uses the coil and inverter of a rotating electric machine mounted on a vehicle to charge a DC power source connected to a traction rotating electric machine that serves as a driving force source for the wheels, with power from an external AC power source, while suppressing increases in system costs.

In view of the above, the on-board charging device is a rotating electric machine that drives a drive object other than the traction rotating electric machine that serves as the driving force source for the wheels, and is mounted on a vehicle that includes an auxiliary rotating electric machine having a multi-phase coil connected to each other at a neutral point, a DC power source that supplies power to the auxiliary rotating electric machine and the traction rotating electric machine, and an inverter that converts power between the DC on the DC power source side and the multi-phase AC on the coil side of the auxiliary rotating electric machine, and is an on-board charging device that charges the DC power source with power supplied from an external AC power source, and includes an AC-DC converter that converts power between the AC power on the external AC power source side and a first DC power. and a second circuit that generates a second DC power for charging the DC power source by attenuating a pulsating component from the first DC power, the first circuit having an active rectifier with a power factor correction function, the second circuit having a half-bridge circuit arranged on the side of the AC-DC converter, a second circuit inductor arranged on the side of the DC power source, and a second circuit capacitor, the half-bridge circuit being configured using the inverter, the second circuit inductor being configured using a plurality of the coils, and the second circuit capacitor being connected between the neutral point of the coil and the negative pole of the second circuit.

According to this configuration, the first circuit, which requires an appropriate inductance for AC-DC conversion, is configured without using the drive circuit of the auxiliary rotating electric machine (the coil of the auxiliary rotating electric machine and the inverter that drives the auxiliary rotating electric machine). When a rotating electric machine coil such as the auxiliary rotating electric machine is used in the on-board charging device, it may be difficult to ensure the required performance due to the small inductance of the coil. However, according to this configuration, since an appropriate inductance can be set without using the coil of the auxiliary rotating electric machine, an AC-DC converter capable of AC-DC conversion can be configured while ensuring sufficient performance such as a power factor correction function. In addition, by using the drive circuit of the auxiliary rotating electric machine for the second circuit, which does not require high inductance, the cost of the on-board charging device can be reduced. Furthermore, since an appropriate inductance can be set in the first circuit, the need to control the active rectifier with a short control period (high control frequency) to compensate for the small inductance can be reduced, and the loss of the switching element that constitutes the active rectifier can also be easily reduced. Therefore, the system efficiency of the on-board charging device can also be easily increased.

In addition to the traction rotating electric machine, a vehicle may be equipped with an auxiliary rotating electric machine that serves as a driving force source for an air conditioner or an electric oil pump. In order to make such an auxiliary rotating electric machine output driving force, an increasing number of vehicles are configured so that the auxiliary rotating electric machine is supplied with power from a DC power source, just like the traction rotating electric machine. Compared to driving the wheels, the load of driving the air conditioner or the electric oil pump is small, and the coil of the auxiliary rotating electric machine and the inverter that drives the auxiliary rotating electric machine are often smaller than the coil and traction inverter of the traction rotating electric machine. In addition, such a small rotating electric machine circuit is often sufficient for the charging circuit. By configuring an on-board charging device using the circuit of the auxiliary rotating electric machine that drives a drive object other than the driving force source of the wheels, rather than the circuit of the traction rotating electric machine that is used to drive the wheels and is easily worn out, the burden on the vehicle on which the on-board charging device is installed can also be reduced.

In this way, with this configuration, it is possible to configure an on-board charging device that uses the coil and inverter of a rotating electric machine mounted on a vehicle to charge a DC power source connected to a traction rotating electric machine with power from an external AC power source while suppressing increases in system costs.

Further features and advantages of the on-board charging device will become apparent from the following description of exemplary, non-limiting embodiments, which are illustrated in the drawings.

Schematic circuit block diagram of a drive control system for a traction rotating electric machine and a rotating electric machine (an auxiliary rotating electric machine) A circuit block diagram showing a first example of an on-board charging device using a drive control system for a rotating electric machine. A circuit block diagram showing a second example of an on-board charging device using a drive control system for a rotating electric machine. A circuit block diagram showing a third example of an on-board charging device using a drive control system for a rotating electric machine. A circuit block diagram showing a fourth example of an on-board charging device using a drive control system for a rotating electric machine. A circuit block diagram showing a fifth example of an in-vehicle charging device using a drive control system for a rotating electric machine. A circuit block diagram showing a sixth example of an in-vehicle charging device using a drive control system for a rotating electric machine. A functional block diagram obtained by modifying the circuit block diagram shown in FIG. A circuit block diagram showing a seventh example of an on-board charging device using a drive control system for a rotating electric machine. A circuit block diagram showing an eighth example of an in-vehicle charging device using a drive control system for a rotating electric machine. A circuit block diagram showing a ninth example of an in-vehicle charging device using a drive control system for a rotating electric machine. A circuit block diagram showing a first comparative example of an on-board charging device using a drive control system for a rotating electric machine. A circuit block diagram showing a second comparative example of an on-board charging device using a drive control system for a rotating electric machine.

Below, an embodiment of the vehicle-mounted charging device will be described with reference to the drawings. The circuit block diagram of FIG. 1 shows a drive control system for the traction rotating electric machine 7M and the auxiliary rotating electric machine 8M (rotating electric machine). The traction rotating electric machine 7M is a rotating electric machine that serves as a driving force source for the wheels of the vehicle on which the vehicle-mounted charging device is mounted. In other words, the traction rotating electric machine 7M is a driving force source for the wheels of a hybrid vehicle, an electric vehicle, or the like. In addition to the traction rotating electric machine 7M, the vehicle may also have other driving force sources such as an internal combustion engine (not shown) as a driving force source for the wheels. The auxiliary rotating electric machine 8M is a rotating electric machine that drives a driving object other than the traction rotating electric machine 7M. The driving object is, for example, a compressor of an air conditioner mounted on the vehicle, or an electric oil pump.

