阅读说明：本技术 一种电驱动系统、动力总成及电动汽车 (Electric drive system, power assembly and electric automobile ) 是由 章雪亮 封宁波 陈跃 于 2020-10-21 设计创作，主要内容包括：本申请提供了一种电驱动系统、动力总成及电动汽车,涉及电子电路技术领域。其中,该电驱动系统包括：母线、车载充电机、三电平逆变电路和控制器。母线包括正母线和负母线,用于连接三电平逆变电路的输入端；车载充电机包括功率变换电路、可控谐振电路和整流电路；功率变换电路的输入端为车载充电机的输入端,功率变换电路的输出端通过可控谐振电路连接整流电路；整流电路的第一输出端连接正母线,整流电路的第二输出端连接负母线,整流电路的第三输出端连接母线中点；控制器当三电平逆变电路工作时,控制可控谐振电路和整流电路的工作状态,以使母线中点的电位平衡。利用该电驱动系统,提升了三电平逆变电路的母线中点电位均衡的调节能力。(The application provides an electric drive system, a power assembly and an electric automobile, and relates to the technical field of electronic circuits. Wherein, this electric drive system includes: the system comprises a bus, a vehicle-mounted charger, a three-level inverter circuit and a controller. The bus comprises a positive bus and a negative bus and is used for connecting the input end of the three-level inverter circuit; the vehicle-mounted charger comprises a power conversion circuit, a controllable resonance circuit and a rectification circuit; the input end of the power conversion circuit is the input end of the vehicle-mounted charger, and the output end of the power conversion circuit is connected with the rectifying circuit through the controllable resonant circuit; the first output end of the rectifying circuit is connected with the positive bus, the second output end of the rectifying circuit is connected with the negative bus, and the third output end of the rectifying circuit is connected with the midpoint of the bus; when the three-level inverter circuit works, the controller controls the working states of the controllable resonant circuit and the rectifying circuit so as to balance the potential of the midpoint of the bus. By utilizing the electric drive system, the adjustment capability of the neutral point potential balance of the bus of the three-level inverter circuit is improved.)

1. An electric drive system, characterized in that the electric drive system comprises: the system comprises a bus, a vehicle-mounted charger, a three-level inverter circuit and a controller; wherein the content of the first and second substances,

the bus comprises a positive bus and a negative bus and is used for connecting the input end of the three-level inverter circuit;

the vehicle-mounted charger comprises a power conversion circuit, a controllable resonance circuit and a rectification circuit;

the input end of the power conversion circuit is the input end of the vehicle-mounted charger, and the output end of the power conversion circuit is connected with the rectifying circuit through the controllable resonant circuit;

the first output end of the rectifying circuit is connected with the positive bus, the second output end of the rectifying circuit is connected with the negative bus, and the third output end of the rectifying circuit is connected with the midpoint of the bus;

and the controller is used for controlling the working states of the controllable resonant circuit and the rectifying circuit when the three-level inverter circuit works so as to balance the potential of the midpoint of the bus.

2. The electric drive system of claim 1, wherein the controllable resonant circuit comprises a controllable switch and a resonant unit;

the first output end of the power conversion circuit is connected with the first input end of the rectifying circuit through the resonance unit, the second output end of the power conversion circuit is connected with the second input end of the rectifying circuit, and the controllable switch is connected between the first output end and the second output end of the power conversion circuit;

and the controller is used for controlling the controllable switch to be closed when the three-level inverter circuit works and balancing the potential of the midpoint of the bus by controlling the working state of the rectifying circuit.

3. The electric drive system of claim 1, wherein the controllable resonant circuit comprises a first controllable switch, a second controllable switch, and a resonant unit;

the first output end of the power conversion circuit is connected with the first end of the first controllable switch and the first input end of the rectifying circuit through the second controllable switch, and the second end of the first controllable switch is connected with the second output end of the power conversion circuit and the second input end of the rectifying circuit through the resonance unit;

and the controller is used for controlling the first controllable switch to be closed and the second controllable switch to be disconnected when the three-level inverter circuit works, and balancing the potential of the midpoint of the bus by controlling the working state of the rectifying circuit.

4. An electric drive system according to claim 2 or 3, characterized in that the resonance unit comprises a first inductance and a first capacitance connected in series.

5. The electric drive system of claim 4, wherein the three-level inverter circuit comprises a bus capacitor;

and the switching frequency of the control signal of the rectifier circuit by the controller is equal to the resonant frequency of a series resonant circuit formed by the first inductor, the first capacitor and the bus capacitor.

6. The electric drive system of claim 5, wherein the rectifying circuit comprises a first switching tube, a second switching tube, a third switching tube and a fourth switching tube;

the first end of the first switch tube is connected with the first output end of the rectification circuit, the second end of the first switch tube is connected with the first input end of the rectification circuit and the first end of the second switch tube, the second end of the second switch tube is connected with the third output end of the rectification circuit and the first end of the third switch tube, the second end of the third switch tube is connected with the second input end of the rectification circuit and the first end of the fourth switch tube, and the second end of the fourth switch tube is connected with the second output end of the rectification circuit.

7. The electric drive system of claim 6 wherein the controller controls the first and third switching tubes with a first control signal and controls the second and fourth switching tubes with a second control signal, the first and second control signals being complementary and having the same duty cycle.

8. The electric drive system of claim 1, wherein the power conversion circuit is an LLC resonant conversion circuit.

9. The electric drive system of claim 1, wherein the controller is further configured to control an operating state of the onboard charger and/or the three-level inverter circuit.

10. The electric drive system of claim 2, wherein the controller is further configured to control the controllable switch to open when the input of the power conversion circuit is coupled to an ac power source.

11. The electric drive system of claim 3, wherein the controller is further configured to control the first controllable switch to open and the second controllable switch to close when the input of the power conversion circuit is externally connected to an AC power source.

12. A powertrain comprising an electric drive system of any of claims 1-11, and further comprising an electric machine;

the motor is connected with the output end of the three-level inverter circuit;

the motor is used for converting electric energy into mechanical energy to drive the electric automobile.

13. An electric vehicle comprising the powertrain of claim 12, and further comprising a power battery pack;

the power battery pack is used for providing a required direct current power supply for the power assembly.

14. The utility model provides a vehicle-mounted machine that charges, the input of vehicle-mounted machine that charges is used for connecting alternating current power supply, its characterized in that, vehicle-mounted machine that charges includes: the power conversion circuit, the controllable resonance circuit and the rectification circuit;

the input end of the power conversion circuit is the input end of the vehicle-mounted charger, and the output end of the power conversion circuit is connected with the rectifying circuit through the controllable resonant circuit;

the first output end of the rectifying circuit is used for being connected with a positive bus, the second output end of the rectifying circuit is used for being connected with a negative bus, and the third output end of the rectifying circuit is used for being connected with the midpoint of the bus.

15. The vehicle-mounted charger according to claim 14, characterized in that the controllable resonance circuit comprises a controllable switch and a resonance unit;

the first output end of the power conversion circuit is connected with the first input end of the rectifying circuit through the resonance unit, the second output end of the power conversion circuit is connected with the second input end of the rectifying circuit, and the controllable switch is connected between the first output end and the second output end of the power conversion circuit.

16. The vehicle-mounted charger according to claim 14, characterized in that the controllable resonance circuit comprises a first controllable switch, a second controllable switch and a resonance unit;

the first output end of the power conversion circuit is connected with the first end of the first controllable switch and the first input end of the rectifying circuit through the second controllable switch, and the second end of the first controllable switch is connected with the second output end of the power conversion circuit and the second input end of the rectifying circuit through the resonant circuit.

17. The vehicle-mounted charger according to claim 15 or 16, characterized in that said resonance unit comprises a first inductance and a first capacitance connected in series.

18. The vehicle-mounted charger according to claim 14, wherein the rectification circuit comprises a first switching tube, a second switching tube, a third switching tube and a fourth switching tube;

the first end of the first switch tube is connected with the first output end of the rectification circuit, the second end of the first switch tube is connected with the first input end of the rectification circuit and the first end of the second switch tube, the second end of the second switch tube is connected with the third output end of the rectification circuit and the first end of the third switch tube, the second end of the third switch tube is connected with the second input end of the rectification circuit and the first end of the fourth switch tube, and the second end of the fourth switch tube is connected with the second end of the rectification circuit.

19. The vehicle-mounted charger according to claim 14, wherein said power conversion circuit is an LLC resonant conversion circuit.

Technical Field

The application relates to the technical field of electronic power, in particular to an electric drive system, a vehicle-mounted charger, a power assembly and an electric automobile.

Background

With the shortage of energy and the aggravation of environmental pollution in modern society, electric vehicles have received wide attention from all over as new energy vehicles. Since the electric drive system of the electric vehicle directly affects the safety and efficiency of the electric vehicle, the electric drive system has been a research hotspot.

Compared with a conventional two-level electric drive system, the three-level electric drive system can effectively improve the NEDC (New European Driving Cycle) efficiency of the electric drive system, reduce the harmonic content of the output voltage, optimize the electromagnetic interference performance and the like, and thus is gradually a subject to be researched.

The three-level electric drive system comprises a three-level Motor Control Unit (MCU) and mainly comprises a three-level inverter circuit.

Referring to fig. 1, a schematic diagram of a three-level inverter circuit in the prior art is shown.

The three-level inverter circuit 10 is configured to convert the dc power provided by the power battery into ac power and provide the ac power to the motor 20. The degree of balance of the bus midpoint (point O in the figure) potential of the three-level inverter circuit 10 directly affects the performance of the three-level electric drive system, and therefore how to balance the bus midpoint potential is important.

In the prior art, the bus midpoint potential of the three-level inverter circuit 10 can be adjusted in a software control mode based on Space Vector Pulse Width Modulation (SVPWM), but the adjustment capability of the mode is limited, and when the bus midpoint potential offset is large, the bus midpoint potential is difficult to balance.

Disclosure of Invention

In order to solve the problems in the prior art, the application provides an electric drive system, a vehicle-mounted charger, a power assembly and an electric automobile, and the adjustment capacity of neutral point potential balance of a bus of a three-level inverter circuit is improved.

In a first aspect, the present application provides an electric drive system comprising: the system comprises a bus, a vehicle-mounted charger, a three-level inverter circuit and a controller. The bus comprises a positive bus and a negative bus and is used for connecting the input end of the three-level inverter circuit. The vehicle-mounted charger comprises a power conversion circuit, a controllable resonance circuit and a rectification circuit. The input end of the power conversion circuit is the input end of the vehicle-mounted charger, and the power conversion circuit is connected with an alternating current power supply when the vehicle-mounted charger is charged. The output end of the power conversion circuit is connected with the rectification circuit through the controllable resonant circuit. The first output end of the rectifying circuit is connected with the positive bus, the second output end of the rectifying circuit is connected with the negative bus, and the third output end of the rectifying circuit is connected with the midpoint of the bus. When the three-level inverter circuit works, the controller controls the working states of the controllable resonant circuit and the rectifying circuit so as to balance the potential of the midpoint of the bus.

The application provides an electric drive system, through multiplexing in order to realize three level inverter circuit's generating line midpoint potential equilibrium to on-vehicle machine that charges. When the three-level inverter circuit works, the input end of the vehicle-mounted charger is not connected with an alternating current power supply, the controller controls the working states of the controllable resonant circuit and the rectifying circuit, so that the controllable resonant circuit, the rectifying circuit and the bus capacitors of the three-level inverter circuit form a resonant voltage-sharing circuit, further energy transfer among the bus capacitors is realized, the potential of the midpoint of the bus is balanced, and the three-level inverter circuit also has good regulating capability when the potential offset of the midpoint of the bus is large.

In addition, the rectifying circuit of the existing vehicle-mounted charger is multiplexed, so that the hardware cost is lower when the technical scheme is realized, a complex hardware circuit is not required to be added, and the volume of an electric drive system cannot be obviously increased.

With reference to the first aspect, in a first possible implementation manner, the controllable resonant circuit includes a controllable switch and a resonant unit. The first output end of the power conversion circuit is connected with the first input end of the rectifying circuit through the resonance unit, the second output end of the power conversion circuit is connected with the second input end of the rectifying circuit, and the controllable switch is connected between the first output end and the second output end of the power conversion circuit. The controller is used for controlling the controllable switch to be closed when the three-level inverter circuit works so as to bypass the power conversion circuit of the vehicle-mounted charger, and the potential of the midpoint of the bus is balanced by controlling the working state of the rectifying circuit.

When the vehicle-mounted charger is a bidirectional vehicle-mounted charger, the resonant circuit can directly multiplex circuit devices such as capacitors and inductors of the bidirectional vehicle-mounted charger, and only the controllable switch is added, so that the hardware cost of the technical scheme is low, a complex hardware circuit is not required to be added, the volume of an electric drive system cannot be obviously increased, and the implementation of the scheme is facilitated.

With reference to the first aspect, in a second possible implementation manner, the controllable resonant circuit includes a first controllable switch, a second controllable switch, and a resonant unit. The first output end of the power conversion circuit is connected with the first end of the first controllable switch and the first input end of the rectification circuit through the second controllable switch, and the second end of the first controllable switch is connected with the second output end of the power conversion circuit and the second input end of the rectification circuit through the resonance unit. When the three-level inverter circuit works, the controller controls the first controllable switch to be closed and the second controllable switch to be disconnected, at the moment, the power conversion circuit of the vehicle-mounted charger is not connected, and the potential of the midpoint of the bus is balanced by controlling the working state of the rectification circuit.

The scheme is applied to the one-way vehicle-mounted charger, and only simple controllable switches and resonant circuits are added, so that the hardware cost of the technical scheme is low when the technical scheme is realized, the volume of an electric drive system cannot be obviously increased, and the implementation of the scheme is facilitated.