The traction rotating electric machine 7M and the auxiliary rotating electric machine 8M are rotating electric machines equipped with multi-phase coils connected to each other at a neutral point. The traction rotating electric machine 7M is equipped with multi-phase traction coils 7 (U-phase coil 7u, V-phase coil 7v, W-phase coil 7w) connected to each other at a neutral point 7N. The auxiliary rotating electric machine 8M is equipped with multi-phase auxiliary coils 8 (U-phase coil 8u, V-phase coil 8v, W-phase coil 8w) connected to each other at a neutral point 8N. The traction rotating electric machine 7M is connected to a DC power source 3 via a traction inverter 5 that converts power between DC and multi-phase AC. Similarly, the auxiliary rotating electric machine 8M is connected to a DC power source 3 via an auxiliary inverter 50 (inverter) that converts power between DC and multi-phase AC. That is, the DC power source 3 is connected to the auxiliary rotating electric machine 8M and the traction rotating electric machine 7M to supply power to the auxiliary rotating electric machine 8M and the traction rotating electric machine 7M.

The circuit block diagram in FIG. 2 shows a first example of an on-board charging device 10 that utilizes a drive control system for an auxiliary rotating electric machine 8M. The on-board charging device 10 is a device that charges a DC power source 3 connected to the auxiliary rotating electric machine 8M and the traction rotating electric machine 7M while mounted on a vehicle. In other words, the on-board charging device 10 is a device that charges the DC power source 3 with power supplied from an external AC power source 4 (grid power source), and is a device that is so-called an onboard charger.

The vehicle-mounted charging device 10 of this embodiment is configured to share some parts with the auxiliary rotating electric machine 8M and its drive circuit. Specifically, the auxiliary inverter 50 and the auxiliary coil 8 of the auxiliary rotating electric machine 8M are shared. The DC link capacitor 6 is also shared. Note that all or at least some of the control devices (not shown) that control the switching elements and contactors (described later) provided in the vehicle-mounted charging device 10 may be shared with the control devices (accessory control device 88, traction control device 80, vehicle control device 90) that control the auxiliary rotating electric machine 8M and the traction rotating electric machine 7M.

As shown in FIG. 1, the vehicle is equipped with a traction control device 80 that controls the traction rotating electric machine 7M, and the traction control device 80 drives and controls the traction rotating electric machine 7M by performing current feedback control. The vehicle is also equipped with an auxiliary control device 88 (pump control device, air conditioner control device) that controls the auxiliary rotating electric machine 8M, and the auxiliary control device 88 drives and controls the auxiliary rotating electric machine 8M by performing current feedback control.

Both the traction rotating electric machine 7M and the auxiliary rotating electric machine 8M are interior permanent magnet type rotating electric machines (IPMSM: Interior Permanent Magnet Synchronous Motor) having a stator with multiple phases (N phases, where N is any natural number; in this embodiment, a three-phase form with N=3 is illustrated) of stator coils (traction coil 7, auxiliary coil 8) arranged in a stator core, and a rotor with a permanent magnet arranged in a rotor core. This configuration is well known, and in this embodiment, the stator core, stator, rotor core, rotor, permanent magnets, etc. are omitted from the illustration. In this embodiment, a Y-type (star type) form in which three-phase stator coils are short-circuited at neutral points (7N and 8N) is illustrated. However, the traction rotating electric machine 7M and the auxiliary rotating electric machine 8M may be, for example, provided with two sets of three-phase stator coils and driven by six-phase AC. At least the traction rotating electric machine 7M can function as both an electric motor and a generator. When the traction rotating electric machine 7M functions as an electric motor, the traction rotating electric machine 7M is in a powering state, and when the traction rotating electric machine 7M functions as a generator, the traction rotating electric machine 7M is in a regenerative state.

As shown in FIG. 1, the traction rotating electric machine 7M and the DC power source 3 are connected via a traction inverter 5. The auxiliary rotating electric machine 8M and the DC power source 3 are connected via an auxiliary inverter 50. The traction inverter 5 and the auxiliary inverter 50 convert power between multiple phases of AC and DC. In this embodiment, the inverter has a U-phase arm, a V-phase arm, and a W-phase arm as multiple phase arms (which may also be called legs). Each arm is formed by connecting an upper-stage switching element (5U, 50U) arranged on the positive side and a lower-stage switching element (5L, 50L) arranged on the negative side in series. The midpoint of each arm, i.e., the connection point between the upper-stage switching element and the lower-stage switching element, is connected to the respective coils (traction coil 7, auxiliary coil 8). Specifically, the midpoint of the U-phase arm is connected to the U-phase coil (7u, 8u), the midpoint of the V-phase arm is connected to the V-phase coil (7v, 8v), and the midpoint of the W-phase arm is connected to the W-phase coil (7w, 8w).

The DC side of the traction inverter 5 and the auxiliary inverter 50 is provided with a decoupling capacitor (DC link capacitor 6) that smoothes the voltage (DC link voltage) between the positive and negative poles. That is, the DC link capacitor 6 is connected in parallel to the DC power source 3.

The DC power source 3 is, for example, a rechargeable secondary battery (battery) such as a lithium ion battery, or an electric double layer capacitor. In the case where the traction rotating electric machine 7M is the driving force source of the vehicle as in this embodiment, the DC power source 3 is a high-voltage, large-capacity DC power source, and the rated power source voltage is, for example, 200 to 400 V. In many cases, the DC power source 3 is configured so that the electrical connection to the traction inverter 5 and the auxiliary inverter 50 can be disconnected by operating the main switch (ignition switch) of the vehicle. For example, the DC power source 3 is connected to the traction inverter 5 and the auxiliary inverter 50 via a main contactor 11 configured by a relay or the like. The relay may be a mechanical relay or a semiconductor relay (solid state relay). The same applies to other contactors below.