With reference to the first aspect, in a third possible implementation manner, the resonance unit includes a first inductor and a first capacitor connected in series. The first inductor, the first capacitor and the bus capacitor in the current loop form a series resonant loop.

With reference to the first aspect, in a fourth possible implementation manner, the three-level inverter circuit includes a bus capacitor. The bus capacitor of the three-level inverter circuit comprises a first bus capacitor and a second bus capacitor. The first bus capacitor is connected between the positive bus and the bus midpoint, and the second bus capacitor is connected between the negative bus and the bus midpoint. The switching frequency of the control signal of the rectifier circuit is equal to the resonant frequency of a series resonant circuit formed by the first inductor, the first capacitor and the bus capacitor. And the first bus capacitor and the second bus capacitor are connected with a series resonance circuit formed by the first inductor and the first capacitor in turn.

With reference to the first aspect, in a fifth possible implementation manner, the rectification circuit includes a first switching tube, a second switching tube, a third switching tube, and a fourth switching tube. The first end of the first switch tube is connected with the first output end of the rectification circuit, the second end of the first switch tube is connected with the first input end of the rectification circuit and the first end of the second switch tube, the second end of the second switch tube is connected with the third output end of the rectification circuit and the first end of the third switch tube, the second end of the third switch tube is connected with the second input end of the rectification circuit and the first end of the fourth switch tube, and the second end of the fourth switch tube is connected with the second output end of the rectification circuit.

With reference to the first aspect, in a sixth possible implementation manner, the controller controls the first switching tube and the third switching tube with the first control signal, and controls the second switching tube and the fourth switching tube with the second control signal, where the first control signal and the second control signal are complementary and have the same duty ratio, that is, the duty ratios are both 50%.

With reference to the first aspect, in a seventh possible implementation manner, the power conversion circuit of the vehicle-mounted charger is an LLC resonant conversion circuit.

With reference to the first aspect, in an eighth possible implementation manner, the controller is further configured to control an operating state of a vehicle-mounted charger and/or a three-level inverter circuit. Namely, the controller can be integrated with the controller of the vehicle-mounted charger, or the controller is integrated with the controller of the three-level inverter circuit, or the controller is integrated with the controller of the vehicle-mounted charger and the controller of the three-level inverter circuit.

With reference to the first aspect, in a ninth possible implementation manner, the controller is further configured to control the controllable switch to be turned off when the input end of the power conversion circuit is externally connected to an ac power supply.

With reference to the first aspect, in a tenth possible implementation manner, the controller is further configured to control the first controllable switch to be turned off and the second controllable switch to be turned on when the input end of the power conversion circuit is externally connected to an ac power supply.

In a second aspect, the present application further provides a vehicle-mounted charger, wherein an input end of the vehicle-mounted charger is connected to an ac power supply, and the vehicle-mounted charger includes: the controllable resonant circuit comprises a power conversion circuit, a controllable resonant circuit and a rectifying circuit. The input end of the power conversion circuit is the input end of the vehicle-mounted charger, and the output end of the power conversion circuit is connected with the rectification circuit through the controllable resonance circuit. The first output end of the rectifying circuit is used for being connected with a positive bus, the second output end of the rectifying circuit is used for being connected with a negative bus, and the third output end of the rectifying circuit is used for being connected with the midpoint of the bus.

With reference to the second aspect, in a first possible implementation manner, the vehicle-mounted charger is a bidirectional vehicle-mounted charger, and the controllable resonant circuit of the bidirectional vehicle-mounted charger includes a controllable switch and a resonant unit. The first output end of the power conversion circuit is connected with the first input end of the rectifying circuit through the resonance unit, the second output end of the power conversion circuit is connected with the second input end of the rectifying circuit, and the controllable switch is connected between the first output end and the second output end of the power conversion circuit.

The resonance circuit can directly multiplex circuit devices such as capacitors and inductors of the bidirectional vehicle-mounted charger, and only the controllable switch is added, so that the hardware cost of the technical scheme is low, the volume of an electric drive system cannot be obviously increased, and the implementation of the scheme is facilitated.

With reference to the second aspect, in a second possible implementation manner, the vehicle-mounted charger is a unidirectional vehicle-mounted charger, and the controllable resonant circuit of the unidirectional vehicle-mounted charger includes a first controllable switch, a second controllable switch, and a resonant unit. The first output end of the power conversion circuit is connected with the first end of the first controllable switch and the first input end of the rectification circuit through the second controllable switch, and the second end of the first controllable switch is connected with the second output end of the power conversion circuit and the second input end of the rectification circuit through the resonance circuit.

According to the scheme, only a simple controllable switch and a simple resonant circuit are added, so that the hardware cost is lower when the technical scheme is realized, the volume of an electric drive system cannot be obviously increased, and the implementation of the scheme is facilitated.

With reference to the second aspect, in a third possible implementation manner, the resonance unit includes a first inductor and a first capacitor connected in series.

With reference to the second aspect, in a fourth possible implementation manner, the rectification circuit includes a first switching tube, a second switching tube, a third switching tube, and a fourth switching tube. The first end of the first switch tube is connected with the first output end of the rectification circuit, the second end of the first switch tube is connected with the first input end of the rectification circuit and the first end of the second switch tube, the second end of the second switch tube is connected with the third output end of the rectification circuit and the first end of the third switch tube, the second end of the third switch tube is connected with the second input end of the rectification circuit and the first end of the fourth switch tube, and the second end of the fourth switch tube is connected with the second output end of the rectification circuit.

With reference to the second aspect, in a fifth possible implementation manner, the power conversion circuit is an LLC resonant conversion circuit.

In a third aspect, the present application further provides a control method of an electric drive system, for controlling the electric drive system provided in the above implementation manner, the method including: when the three-level inverter circuit works, the controllable switch is controlled to bypass the power conversion circuit and enable the resonant circuit to be connected into the circuit; the first switch tube and the third switch tube are controlled by a first control signal, the second switch tube and the fourth switch tube are controlled by a second control signal, the first control signal and the second control signal are complementary, the duty ratios of the first control signal and the second control signal are the same, and the switching frequency of the first control signal and the switching frequency of the second control signal are equal to the resonant frequency of a series resonance circuit formed by the first inductor, the first capacitor and the bus capacitor.

By using the control method, the bus capacitors of the controllable resonant circuit, the rectifying circuit and the three-level inverter circuit can form a resonant voltage-sharing circuit, so that energy transfer among the bus capacitors is realized, the potential at the midpoint of the bus is balanced, and a good adjusting effect can be achieved when the potential offset of the midpoint of the bus is large. In addition, when the method is realized, the controllable switch tubes in the rectifying circuit realize zero current switching-on and zero current switching-off, the loss of the switch tubes is low, and the efficiency is high.

In a fourth aspect, the present application further provides a power assembly, including the electric drive system provided in the foregoing implementation manner, and further including a motor. Wherein, the motor is connected with the output end of the three-level inverter circuit. The motor is used for converting electric energy into mechanical energy to drive the electric automobile.

By utilizing the power assembly, the advantages of a three-level electric drive system can be fully exerted, the efficiency of the power assembly is effectively improved, the harmonic content of output voltage is reduced, and the electromagnetic interference performance is optimized.