As shown in FIG. 1, the traction inverter 5 and the auxiliary inverter 50 are configured with a plurality of switching elements. FIG. 1 illustrates an example in which an IGBT (Insulated Gate Bipolar Transistor) is used as the switching element, but as illustrated in FIG. 2 and the like, a FET (Field Effect Transistor) may be used. In addition, in the examples shown in FIGS. 1 to 3, a freewheel diode is connected in parallel to each switching element with the forward direction being the direction from the negative electrode to the positive electrode (the direction from the lower side to the upper side). Of course, when a body diode is used or when reverse conduction is used in a transistor of a wide band gap semiconductor made of enhancement mode gallium nitride (E-GaN), such a freewheel diode may not be provided (for example, FIG. 4, etc.).

As shown in FIG. 1, the traction inverter 5 is controlled by the traction control device 80. The traction control device 80 is constructed with a logic circuit such as a microcomputer as its core component. For example, the traction control device 80 performs current feedback control based on the target torque (torque command) of the traction rotating electric machine 7M provided as a request signal from another control device such as a vehicle control device 90, which is one of the higher-level control devices, to drive the traction rotating electric machine 7M via the traction inverter 5. The operating voltage of logic circuit elements such as a microcomputer is generally 5 volts or less. In this embodiment, the control signal generated by the logic circuit element is transmitted to the traction inverter 5 via a drive circuit, which is not shown for simplicity. Alternatively, the traction control device 80 may be considered to include a drive circuit.

Similarly, the auxiliary inverter 50 is controlled by the auxiliary control device 88. The auxiliary control device 88 is also constructed with a logic circuit such as a microcomputer as its core component. The auxiliary control device 88 also performs current feedback control based on the target torque (torque command) and target rotation speed of the auxiliary rotating electric machine 8M provided as a request signal from another control device such as the vehicle control device 90, and drives the auxiliary rotating electric machine 8M via the auxiliary inverter 50. The control signal generated by the auxiliary control device 88 is also transmitted to the auxiliary inverter 50 via a drive circuit (not shown). As with the traction control device 80, the auxiliary control device 88 may be considered to include a drive circuit.

The actual current flowing through the traction coil 7 of each phase of the traction rotating electric machine 7M is detected by a current sensor (traction current sensor 81), and the traction control device 80 acquires the detection result. In addition, the magnetic pole position (electrical angle) of the rotor of the traction rotating electric machine 7M at each point in time and the rotation speed (angular velocity) of the rotor are detected by a traction rotation sensor 82 such as a resolver or an inductive position sensor, and the traction control device 80 acquires the detection result. The traction control device 80 executes current feedback control using the detection results of the traction current sensor 81 and the traction rotation sensor 82. The traction control device 80 is configured with various functional units for current feedback control, and each functional unit is realized by the cooperation of hardware such as a microcomputer and software (programs).

The actual current flowing through the auxiliary coil 8 of each phase of the auxiliary rotating electric machine 8M is detected by a current sensor (auxiliary current sensor 83), and the auxiliary control device 88 acquires the detection result. In addition, the magnetic pole position (electrical angle) of the rotor of the auxiliary rotating electric machine 8M at each point in time and the rotation speed (angular velocity) of the rotor are detected by an auxiliary rotation sensor 84 such as a resolver, an inductive position sensor, or a Hall element type rotation sensor, and the auxiliary control device 88 acquires the detection result. The auxiliary control device 88 executes current feedback control and Vf control using the detection results of the auxiliary current sensor 83 and the auxiliary rotation sensor 84. The auxiliary control device 88 is also configured with various functional units for current feedback control, and each functional unit is realized by cooperation between hardware such as a microcomputer and software (programs).

As described above, the traction rotating electric machine 7M connected to the DC power source 3 via the traction inverter 5 functions as an electric motor using the power supplied from the DC power source 3, and can also function as a generator to charge the DC power source 3. For example, in a hybrid vehicle, mechanical energy can be supplied to the traction rotating electric machine 7M using the power of an internal combustion engine or the like to cause the traction rotating electric machine 7M to generate electricity, but there are cases where the DC power source 3 cannot be sufficiently charged because there are few opportunities for power generation. In addition, in an electric vehicle equipped with only the traction rotating electric machine 7M as a driving force source, power generation is limited to mechanical energy from the wheels during inertial running, and the DC power source 3 cannot be sufficiently charged in many cases. In addition, even in a hybrid vehicle, it may be more energy efficient to supply power from an external source than to have the traction rotating electric machine 7M generate electricity. For this reason, it is preferable that the DC power source 3 be configured to be charged by an external power source when the DC power source 3 is installed in the vehicle.

When the DC power supply 3 is charged by an external power supply, it is preferable that an on-board charging device is installed in the vehicle. In many cases, the external power supply is AC because it receives power from a commercial power supply. For this reason, the on-board charging device is configured with a power conversion function from AC to DC. As a circuit for converting power from AC to DC, an AC-DC converter equipped with an inductor and a bridge circuit composed of switching elements is known. Although the conversion from AC to DC can be realized by a rectifier circuit using a rectifier element such as a diode, it is preferable that the power conversion is performed in a state where the power factor, which is determined by the phase of the AC voltage and current, is close to "1". For this reason, the AC-DC converter often includes a power factor correction circuit using a switching element so that the power factor can be improved.

Although an on-board charging device equipped with such a power conversion circuit tends to have a large circuit scale, there are fewer opportunities to charge the DC power source 3 compared to driving the wheels. Therefore, it is preferable that the on-board charging device has a small-scale configuration. When charging the DC power source 3 with an external power source, the vehicle is stopped (parked). Therefore, the traction inverter 5 made up of switching elements and the traction coil 7 of the traction rotating electric machine 7M having inductance are not used to drive the wheels when charging the DC power source 3 with an external power source. Therefore, it is conceivable to configure an on-board charging device using the traction inverter 5 and the traction coil 7.