In a fifth aspect, the present application further provides an electric vehicle, which includes the power assembly provided above, and further includes a power battery pack. The power battery pack is used for providing a required direct current power supply for the power assembly.

Drawings

FIG. 1 is a schematic diagram of a three-level inverter circuit according to the prior art;

FIG. 2 is a schematic diagram of a corresponding three-level electric drive system of FIG. 1;

FIG. 3 is a schematic diagram of an electric drive system provided by an embodiment of the present application;

fig. 4A is a schematic diagram of a midpoint clamping type three-level inverter circuit according to an embodiment of the present disclosure;

fig. 4B is a schematic diagram of another midpoint clamping type three-level inverter circuit according to an embodiment of the present disclosure;

fig. 5 is a schematic diagram of an active midpoint clamping type three-level inverter circuit according to an embodiment of the present disclosure;

FIG. 6 is a schematic illustration of another electric drive system provided by an embodiment of the present application;

FIG. 7A is a first schematic diagram of a simulation waveform provided in the present embodiment;

fig. 7B is a schematic diagram of a simulation waveform provided in the embodiment of the present application;

FIG. 8 is a schematic illustration of yet another electric drive system provided by an embodiment of the present application;

fig. 9 is a schematic diagram of a vehicle-mounted charger according to an embodiment of the present application;

fig. 10 is a schematic diagram of another vehicle-mounted charger according to an embodiment of the present application;

FIG. 11 is a flow chart illustrating a method for controlling an electric drive system according to an exemplary embodiment of the present disclosure;

FIG. 12 is a schematic illustration of a powertrain according to an embodiment of the present disclosure;

fig. 13 is a schematic view of an electric vehicle according to an embodiment of the present application.

Detailed Description

In order to make the technical solutions provided by the embodiments of the present application better understood by those skilled in the art, a three-level electric drive system of an electric vehicle is first described below.

Referring to fig. 2, a schematic diagram of the corresponding three-level electric drive system of fig. 1 is shown.

The three-level electric drive system adopts an On-board Charger (OBC) 30 to convert alternating current input by an external power supply into direct current for charging a power battery pack of an electric vehicle.

The output end of a vehicle-mounted charger 30 of the electric vehicle and the input end of the three-level conversion circuit 10 (i.e., the input end of the three-level motor control unit) are connected in parallel on the direct current bus. When the vehicle-mounted charger 30 charges the power battery pack through the direct current bus, the three-level conversion circuit 10 does not work; when the electric vehicle is running, the three-level conversion circuit 10 works to convert the direct current provided by the power battery pack into alternating current and provide the alternating current to the motor 20, and at this time, the vehicle-mounted charger 30 is in an idle state.

The potential balance degree of the midpoint O in the bus of the three-level inverter circuit 10 directly affects various indexes such as harmonic waves of the output current of the three-level inverter circuit 10, withstand voltage of a power device and the like. In the prior art, the bus midpoint potential of the three-level inverter circuit 10 can be adjusted in a software control mode based on SVPWM, but the adjustment capability of the mode is limited.

For example, in some scenarios, the modulation ratio of the three-level inverter circuit 10 is high, and the power factor is low, and at this time, the voltage fluctuation of several tens of volts may occur in the bus midpoint potential, which exceeds the regulation range of the software control mode.

In order to solve the problems in the prior art, the application provides an electric drive system, a control method, a vehicle-mounted charger, a power assembly and an electric automobile. The scheme has the advantages of low hardware cost in implementation, no obvious increase of the volume of an electric drive system, and easy implementation.

The terms "first", "second", and the like in the description of the present application are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated.

In the present application, unless expressly stated or limited otherwise, the term "coupled" is to be construed broadly, e.g., "coupled" may be a fixed connection, a removable connection, or an integral part; may be directly connected or indirectly connected through an intermediate.

The first embodiment is as follows:

the embodiment of the application provides an electric drive system for controlling the neutral point potential balance of a bus of a three-level inverter circuit, which is specifically described below with reference to the accompanying drawings.

Referring to fig. 3, a schematic diagram of an electric drive system according to an embodiment of the present application is shown.

The electric drive system comprises a bus, a three-level inverter circuit 10, a vehicle-mounted charger 30 and a controller 40.

The bus bars include a positive bus bar (denoted by P in the figure) and a negative bus bar (denoted by N in the figure).

The vehicle-mounted charger 30 includes a power conversion circuit 301, a controllable resonance circuit 302, and a rectification circuit 303.

The input end of the power conversion circuit 301 is the input end of the vehicle-mounted charger 30, and the output end of the power conversion circuit 301 is connected with the rectifying circuit 303 through the controllable resonant circuit 302.

In some embodiments, the Power conversion circuit 301 includes a PFC (Power Factor Correction) circuit and a DC (Direct Current) -AC (Alternating Current) circuit. The PFC circuit converts the connected AC power into DC power and transmits the DC power to the DC-AC circuit, and the DC-AC circuit converts the DC power into AC power and transmits the AC power to the rectifier circuit 303.

The first output end of the rectifying circuit 303 is connected with the positive bus P, the second output end of the rectifying circuit 303 is connected with the negative bus N, and the third output end of the rectifying circuit 303 is connected with the bus midpoint O.

The three-level inverter circuit 10 may be a Neutral Point Clamped (NPC) type three-level inverter circuit.

Referring to fig. 4A and 4B together, a schematic diagram of the midpoint clamping type three-level inverter circuit is shown. Fig. 4A is a schematic diagram of a power circuit 101 of a midpoint clamping type three-level inverter circuit in a "T" connection. Fig. 4B shows a schematic diagram of the power circuit 101 of the midpoint clamping type three-level inverter circuit when the connection is an "I" connection.

The three-level inverter circuit 10 may also be an Active Neutral Point Clamped (ANPC) type three-level inverter circuit, and a schematic diagram of a power circuit thereof may be shown in fig. 5.

The working principle and the control mode of the three-level inverter circuit are mature technologies, and the embodiment of the application is not described herein again.

The three-level inverter circuit comprises a first bus capacitor C1 and a second bus capacitor C2. The first bus capacitor C1 is connected between the positive bus and the bus midpoint, and the second bus capacitor C2 is connected between the negative bus and the bus midpoint. The capacitance values of the first bus capacitor C1 and the second bus capacitor C2 are the same.

When the input end of the vehicle-mounted charger 30 is connected with the alternating current power supply, the vehicle-mounted charger 30 charges the power battery pack of the electric vehicle, that is, the electric vehicle is in a charging state at the moment, and the three-level inverter circuit 10 does not work.

When the three-level inverter circuit 10 works, the input end of the vehicle-mounted charger 30 is disconnected from the ac power supply, and the vehicle-mounted charger 30 in the prior art is in a stop working state at this time. In the present application, when the three-level inverter circuit 10 operates, the controller 40 controls the operating states of the controllable resonant circuit 302 and the rectifying circuit 303 to balance the potential at the midpoint of the bus, which will be described in detail below.

The controller 40 controls the working states of the controllable resonant circuit and the rectifying circuit, so that the controllable resonant circuit, the rectifying circuit and the bus capacitor form a resonant voltage-sharing circuit. The first bus capacitor C1 and the second bus capacitor C2 are alternately connected into the resonance voltage-sharing circuit.

When the absolute value of the voltage between the positive bus and the bus midpoint is larger than that between the negative bus and the bus midpoint, the resonance voltage-sharing circuit can transfer the electric quantity of the first bus capacitor C1 to the second bus capacitor C2, so that the potential of the bus midpoint is balanced; when the absolute value of the voltage between the positive bus and the bus midpoint is smaller than the absolute value of the voltage between the negative bus and the bus midpoint, the resonance voltage-sharing circuit can transfer the electric quantity of the second bus capacitor C2 to the first bus capacitor C1, so that the potential of the bus midpoint is balanced.

In some embodiments, the onboard charger 30 of the electric vehicle is a unidirectional onboard charger, i.e., the onboard charger utilizes the ac power grid to provide power to charge the power battery pack.

In other embodiments, the vehicle-mounted charger 30 of the electric vehicle is a bidirectional vehicle-mounted charger, when the input end of the vehicle-mounted charger 30 is connected to the ac power grid, the power battery pack of the electric vehicle can be used as the load end of the power grid, and at this time, the vehicle-mounted charger 30 charges the power battery pack by using the ac power grid to provide electric energy; the power battery pack may also feed back energy to the Grid through the on-board charger 30, i.e., the bi-directional on-board charger supports the V2G (Vehicle-to-Grid) function.

The controller 40 in this embodiment may be an Application Specific Integrated Circuit (ASIC), a Programmable Logic Device (PLD), a Digital Signal Processor (DSP), or a combination thereof. The PLD may be a Complex Programmable Logic Device (CPLD), a Field-Programmable Gate Array (FPGA), a General Array Logic (GAL), or any combination thereof, and the embodiment of the present invention is not limited thereto.

The controllable resonant circuit 302 and the rectifying circuit 303 include controllable switching tubes, and the embodiment of the present application does not specifically limit the types of the controllable switching tubes, and for example, the controllable switching tubes may be Insulated Gate Bipolar Transistors (IGBTs), Metal Oxide Semiconductor field Effect transistors (Metal Oxide Semiconductor field Effect transistors, MOSFETs, hereinafter referred to as MOS transistors), SiC MOSFETs (Silicon Carbide field Effect transistors), and the like.

The controller 40 can send a PWM (Pulse Width Modulation) signal to the controllable switch tube to control the operating state of the controllable switch tube.

To sum up, the electric drive system that this application embodiment provided, when three-level inverter circuit during operation, the controller is through the operating condition of control controllable resonant circuit and rectifier circuit for controllable resonant circuit, rectifier circuit and three-level inverter circuit's bus capacitance form resonance equalizer circuit, and then realize the energy transfer between the bus capacitance, make the electric potential of bus midpoint balanced, can also possess good regulation effect when the big offset of bus midpoint electric potential.

In addition, because the rectifying circuit of the existing vehicle-mounted charger is multiplexed, the hardware cost is lower when the technical scheme is realized, a complex hardware circuit is not required to be added, the volume of an electric drive system cannot be obviously increased, and the implementation of the scheme is facilitated.

The operation of the electric drive system is described below with reference to specific implementations. In the following description, a power circuit of a three-level inverter circuit is described by using a "T" type connection as an example, and the principle when the power circuit of the three-level inverter circuit uses an "I" type connection is similar, which is not described in detail in this application.

Example two:

in the embodiment of the present application, a vehicle-mounted charger is taken as an example of a bidirectional vehicle-mounted charger.

Referring to FIG. 6, another schematic diagram of an electric drive system provided in accordance with an embodiment of the present application is shown.

The illustrated vehicle-mounted charger 30 is a CLLC vehicle-mounted charger, and the power conversion circuit 301 is an LLC resonant conversion circuit.

The controllable resonance circuit 302 of the vehicle-mounted charger 30 comprises a controllable switch S and a resonance unit. The resonant cell comprises a first inductance L and a first capacitance Co connected in series.

In other embodiments, the first inductor L may further represent an equivalent inductance of a plurality of inductors, and the first capacitor may further represent an equivalent capacitance of a plurality of capacitors.

The controllable switch S may be a controllable switch tube.

The secondary winding of the CLLC type vehicle-mounted charger in the prior art can be connected in series with an inductor and a capacitor, that is, the first inductor L and the first capacitor Co of the resonant unit in the application can directly multiplex the inductor and the capacitor in the prior art, and the controllable resonant circuit 302 only adds the controllable switch S compared with the prior art, so that the influence on the cost and the volume is small.

A first output terminal of the power conversion circuit 301 is connected to a first input terminal of the rectifying circuit 303 through the resonance unit, a second output terminal of the power conversion circuit 302 is connected to a second input terminal of the rectifying circuit 303, and the controllable switch S is connected between the first output terminal and the second output terminal of the power conversion circuit.

The rectifying circuit 303 of the CLLC type vehicle-mounted charger in the prior art is generally a full-bridge rectifying circuit, and the topology of the rectifying circuit is improved in the embodiment of the application, specifically: the rectifying circuit 303 includes a first switching tube Q1, a second switching tube Q2, a third switching tube Q3 and a fourth switching tube. The first end of the first switching tube Q1 is connected to the first output end of the rectifying circuit 303, the second end of the first switching tube Q1 is connected to the first input end of the rectifying circuit 303 and the first end of the second switching tube Q2, the second end of the second switching tube Q2 is connected to the third output end of the rectifying circuit 303 and the first end of the third switching tube Q3, the second end of the third switching tube Q3 is connected to the second input end of the rectifying circuit 303 and the first end of the fourth switching tube Q4, and the second end of the fourth switching tube Q4 is connected to the second output end of the rectifying circuit 303.

Taking the switching transistors Q1-Q4 as NMOS transistors for example, the first terminals of the switching transistors Q1-Q4 are the drains thereof, and the second terminals thereof are the sources thereof.

Compared with the full-bridge rectifier circuit in the prior art, the rectifier circuit 303 in the embodiment of the present application does not increase the number of switching tubes used.

When the input end of the power conversion circuit is externally connected with an alternating current power supply, namely the vehicle-mounted charger 30 works, the controller controls the controllable switch S to be switched off.

When the three-level inverter circuit 10 operates, the controller controls the controllable switch S to be closed, and controls the operating state of the rectifying circuit 303 to balance the potential at the midpoint of the bus, which will be described in detail below.

When the three-level inverter circuit 10 works, the input end of the vehicle-mounted charger 30 is disconnected from the external alternating current power supply, and the controller controls the controllable switch S to be closed so as to bypass the power conversion circuit 301.