Figure 12 shows an example of one conventional form of such an on-board charging device, and shows a first charging device 10X which is a comparative example of the on-board charging device 10 of this embodiment. The first charging device 10X is configured to share the traction coil 7 of the traction rotating electric machine 7M and the traction inverter 5 which drives and controls the traction rotating electric machine 7M. The first charging device 10X is configured to have a first circuit 1 equipped with an AC-DC converter and a second circuit 2 equipped with a DC-DC converter using a chopper circuit. The first circuit 1 is configured as a boost type AC-DC converter (AC/DC Boost Converter) equipped with an input inductor Li using the traction coil 7 and a full-bridge active rectifier using the traction inverter 5. The second circuit 2 is configured as a step-down type DC-DC converter (DC/DC Buck Converter) equipped with a step-down chopper.

As shown in FIG. 12, an external AC power supply 4 is connected to the neutral point 7N of the multi-phase traction coil 7. The full-bridge active rectifier also includes a full bridge 1c consisting of a first arm 1a (first leg) and a second arm 1b (second leg). The first arm 1a is formed by three arms (legs) of the traction inverter 5. The upper-stage switching elements 5U (see FIG. 1) of the traction inverter 5 are switched and controlled together, and the lower-stage switching elements 5L (see FIG. 1) are switched and controlled together, so that the traction inverter 5 with multiple phase arms can be regarded as a single-phase arm. In other words, the traction inverter 5 appears to have one arm.

The first circuit 1 and the second circuit 2 are selectively connected via a function switching contactor 12. When the traction coil 7 and the traction inverter 5 are used to drive the wheels, the first contact 12a of the function switching contactor is closed, and when the traction coil 7 and the traction inverter 5 are used to charge the DC power source 3, the second contact 12b of the function switching contactor is closed. In addition, the connection destination of the DC power source 3 is also switched by the main contactor 11. When the traction coil 7 and the traction inverter 5 are used to drive the wheels, the first contact 11a of the main contactor is closed, and when the traction coil 7 and the traction inverter 5 are used to charge the DC power source 3, the second contact 11b of the main contactor is closed.

However, rotating electric machines are designed to have a high power density, and the traction coil 7 may have a small inductance as the input inductor Li of the AC-DC converter. For this reason, the peak value of the pulsation of the harmonic current of the system current of the external AC power source 4 tends to become large during AC-DC conversion. In order to suppress this, it is preferable to increase the control frequency of the traction inverter 5 that constitutes the first circuit 1. Alternatively, the control frequency of the DC-DC converter may be increased to reduce the pulsation on the second circuit 2 side.

However, when the control frequency is increased, the control period (operating frequency) of the traction control device 80 that controls the traction inverter 5 and the DC-DC converter must also be shortened, which may increase the cost of the processor such as the microcomputer that is the core of the traction control device 80. In addition, switching at a high frequency associated with a fast control period increases losses in the switching elements of the traction inverter 5 and the chopper circuit of the second circuit 2, leading to a decrease in the efficiency of the first charging device 10X. For this reason, it is also preferable to add an additional inductor La between the external AC power source 4 and the neutral point 7N of the traction coil 7, as in the second charging device 10Y illustrated in FIG. 13.

As mentioned above, in addition to the traction rotating electric machine 7M, a vehicle may be equipped with an auxiliary rotating electric machine 8M that serves as a driving force source for auxiliary equipment such as an air conditioner and an electric oil pump. In a conventional vehicle that uses only an internal combustion engine as a driving force source for the wheels, the exhaust heat of the internal combustion engine can be used for the air conditioner, but in a hybrid vehicle or an electric vehicle, the same amount of exhaust heat as an internal combustion engine cannot be expected, and temperature control using a heat pump or the like is required, and the output required for the auxiliary rotating electric machine 8M tends to be large. Also, unlike an internal combustion engine that is constantly operating, such as idling, even when the vehicle is stopped (when the wheels are not rotating), the traction rotating electric machine 7M stops when the vehicle is stopped. A mechanical oil pump that draws in and discharges oil using the power of the internal combustion engine cannot supply oil for lubrication or cooling while the vehicle is stopped, and an electric oil pump is used, so the output required for the auxiliary rotating electric machine 8M tends to be large.

In order to output a large driving force to the auxiliary rotating electric machine 8M, an increasing number of vehicles are configured so that the auxiliary rotating electric machine 8M is supplied with power from a DC power source 3, just like the traction rotating electric machine 7M. Compared to driving the wheels, the load of driving an air conditioner or an electric oil pump is small, and the auxiliary coil 8 of the auxiliary rotating electric machine 8M and the auxiliary inverter 50 that drives the auxiliary rotating electric machine 8M are often smaller than the traction coil 7 and traction inverter 5 of the traction rotating electric machine 7M. In addition, the circuit of the auxiliary rotating electric machine 8M, which is small, is often sufficient for the charging circuit. As shown in FIG. 2, the load on the vehicle equipped with the on-board charging device 10 can be reduced by configuring the on-board charging device 10 using the circuit of the auxiliary rotating electric machine 8M that drives a drive object other than the driving force source of the wheels, rather than the circuit of the traction rotating electric machine 7M that is used to drive the wheels and is easily worn out.

The vehicle-mounted charging device 10 of the first example shown in FIG. 2 is equipped with a multi-phase auxiliary coil 8 connected to each other at a neutral point 8N, and is mounted on a vehicle equipped with an auxiliary rotating electric machine 8M that drives a drive object other than the traction rotating electric machine 7M that serves as a driving force source for the wheels, an auxiliary inverter 50 that converts power between DC and multi-phase AC, and a DC power source 3 that supplies power to the auxiliary rotating electric machine 8M and the traction rotating electric machine 7M, and charges the DC power source 3 with power supplied from an external AC power source 4. The vehicle-mounted charging device 10 is equipped with a first circuit 1 equipped with an AC-DC converter that converts power between the AC power on the side of the external AC power source 4 and the first DC power, and a second circuit 2 that attenuates the pulsating component from the first DC power to generate a second DC power that charges the DC power source 3.

The first circuit 1 is equipped with an active rectifier with a power factor correction function. Unlike the first charging device 10X, the first circuit 1 is configured without sharing a circuit with the traction rotating electric machine 7M, the auxiliary rotating electric machine 8M, the traction inverter 5, and the auxiliary inverter 50.