The controller controls the first switch tube Q1 and the third switch tube Q3 with a first control signal, controls the second switch tube Q2 and the fourth switch tube Q4 with a second control signal, and the first control signal and the second control signal are complementary and have the same duty ratio, i.e. the duty ratios are both 50%. Therefore, when the first switching tube Q1 and the third switching tube Q3 are turned on, the second switching tube Q2 and the fourth switching tube Q4 are turned off, and at this time, the first bus capacitor C1, the first inductor L and the first capacitor Co are connected to the same loop; when the first switch tube Q1 and the third switch tube Q3 are turned off, the second switch tube Q2 and the fourth switch tube Q4 are turned on, and at this time, the second bus capacitor C2, the first inductor L and the first capacitor Co are connected to the same loop.

Since the capacitance values of the first bus capacitor C1 and the second bus capacitor C2 are the same, the resonant frequency of the series resonant circuit formed by any one of the bus capacitors, the first inductor L and the first capacitor Co is the same. The controller uses the resonance frequency of the series resonant circuit as the switching frequency of the first control signal and the second control signal.

At the moment, the first inductor L, the first capacitor Co and the currently connected direct current bus capacitor form a resonant voltage-sharing circuit. When the absolute value of the voltage difference between the positive bus and the bus midpoint is greater than the absolute value of the voltage difference between the negative bus and the bus midpoint, the working state of Q1-Q4 is controlled, so that a first bus capacitor C1 and a second bus capacitor C2 alternately form a series resonant circuit with a first inductor L and a first capacitor Co, and further the first bus capacitor C1 transfers the electric quantity to a second bus capacitor C2 until the electric quantities of the first bus capacitor C1 and the second bus capacitor C2 are the same, and further the balance of the bus midpoint potential is realized; when the absolute value of the voltage difference between the positive bus and the bus midpoint is smaller than the absolute value of the voltage difference between the negative bus and the bus midpoint, the working state of Q1-Q4 is controlled, so that the first bus capacitor C1 and the second bus capacitor C2 alternately form a series resonance circuit with the first inductor L and the first capacitor Co, and further the second bus capacitor C2 transfers the electric quantity to the first bus capacitor C1 until the electric quantities of the second bus capacitor C2 and the first bus capacitor C1 are the same, and further the balance of the bus midpoint potential is realized.

In some embodiments, the controller may also control the operating state of the three-level inverter circuit 10, i.e., the controller may be integrated with the controller of the three-level inverter circuit 10.

In other embodiments, the controller may also control the operating state of the vehicle-mounted charger, that is, the controller may also be integrated with the controller of the vehicle-mounted charger 30.

To sum up, the electric drive system that this application embodiment provided, when three-level inverter circuit during operation, the controller is through the operating condition of control controllable resonant circuit and rectifier circuit for controllable resonant circuit, rectifier circuit and three-level inverter circuit's bus capacitance form resonance equalizer circuit, and then realize the energy transfer between the bus capacitance, make the electric potential of bus midpoint balanced, can also possess good regulation effect when the big offset of bus midpoint electric potential. Because the rectifying circuit of the existing vehicle-mounted charger is multiplexed, the technical scheme has lower hardware cost in implementation, does not need to increase complex hardware circuits, does not obviously increase the volume of an electric drive system, and is convenient for implementation of the scheme. The following specifically describes the beneficial effects of the technical solution of the present application with reference to the drawings.

Referring to fig. 7A, a schematic diagram of a simulation waveform provided in the embodiment of the present application is shown.

Fig. 7A shows simulation of the adjusting effect of the technical solution of the present application on the midpoint potential of the bus. Wherein Vc1 and Vc2 represent the absolute value of the positive bus voltage and the absolute value of the negative bus voltage, respectively. The technical scheme of the application is implemented after T is 0.02S.

As can be seen from the illustrated waveforms, the bus midpoint potential fluctuates widely until T becomes 0.02S, and the degree of deviation thereof reaches about 40V at maximum as seen from the waveforms corresponding to Vc1-Vc 2.

I (Rl1a), I (Rl1b) and I (Rl1c) respectively represent one-phase output current of the three-level inverter circuit, and it can be seen that the shift of the midpoint potential of the bus affects the harmonic waves of the output current, so that the waveform of the output current is distorted.

After T is 0.02S, the technical scheme of the application enables Vc1-Vc2 to be stably maintained at about 0V, even when the bus potential offset is large, the bus potential can be balanced, and the adjusting effect is obvious.

Referring to fig. 7B, a schematic diagram of a simulation waveform provided in the embodiment of the present application is shown.

Fig. 7B shows a relationship diagram of voltage and current between two ends of the switch tube in the rectifying circuit 303. Wherein Vmos1 is the voltage across Q1 and Q3, I (MOS1) is the current through Q1 and Q3; vmos2 is the voltage across Q2 and Q4, and I (MOS2) is the current through Q2 and Q4. It can be seen that, when the scheme of the application is implemented, the controllable switching tubes Q1-Q4 in the rectifying circuit 303 all implement zero-current turn-on and zero-current turn-off, and the switching tubes have low loss and high efficiency.

Example three:

the operating principle of the electric drive is explained below with reference to another specific implementation.

Referring to fig. 8, a schematic diagram of yet another electric drive system provided by an embodiment of the present application is shown.

The illustrated vehicle-mounted charger 30 is an LLC vehicle-mounted charger, and the power conversion circuit 301 is an LLC resonant conversion circuit.

The controllable resonance circuit 302 of the vehicle-mounted charger 30 comprises a first controllable switch S1, a second controllable unit S2 and a resonance unit. The resonant cell comprises a first inductance L and a first capacitance Co connected in series.

The first controllable switch S1 and the second controllable switch S2 may be controllable switch tubes.

A first output terminal of the power conversion circuit 301 is connected to a first terminal of the first controllable switch S1 and a first input terminal of the rectification circuit 303 through a second controllable unit S2, and a second terminal of the first controllable switch S1 is connected to a second output terminal of the power conversion circuit 301 and a second input terminal of the rectification circuit 303 through a resonance unit.

The rectifying circuit 303 of the LLC type vehicle-mounted charger in the prior art is generally a full-bridge rectifying circuit, and the topology of the rectifying circuit in the embodiment of the present application is improved, specifically: the rectifying circuit 303 includes a first switching tube Q1, a second switching tube Q2, a third switching tube Q3 and a fourth switching tube Q4. The first end of the first switching tube Q1 is connected to the first output end of the rectifying circuit 303, the second end of the first switching tube Q1 is connected to the first input end of the rectifying circuit 303 and the first end of the second switching tube Q2, the second end of the second switching tube Q2 is connected to the third output end of the rectifying circuit 303 and the first end of the third switching tube Q3, the second end of the third switching tube Q3 is connected to the second input end of the rectifying circuit 303 and the first end of the fourth switching tube Q4, and the second end of the fourth switching tube Q4 is connected to the second end of the rectifying circuit 303.

Taking the switching transistors Q1-Q4 as NMOS transistors for example, the first terminals of the switching transistors Q1-Q4 are the drains thereof, and the second terminals thereof are the sources thereof.