The second circuit 2 includes a half-bridge circuit arranged on the side of the AC-DC converter, a second circuit inductor arranged on the side of the DC power source 3, and a second circuit capacitor. In this embodiment, the second circuit 2 is a DC-DC converter equipped with a chopper circuit that converts power between a first DC power and a second DC power, the second circuit inductor is a reactor (which may also be called a choke coil) of the chopper circuit, and the second circuit capacitor is an output capacitor Co connected in parallel to the DC power source.

The half-bridge circuit is constructed using the auxiliary inverter 50, and the second circuit inductor (reactor) is constructed using multiple auxiliary coils 8. As described above, the upper stage switching elements 50U (see FIG. 1) of the auxiliary inverter 50 are collectively switched and the lower stage switching elements 50L (see FIG. 1) are collectively switched, so that the auxiliary inverter 50 having three-phase arms appears to be one arm and constitutes a half-bridge circuit. Similarly, the three-phase auxiliary coil 8 also appears to constitute one inductor. The second circuit capacitor is connected between the neutral point 8N of the auxiliary coil 8 and the negative pole of the second circuit 2. The second capacitor is connected in parallel to the DC power source 3 and functions as an output capacitor Co.

In the first example of the on-board charging device 10, the neutral point 8N and the positive electrode of the output capacitor Co are connected via a function switching contactor 12, and the positive electrode of the output capacitor Co and the positive electrode of the DC power supply 3 are connected via a main contactor 11. In addition, the external AC power supply 4 and the first circuit 1 are connected via a grid contactor 13 and an EMI filter FLT that reduces EMI (Electro Magnetic Interference) noise.

When the main contactor first contact 11a and the main contactor second contact 11b are closed, the function switching contactor 12 is open, and the grid contactor 13 is open, the traction inverter 5 and the auxiliary inverter 50 are used to pass AC current through the traction coil 7 and the auxiliary coil 8 to drive the traction rotating electric machine 7M and the auxiliary rotating electric machine 8M. When the main contactor first contact 11a is open and the main contactor second contact 11b is closed, the function switching contactor 12 is closed, and the grid contactor 13 is closed, the auxiliary inverter 50 and the auxiliary coil 8 are used as the on-board charging device 10.

Unlike the first charging device 10X and the second charging device 10Y, the in-vehicle charging device 10 of this embodiment is configured such that the first circuit, which requires an appropriate inductance for AC-DC conversion, does not use a driving circuit of a rotating electric machine (a coil of the rotating electric machine and an inverter that drives the rotating electric machine). As described above, when a coil of a rotating electric machine is used in the in-vehicle charging device 10, it may be difficult to ensure the required performance due to the small inductance of the coil. However, the in-vehicle charging device 10 of this embodiment can set an appropriate inductance without using a coil of a rotating electric machine in the first circuit 1, so that an AC-DC converter capable of AC-DC conversion can be configured while ensuring sufficient performance such as a power factor correction function. In addition, by using a driving circuit of the auxiliary rotating electric machine 8M in the second circuit 2, which does not require high inductance, the cost of the in-vehicle charging device 10 can be reduced. Furthermore, because it is possible to set an appropriate inductance in the first circuit 1, there is no need to control the active rectifier with a short control period (high control frequency), and the loss in the switching element 1S of the first circuit 1 that constitutes the active rectifier is also easily reduced. Therefore, it is also easy to increase the system efficiency of the vehicle-mounted charging device 10.

The main contactor 11 is not limited to the first example shown in FIG. 2, and may have a first main contactor contact 11a and a second main contactor contact 11b arranged as in the second example shown in FIG. 3. In the first example, the first main contactor contact 11a and the second main contactor contact 11b are both closed, but in the second example, the first main contactor contact 11a and the second main contactor contact 11b are selectively closed. In the first example, the output capacitor Co is connected in parallel to the DC power source 3 whether the auxiliary inverter 50 is used to drive the auxiliary rotating electric machine 8M or is used in the vehicle-mounted charging device 10. In the second example, when the auxiliary inverter 50 is used to drive the auxiliary rotating electric machine 8M, the output capacitor Co is opened, and only when the auxiliary inverter 50 is used in the vehicle-mounted charging device 10, the output capacitor Co is connected in parallel to the DC power source 3.

In the first and second examples described above with reference to Figures 2 and 3, the switching element 1S of the first circuit 1, the switching element 50S of the auxiliary inverter 50 used in the second circuit 2, and the switching element 5S of the traction inverter 5 are all MOSFETs. However, as in the third example shown in Figure 4, all of these switching elements may be junction FETs.

The switching element 1S constituting the active rectifier in the first circuit 1 and the switching element 50S of the auxiliary inverter 50 constituting the chopper circuit in the second circuit 2 are preferably composed of gallium nitride switching elements.

Gallium nitride switching elements have the following characteristics: low on-resistance, resulting in low conduction loss; high-speed switching, resulting in low switching loss; low parasitic capacitance, resulting in low loss; low power required to drive the circuit; small elements, which make it easy to reduce the space they occupy on the circuit board; and lower manufacturing costs than silicon semiconductors. Therefore, the vehicle-mounted charging device 10 can be constructed at low cost. On the other hand, due to the characteristic that the threshold value of the gate drive voltage is low, they are more vulnerable to noise than silicon semiconductors. However, when the DC power source 3 is charging, the vehicle is stopped, and the influence of external noise is relatively small. In addition, the reliability requirements for noise resistance are lower for the auxiliary inverter 50 used to drive the auxiliary rotating machine 8M, which is separate from the traction rotating machine 7M, than for the circuit (e.g., the traction inverter 5) that drives the traction rotating machine 7M. Therefore, by configuring the active rectifier and the auxiliary inverter 50 with gallium nitride switching elements, the vehicle-mounted system including the vehicle-mounted charging device 10 can be realized at lower cost.