Compared with the full-bridge rectifier circuit in the prior art, the rectifier circuit 303 in the embodiment of the present application does not increase the number of switching tubes used.

When the input end of the power conversion circuit is externally connected with an alternating current power supply, namely the vehicle-mounted charger 30 works, the controller controls the first controllable switch S1 to be switched off and controls the second controllable switch S2 to be switched on.

When the three-level inverter circuit 10 operates, the controller controls the first controllable switch S1 to be closed, controls the second controllable switch S2 to be opened, and controls the operating state of the rectifying circuit 303 to balance the potential at the midpoint of the bus, which will be described in detail below.

The controller controls the first switch tube Q1 and the third switch tube Q3 with a first control signal, controls the second switch tube Q2 and the fourth switch tube Q4 with a second control signal, and the first control signal and the second control signal are complementary and have the same duty ratio, i.e. the duty ratios are both 50%.

When the first switching tube Q1 and the third switching tube Q3 are turned on, the second switching tube Q2 and the fourth switching tube Q4 are turned off, and at the moment, the first bus capacitor C1, the first inductor L and the first capacitor Co are connected to the same loop; when the first switch tube Q1 and the third switch tube Q3 are turned off, the second switch tube Q2 and the fourth switch tube Q4 are turned on, and at this time, the second bus capacitor C2, the first inductor L and the first capacitor Co are connected to the same loop.

Since the capacitance values of the first bus capacitor C1 and the second bus capacitor C2 are the same, the resonant frequency of the series resonant circuit formed by any one of the bus capacitors, the first inductor L and the first capacitor Co is the same. The controller uses the resonance frequency of the series resonant circuit as the switching frequency of the first control signal and the second control signal. At the moment, the first inductor L, the first capacitor Co and the currently connected direct current bus capacitor form a resonant voltage-sharing circuit.

When the absolute value of the voltage difference between the positive bus and the bus midpoint is greater than the absolute value of the voltage difference between the negative bus and the bus midpoint, the first bus capacitor C1 and the second bus capacitor C2 alternately form a series resonance circuit with the first inductor L and the first capacitor Co, so that the first bus capacitor C1 transfers the electric quantity to the second bus capacitor C2 until the electric quantities of the first bus capacitor C1 and the second bus capacitor C2 are the same, and further the balance of the bus midpoint potential is realized; when the absolute value of the voltage difference between the positive bus and the bus midpoint is smaller than the absolute value of the voltage difference between the negative bus and the bus midpoint, the first bus capacitor C1 and the second bus capacitor C2 alternately form a series resonance circuit with the first inductor L and the first capacitor Co, so that the second bus capacitor C2 transfers the electric quantity to the first bus capacitor C1 until the electric quantities of the second bus capacitor C2 and the first bus capacitor C1 are the same, and the balance of the bus midpoint potential is realized.

In some embodiments, the controller may also control the operating state of the three-level inverter circuit 10, i.e., the controller may be integrated with the controller of the three-level inverter circuit 10.

In other embodiments, the controller may also control the operating state of the vehicle-mounted charger, that is, the controller may also be integrated with the controller of the vehicle-mounted charger 30.

In summary, with the electric drive system provided in the embodiment of the present application, when the three-level inverter circuit works, the controller controls the working states of the controllable resonant circuit and the rectifying circuit, so that the controllable resonant circuit, the rectifying circuit and the bus capacitor of the three-level inverter circuit form a resonant voltage-sharing circuit, and further, energy transfer between the bus capacitors is realized, and the potential at the midpoint of the bus is balanced, so that a good adjusting effect can be achieved when the offset of the potential at the midpoint of the bus is large. The scheme reuses the rectifying circuit of the existing one-way vehicle-mounted charger, and only adds the simple controllable switch and the resonant circuit, so that the hardware cost of the technical scheme is lower when the technical scheme is realized, the complex hardware circuit does not need to be added, the volume of an electric drive system cannot be obviously increased, and the implementation of the scheme is convenient. In addition, when the scheme is realized, the controllable switching tubes in the rectifying circuit realize zero current switching-on and zero current switching-off, the loss of the switching tubes is low, and the efficiency is high.

Example four:

the embodiment of the application further provides a vehicle-mounted charger, which is applied to the electric drive system provided by the embodiment and is specifically described below with reference to the accompanying drawings.

Referring to fig. 9, a schematic diagram of a vehicle-mounted charger provided in the embodiment of the present application is shown.

The vehicle-mounted charger 30 shown in fig. 9 is a bidirectional vehicle-mounted charger, specifically, a CLLC vehicle-mounted charger, and specifically includes: a power conversion circuit 301, a controllable resonance circuit 302 and a rectification circuit 303.

The power conversion circuit 301 is an LLC resonant conversion circuit. The input end of the power conversion circuit 301 is the input end of the vehicle-mounted charger 30 and is used for connecting an alternating current power supply.

The controllable resonance circuit 302 comprises a controllable switch S and a resonance unit. The resonant cell comprises a first inductance L and a first capacitance Co connected in series. The controllable switch S may be a controllable switch tube.

The rectifying circuit 303 includes a first switching tube Q1, a second switching tube Q2, a third switching tube Q3 and a fourth switching tube Q4. The first end of the first switching tube Q1 is connected to the first output end of the rectifying circuit 303, the second end of the first switching tube Q1 is connected to the first input end of the rectifying circuit 303 and the first end of the second switching tube Q2, the second end of the second switching tube Q2 is connected to the third output end of the rectifying circuit 303 and the first end of the third switching tube Q3, the second end of the third switching tube Q3 is connected to the second input end of the rectifying circuit 303 and the first end of the fourth switching tube Q4, and the second end of the fourth switching tube Q4 is connected to the second output end of the rectifying circuit 303.

The first output end of the rectifying circuit 303 is used for connecting a positive bus, the third output end of the rectifying circuit 303 is used for connecting a negative bus, and the second output end of the rectifying circuit 303 is used for connecting a midpoint of the bus.

Referring to fig. 10, a schematic diagram of a vehicle-mounted charger provided in the embodiment of the present application is shown.

The vehicle-mounted charger 30 shown in fig. 10 is a bidirectional vehicle-mounted charger, specifically, a CLLC vehicle-mounted charger, and specifically includes: a power conversion circuit 301, a controllable resonance circuit 302 and a rectification circuit 303.

The power conversion circuit 301 is an LLC resonant conversion circuit. The input end of the power conversion circuit 301 is the input end of the vehicle-mounted charger 30 and is used for connecting an alternating current power supply.

The controllable resonance circuit 302 comprises a first controllable switch S1, a second controllable switch S2 and a resonance unit. The resonant cell comprises a first inductance L and a first capacitance Co connected in series. The controllable switch S may be a controllable switch tube.

The rectifying circuit 303 includes a first switching tube Q1, a second switching tube Q2, a third switching tube Q3 and a fourth switching tube Q4. The specific link mode of the rectifier circuit is the same as above, and is not described herein again.

To sum up, the vehicle-mounted charger provided by the embodiment of the application can normally charge the power battery pack of the electric automobile by controlling and controlling when the input end is connected with the alternating current power supply. When the three-level inverter circuit is not externally connected with an alternating current power supply and works, the controllable switch and the rectifying circuit are controlled by the controller, so that the controllable resonant circuit, the rectifying circuit and the bus capacitor of the three-level inverter circuit form a resonant voltage-sharing circuit, further energy transfer among the bus capacitors is realized, the potential of the midpoint of the bus is balanced, and the three-level inverter circuit also has a good adjusting effect when the potential offset of the midpoint of the bus is large. The technical scheme reuses the rectifying circuit of the conventional vehicle-mounted charger, so that the hardware cost is lower when the technical scheme is realized, a complex hardware circuit is not required to be added, the volume of an electric drive system cannot be obviously increased, and the scheme is convenient to implement. In addition, when the scheme is realized, the controllable switching tubes in the rectifying circuit realize zero current switching-on and zero current switching-off, the loss of the switching tubes is low, and the efficiency is high.

Example five:

based on the electric drive system provided by the above embodiments, embodiments of the present application further provide a control method of the electric drive system, which is specifically described below with reference to the accompanying drawings.

Referring to fig. 11, a flowchart of a control method of an electric drive system according to an embodiment of the present application is shown.

The method comprises the following steps:

s1101: when the three-level inverter circuit works, the controllable switch is controlled to bypass the power conversion circuit and enable the resonant circuit to be connected into the circuit.

S1102: the first switch tube and the third switch tube are controlled by a first control signal, the second switch tube and the fourth switch tube are controlled by a second control signal, the first control signal and the second control signal are complementary, the duty ratios of the first control signal and the second control signal are the same, and the switching frequency of the first control signal and the switching frequency of the second control signal are equal to the resonant frequency of a series resonance circuit formed by the first inductor, the first capacitor and the bus capacitor.

In summary, with the control method of the electric drive system provided in the embodiment of the present application, the controllable resonant circuit, the rectifying circuit, and the bus capacitor of the three-level inverter circuit can form a resonant voltage-sharing circuit, so as to implement energy transfer between the bus capacitors, balance the potential at the midpoint of the bus, and provide a good adjustment effect when the offset of the potential at the midpoint of the bus is large. In addition, when the method is realized, the controllable switch tubes in the rectifying circuit realize zero current switching-on and zero current switching-off, the loss of the switch tubes is low, and the efficiency is high.

Example six:

based on the electric drive system provided by the above embodiment, the embodiment of the present application further provides a power assembly of an electric vehicle, which is specifically described below with reference to the accompanying drawings.

Referring to fig. 12, the drawing is a schematic view of a power train of an electric vehicle according to an embodiment of the present application.

The powertrain 1200 provided by the embodiment of the present application includes an electric drive system 1201 and a motor 20.

The motor 20 is connected to an output end of the three-level inverter circuit, and the motor 20 is configured to convert the electric energy into mechanical energy to drive the electric vehicle.

The electric drive system 1201 comprises a bus, a three-level inverter circuit, a vehicle-mounted charger and a controller.

The bus bars include a positive bus bar and a negative bus bar.

The vehicle-mounted charger comprises a power conversion circuit, a controllable resonance circuit and a rectification circuit.

For specific implementation and operation principle of the electric drive system, reference may be made to the description in the above embodiments, and the embodiments of the present application are not described herein again.

To sum up, when the three-level inverter circuit works, the controller of the electric drive system of the power assembly controls the working states of the controllable resonant circuit and the rectifying circuit, so that the bus capacitors of the controllable resonant circuit, the rectifying circuit and the three-level inverter circuit form a resonant voltage-sharing circuit, and further energy transfer among the bus capacitors is realized, the potential of the midpoint of the bus is balanced, and the controller can also have a good adjusting effect when the potential offset of the midpoint of the bus is large. Because the rectifying circuit of the existing vehicle-mounted charger is multiplexed, the technical scheme has lower hardware cost in implementation, does not need to increase complex hardware circuits, does not obviously increase the volume of an electric drive system, and is convenient for implementation of the scheme.

In addition, when the scheme is realized, the controllable switch tubes in the rectifying circuit realize zero current switching-on and zero current switching-off, the loss of the switch tubes is low, and the efficiency is high. Therefore, the power assembly can fully exert the advantages of a three-level electric drive system, effectively improve the efficiency of the power assembly, reduce the harmonic content of the output voltage and optimize the electromagnetic interference performance.

Example seven:

based on the power assembly provided by the above embodiment, the embodiment of the application further provides an electric vehicle, which is specifically described below with reference to the accompanying drawings.

Referring to fig. 13, the drawing is a schematic view of an electric vehicle according to an embodiment of the present application.

The illustrated electric vehicle 1300 includes a powertrain 1200 and a power battery pack 1301.

The power battery pack 1301 is used to provide the required dc power to the powertrain 1200.

The powertrain 1200 provided by the embodiment of the present application includes an electric drive system 1201 and a motor 20.

The motor 20 is connected to an output end of the three-level inverter circuit, and the motor 20 is configured to convert the electric energy into mechanical energy to drive the electric vehicle.

The electric drive system 1201 comprises a bus, a three-level inverter circuit, a vehicle-mounted charger and a controller.

The bus bars include a positive bus bar and a negative bus bar.

The vehicle-mounted charger comprises a power conversion circuit, a controllable resonance circuit and a rectification circuit.

For specific implementation and operation principle of the electric drive system, reference may be made to the description in the above embodiments, and the embodiments of the present application are not described herein again.

In summary, the power assembly of the electric vehicle includes the electric drive system provided by the application, when the three-level inverter circuit works, the controller of the electric drive system controls the working states of the controllable resonance circuit and the rectifying circuit, so that the controllable resonance circuit, the rectifying circuit and the bus capacitor of the three-level inverter circuit form a resonance voltage-sharing circuit, and further energy transfer among the bus capacitors is realized, the potential of the midpoint of the bus is balanced, and a good adjusting effect can be achieved when the potential offset of the midpoint of the bus is large. Because the rectifying circuit of the existing vehicle-mounted charger is multiplexed, the technical scheme has lower hardware cost in implementation, does not need to increase complex hardware circuits, does not obviously increase the volume of an electric drive system, and is convenient for implementation of the scheme. In addition, when the scheme is realized, the controllable switch tubes in the rectifying circuit realize zero current switching-on and zero current switching-off, the loss of the switch tubes is low, and the efficiency is high. Therefore, the power assembly can fully exert the advantages of a three-level electric drive system, effectively improve the efficiency of the electric drive system, reduce the harmonic content of output voltage and optimize the electromagnetic interference performance, so that the electric automobile can effectively improve the NEDC efficiency after utilizing the power assembly.

It should be understood that in the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In addition, some or all of the units and modules may be selected according to actual needs to achieve the purpose of the solution of the embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

The foregoing is directed to embodiments of the present application and it is noted that numerous modifications and adaptations may be made by those skilled in the art without departing from the principles of the present application and are intended to be within the scope of the present application.