That is, the switching elements (switching element 1S and switching element 50S) used in the vehicle-mounted charging device 10 and the switching element 5S of the traction inverter 5 may be different types of elements. As in the fourth example shown in FIG. 5, the switching elements (switching element 1S and switching element 50S) used in the vehicle-mounted charging device 10 may be junction type FETs, and the switching element 5S of the traction inverter 5 may be MOSFETs. Also, as in the fifth example shown in FIG. 6, the switching elements (switching element 1S and switching element 50S) used in the vehicle-mounted charging device 10 may be junction type FETs, and the switching element 5S of the traction inverter 5 may be IGBTs.

In the above, referring to Figures 2 to 6, an example has been given in which the second circuit 2 is a DC-DC converter equipped with a chopper circuit that converts power between a first DC power and a second DC power, the second circuit inductor is a reactor of the chopper circuit, and the second circuit capacitor is an output capacitor Co connected in parallel to the DC power source 3.

In the first circuit 1, the first DC power converted from the AC power by the AC-DC converter often retains pulsation of harmonic components of the AC power frequency. By providing the second circuit 2 with a DC-DC converter, the pulsation components can be suppressed, and the second DC power with reduced pulsation components compared to the first DC power can be supplied to the DC power source 3 to charge the DC power source 3.

As another configuration, as shown in the sixth example in FIG. 7, the vehicle-mounted charging device 10 may be an active decoupling circuit in which the second circuit 2 is connected to the DC side of the first circuit 1 and the DC side of the auxiliary inverter 50 without passing through any other passive components, and the second circuit capacitor may be an active filter capacitor Cs connected between the neutral point 8N of the auxiliary coil 8 and the negative pole of the second circuit 2 without being connected to the DC power source 3.

In the first circuit 1, the first DC power converted from the AC power by the AC-DC converter often retains pulsation of harmonic components of the AC power frequency. For this reason, in many cases, a decoupling capacitor (DC link capacitor 6 in Figures 2 to 6) is provided downstream of the first circuit 1 to smooth the pulsating components, and the second DC power with reduced pulsating components is often supplied to the DC power source via a DC-DC converter or the like. In the sixth example of the on-board charging device 10, the pulsating components can be reduced by connecting the second circuit 2 equipped with an active decoupling circuit to the first circuit 1 without going through such a decoupling capacitor, making it easy to keep the circuit size small.

The inventors' experiments and simulations have revealed that the DC link capacitor 6 of the first example requires approximately twice the capacity of the DC link capacitor 6 of the vehicle-mounted charging device 10 of the sixth example. Therefore, the vehicle-mounted charging device 10 of the sixth example is easier to miniaturize and reduce system costs than the vehicle-mounted charging device 10 of the first example.

The in-vehicle charging device 10 of the sixth example includes a main contactor 11 that electrically connects and disconnects the DC power source 3 and the DC side of the auxiliary inverter 50, a function switching contactor 12 that electrically connects and disconnects the neutral point 8N and the active filter capacitor Cs, and a grid contactor 13 that electrically connects and disconnects the first circuit 1 and the external AC power source 4. In the first example, the main contactor 11 has two contacts (main contactor first contact 11a and main contactor second contact 11b). Since a large current flows through both the main contactor first contact 11a and the main contactor second contact 11b, the component size of the main contactor 11 tends to be relatively large. In the in-vehicle charging device 10 of the sixth example, the main contactor 11 is configured to have only one contact. This prevents the main contactor 11 from becoming too large, and also prevents the on-board charging device 10 from becoming too large, making it easier to reduce system costs.

In the sixth example of the on-board charging device 10, the neutral point 8N and the positive electrode of the active filter capacitor Cs are connected via a function switching contactor 12. The positive electrode of the DC side of the auxiliary inverter 50 and the positive electrode of the DC power supply 3 are connected via a main contactor 11. In addition, the external AC power supply 4 and the first circuit 1 are connected via a grid contactor 13 and an EMI filter FLT.

When the main contactor 11 is closed, the function switching contactor 12 is open, and the grid contactor 13 is open, the traction inverter 5 and the auxiliary inverter 50 are used to pass AC current through the traction coil 7 and the auxiliary coil 8 to drive the traction rotating electric machine 7M and the auxiliary rotating electric machine 8M. When the main contactor 11 is closed, the function switching contactor 12 is closed, and the grid contactor 13 is closed, the auxiliary inverter 50 and the auxiliary coil 8 are used as the on-board charging device 10.

The circuit block diagram in FIG. 8 is a functional division of the circuit block diagram in FIG. 7 for ease of understanding. The first circuit 1 adjusts the power factor of the grid current Igrid supplied from the external AC power source 4 to a value close to "1" while boosting the voltage. However, the first DC power output from the first circuit 1 has a pulsation component caused by the AC frequency of the external AC power source 4 superimposed thereon. Specifically, the pulsation of the second harmonic component and the fourth harmonic component of the AC frequency of the external AC power source 4 is superimposed thereon. The second circuit 2, which functions as an active decoupling circuit, reduces the pulsation of such even-order harmonic components and supplies the second DC power with suppressed pulsation, preferably the second DC power with removed pulsation, to the DC power source 3 to charge the DC power source 3.

Here, if the AC voltage supplied from the external AC power source 4 is the "grid voltage Vgrid" and the AC current is the "grid current Igrid", the input power Pin supplied from the external AC power source 4 is expressed by the following formula (1). If it is assumed that the input power Pin is converted to the first DC power with a power factor of "1", the relationship between the input power Pin and the first DC power can be approximated by the following formula (2). Formula (2) indicates that the first DC power contains a DC component Pdc and an AC component Prpl.

Pin=Vgrid・Igrid...(1)
Pin≒Pdc+Prpl...(2)

The active decoupling circuit functions by passing a current corresponding to the AC component Prpl included in equation (2), i.e., the AC component Prpl included in the first DC power, through the active decoupling circuit so that the output power Pout to the DC power supply 3 is only the DC component Pdc included in equation (2) (equation (3)). The second circuit 2 as an active decoupling circuit operates to match the capacitor power Pcs, which is the power in the active filter capacitor Cs, with the AC component Prpl of the first DC power, as shown in the following equation (4).

Pout=Pdc...(3)
Prpl=Pcs...(4)

The capacitor power Pcs satisfies the relationship of the following equation (5) between the capacitor voltage Vcs and the capacitor current Ics, so the capacitor power Pcs can be controlled by appropriately controlling the capacitor current Ics.

Pcs=Vcs・Ics...(5)

As described above, the inductance of the auxiliary coil 8 of the auxiliary rotating electric machine 8M is small, so in the active decoupling circuit, an inductor (auxiliary coil 8) is used to pass current, not to store energy. Also, in the on-board charging device 10 of the sixth example, it is preferable to realize the decoupling action of the active decoupling circuit by making the capacitor current Ics a discontinuous current by pulse width modulation, rather than a so-called continuous current.

As described above, the auxiliary inverter 50 is configured with multiple arms in parallel, in which the upper-stage switching element 50U and the lower-stage switching element 50L are connected in series between the positive and negative poles of the DC, according to the number of phases of the multi-phase AC. In this embodiment, the auxiliary inverter 50 is configured with three arms. When the auxiliary inverter 50 functions as an active decoupling circuit, the multiple upper-stage switching elements 50U are simultaneously switched and the multiple lower-stage switching elements 50L are simultaneously switched. In other words, the auxiliary inverter 50 having multiple phase arms corresponding to the multi-phase AC can be used as an inverter (half-bridge circuit) having a single-phase arm. Since the current flows in a distributed manner in multiple arms, it is easy to suppress wear of the auxiliary inverter 50 even if the auxiliary inverter 50 is used as part of the in-vehicle charging device 10.

In the switching control, switching control signals (switching pulses) for the upper-stage switching element 50U and the lower-stage switching element 50L are generated based on a sinusoidal capacitor current command I ^* cs. The phase of the capacitor current command I ^* cs coincides with the phase of the grid voltage Vgrid and the phase of the grid current Igrid. The phase of the capacitor voltage Vcs lags behind the capacitor current Ics by π/2.

As described above, in the auxiliary inverter 50, the multiple upper-stage switching elements 50U and multiple lower-stage switching elements 50L are switched and controlled so that the phase of the current flowing through the active filter capacitor Cs matches the phase of the AC current in the AC-DC converter of the first circuit 1. The active decoupling circuit attenuates the AC harmonic components in the first circuit 1 by passing them through the active filter capacitor Cs. By matching the phase of the current flowing through the active filter capacitor Cs to the phase of the AC current in the first circuit 1, the attenuation effect can be increased.

As described above, in this embodiment, it is necessary to pass a current (capacitor current Ics) corresponding to the AC component Prpl, which is a pulsating component of the first DC power, through the active decoupling circuit. For this reason, the capacitor current command I ^* cs is set in consideration of the magnitude relationship with the output voltage (=battery voltage Vbat) for the DC power supply 3.

The capacitor voltage Vcs needs to be lower than the battery voltage Vbat. In addition, since pulsation corresponding to the AC component Prpl of the first DC power occurs in the capacitor voltage Vcs, the capacitor voltage Vcs is set to a voltage lower than the battery voltage Vbat in consideration of the amplitude of the pulsation. That is, it is preferable that the amplitude "V ^* cs_peak" of the capacitor voltage command V ^* cs, which is the command value of the capacitor voltage Vcs, is set so as to satisfy the following formula (6) with the amplitude (value from the amplitude center to the wave height (peak)) of the AC component "Vrpl" of the voltage in the first DC power being "Vrpl_peak".

V ^* cs_peak < Vbat - Vrpl_peak (6)

In addition, since the battery voltage Vbat rises as the charging of the DC power supply 3 progresses, if the capacitor voltage command V ^* cs is constant, the difference between the capacitor voltage Vcs and the battery voltage Vbat increases, the capacitor current Ics increases, and the loss also increases. Therefore, it is preferable that the capacitor voltage Vcs rises while satisfying the formula (6) as the battery voltage Vbat rises. In other words, it is preferable that the capacitor voltage command V ^* cs is set so as to rise while satisfying the formula (6) as the battery voltage Vbat rises.

In the sixth example described above with reference to FIG. 7, the switching element 1S of the first circuit 1, the switching element 50S of the auxiliary inverter 50 used in the second circuit 2, and the switching element 5S of the traction inverter 5 are all MOSFETs. However, as in the seventh example shown in FIG. 9, all of these switching elements may be junction FETs.

As in the first, second, and third examples, the switching element 1S constituting the active rectifier in the first circuit 1 and the switching element 50S of the auxiliary inverter 50 constituting the chopper circuit in the second circuit 2 are preferably composed of gallium nitride switching elements.

Also, similar to the embodiment in which the second circuit 2 includes a step-down chopper circuit, the switching elements (switching element 1S and switching element 50S) used in the vehicle-mounted charging device 10 and the switching element 5S of the traction inverter 5 may be different types of elements. As in the eighth example shown in FIG. 10, the switching elements (switching element 1S and switching element 50S) used in the vehicle-mounted charging device 10 may be junction type FETs, and the switching element 5S of the traction inverter 5 may be MOSFETs. As in the ninth example shown in FIG. 11, the switching elements (switching element 1S and switching element 50S) used in the vehicle-mounted charging device 10 may be junction type FETs, and the switching element 5S of the traction inverter 5 may be IGBTs.

For example, in one embodiment, the traction inverter 5, which converts power between the DC on the DC power source 3 side and the multi-phase AC on the traction coil 7 side, is preferably configured with silicon switching elements (e.g., Si-IGBTs, etc.) or silicon carbide switching elements (e.g., SiC-MOSFETs, etc.), and the auxiliary inverter 50, which functions as the active rectifier of the first circuit 1 and the half-bridge circuit of the second circuit 2, is preferably configured with gallium nitride switching elements (e.g., GaN-HEMTs (High Electron Mobility Transistors)).

The higher the switching frequency of the active rectifier, the greater the power factor improvement effect and the pulsation suppression effect. Also, the higher the switching frequency of the chopper circuit of the second circuit 2, the greater the pulsation suppression effect. On the other hand, in driving and controlling the auxiliary rotating electric machine 8M and the traction rotating electric machine 7M, a switching frequency that is high enough to improve the power factor improvement and pulsation reduction effect of the on-board charging device 10 is not required. A larger current flows through the traction inverter 5 than the auxiliary inverter 50, and the transient current and transient voltage corresponding to the fluctuation of the required torque also tend to be larger. Therefore, it is necessary to use elements with higher current resistance and voltage resistance for the traction inverter 5 than for the auxiliary inverter 50. In addition, since elements that can handle higher switching frequencies are more expensive, if the traction inverter 5 is required to have all of high current resistance, high voltage resistance, and high switching frequency, the cost of the traction inverter 5 will be very high. By configuring the auxiliary inverter 50, which has lower current resistance and voltage resistance requirements than the traction inverter 5, with elements with a higher switching frequency, the total cost of the traction inverter 5 and the auxiliary inverter 50 can be reduced.

As described above, in this embodiment, an input inductor Li having an appropriate inductance is arranged in the first circuit 1, and the need to control the active rectifier at a short control period (high control frequency) to compensate for the small inductance is relatively low. Therefore, the active rectifier of the first circuit 1 is not prevented from being composed of silicon switching elements or silicon carbide switching elements, similar to the traction inverter 5. However, by configuring the active rectifier using switching elements with the same composition as the auxiliary inverter 50 that cooperates as the vehicle-mounted charging device 10, it is possible to control the vehicle-mounted charging device 10 more efficiently, and improvement in system efficiency can also be expected.

In recent years, it has been proposed to use the DC power source of an electric vehicle or hybrid vehicle as an emergency power source in the event of a disaster. The chopper circuit of the second circuit 2 functions as a step-down chopper from the first circuit 1 to the DC power source 3, and functions as a step-up chopper from the DC power source 3 to the first circuit 1. The first circuit 1 also has a full bridge circuit, and can function as a bidirectional power converter that not only converts AC to DC, but also converts DC to AC. In other words, the first circuit 1 performs DC-AC conversion, and commercial AC power can be output from the first circuit 1, and the DC power source 3 can be used as an emergency power source.

In common with the first to ninth examples, the vehicle-mounted charging device 10 of the present embodiment, which is configured to perform bidirectional power conversion from AC to DC (second DC power) and from DC (second DC power) to AC, can be configured as follows. When the vehicle-mounted charging device 10 charges the DC power source 3 from the external AC power source 4, the first circuit 1 functions as a unity power factor AC/DC boost converter UPF (Unity Power Factor), and the second circuit 2 functions as a DC/DC buck converter. When the vehicle-mounted charging device 10 functions as an emergency AC power source that outputs AC power using power stored in the DC power source 3, the second circuit 2 functions as a DC/DC boost converter, and the first circuit 1 functions as a unity power factor DC/AC buck converter UPF.

As described above by way of example of various embodiments, according to this embodiment, an on-board charging device can be configured that uses the coil and inverter of a rotating electric machine mounted on a vehicle to charge a DC power source connected to a traction rotating electric machine with power from an external AC power source, while suppressing increases in system costs.

1: First circuit, 1S: Switching element, 2: Second circuit, 3: DC power source, 4: External AC power source, 5: Traction inverter, 5S: Switching element, 7: Traction coil, 7M: Traction rotating motor, 7N: Neutral point, 8M: Auxiliary rotating motor, 8N: Neutral point, 10: On-board charging device, 50: Auxiliary inverter (inverter), 50S: Switching element, Co: Output capacitor (second circuit capacitor), Cs: Active filter capacitor

Claims (4)

An on-board charging device that is mounted on a vehicle including: an auxiliary rotating electric machine that is a rotating electric machine for driving a driven object other than a traction rotating electric machine that serves as a driving force source for wheels, the auxiliary rotating electric machine having a multi-phase coil connected to each other at a neutral point; a DC power source that supplies power to the auxiliary rotating electric machine and the traction rotating electric machine; and an inverter that converts power between a DC on the DC power source side and a multi-phase AC on the coil side of the auxiliary rotating electric machine, the on-board charging device charging the DC power source with power supplied from an external AC power source,
a first circuit including an AC/DC converter for converting power between AC power from the external AC power source and a first DC power;
a second circuit that generates a second DC power for charging the DC power supply by attenuating a pulsating component from the first DC power,
the first circuit includes an active rectifier having a power factor correction function;
the second circuit includes a half-bridge circuit disposed on a side of the AC-DC converter, a second circuit inductor disposed on a side of the DC power source, and a second circuit capacitor;
The half-bridge circuit is configured using the inverter,
the second circuit inductor is configured using a plurality of the coils;
An on-board charging device, wherein the second circuit capacitor is connected between the neutral point of the coil and the negative terminal of the second circuit. the second circuit is a DC-DC converter including a chopper circuit that converts power between the first DC power and the second DC power,
the second circuit inductor is a reactor of the chopper circuit,
2. The vehicle-mounted charging device of claim 1, wherein the second circuit capacitor is an output capacitor connected in parallel with the DC power source. the second circuit is an active decoupling circuit in which a DC side of the inverter is connected to a DC side of the first circuit without any passive components;
2. The vehicle-mounted charging device according to claim 1, wherein the second circuit capacitor is an active filter capacitor connected between the neutral point of the coil and the negative electrode of the second circuit without being connected to the DC power supply. The traction rotating electric machine includes a multi-phase traction coil,
a traction inverter that converts power between a direct current on the side of the DC power supply and a multi-phase alternating current on the side of the traction coil is configured with silicon switching elements or silicon carbide switching elements;
4. The on-board charging device according to claim 1, wherein the active rectifier and the inverter functioning as a half-bridge circuit of the second circuit are configured using gallium nitride switching elements so as to be switched-controlled at a switching frequency higher than that of the traction inverter.

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