Electric vehicle electric drive system and control method thereof

Abstract

An embodiment of the present application provides an electric vehicle electric drive system and a control method thereof. In the electric vehicle electric drive system, by adding a switch module, the three-phase inverter circuit of the drive motor is divided into a first half-bridge circuit group and a second half-bridge circuit group. The first half-bridge circuit group is connected to the power battery system, and the second half-bridge circuit group is connected to the DC charging port. In this way, the existing three-phase inverter circuit power switch tube and motor winding inductance are reused to achieve boost charging, which greatly reduces the cost compared to adding a dedicated boost converter.

Description

Technical Field

[0001] The present application relates to the field of battery charging technology, and in particular to an electric vehicle electric drive system and a control method thereof. Background Art

[0002] With the booming development of new energy vehicles, power batteries are finding widespread use. A key charging method for power batteries is DC fast charging. This involves a DC charging station converting mains electricity into DC power and supplying it directly to the power battery. However, if the DC charging station's output voltage is lower than the power battery's voltage, the DC charging station will be unable to charge the power battery.

[0003] In the related art, a dedicated boost converter is generally used to increase the output voltage of the DC charging pile. However, the dedicated boost converter increases the cost of the entire vehicle. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide an electric vehicle electric drive system and a control method thereof, aiming to solve the problem in the related art that the boost solution for the output voltage of a DC charging pile relies on a dedicated boost converter, which increases the cost of the entire vehicle.

[0005] In a first aspect, an embodiment of the present application provides an electric drive system for an electric vehicle, comprising a power battery system, a three-phase inverter circuit, a drive motor and a switch module, wherein: the input end of the three-phase inverter circuit is connected to the power battery system, and the output end is connected to the drive motor; the three-phase inverter circuit comprises a first half-bridge circuit group and a second half-bridge circuit group, wherein the first half-bridge circuit group comprises a one-phase half-bridge circuit or a two-phase half-bridge circuit; the first half-bridge circuit group and the second half-bridge circuit group are connected through the switch module; the positive pole of the first half-bridge circuit group is connected to the positive pole of the power battery system, and the negative pole of the first half-bridge circuit group is connected to the negative pole of the power battery system; the positive pole of the second half-bridge circuit group is connected to the positive pole of the DC charging port, and the negative pole of the second half-bridge circuit group is connected to the negative pole of the DC charging port.

[0006] In the above implementation process, an electric vehicle electric drive system is provided. The electric drive system divides the three-phase inverter circuit of the drive motor into a first half-bridge circuit group and a second half-bridge circuit group by adding a switch module. The first half-bridge circuit group is connected to the power battery system, and the second half-bridge circuit group is connected to the DC charging port. In this way, the existing three-phase inverter circuit power switch tubes and motor winding inductors are reused to achieve boost charging, which greatly reduces the cost compared to adding a dedicated boost converter.

[0007] Furthermore, in some embodiments, the positive electrode of the first half-bridge circuit group and the positive electrode of the second half-bridge circuit group are connected through the switch module; the negative electrode of the first half-bridge circuit group and the negative electrode of the second half-bridge circuit group are directly connected.

[0008] In the above implementation process, one implementation solution of the electric vehicle power drive system is provided, that is, the positive poles of the two separate parts of the three-phase inverter circuit are connected together through a switch module.

[0009] Furthermore, in some embodiments, the negative electrode of the first half-bridge circuit group and the negative electrode of the second half-bridge circuit group are connected through the switch module; the positive electrode of the first half-bridge circuit group and the positive electrode of the second half-bridge circuit group are directly connected.

[0010] In the above implementation process, another implementation scheme of the electric vehicle power drive system is provided, that is, the negative electrodes of the two separate parts of the three-phase inverter circuit are connected together through a switch module.

[0011] Furthermore, in some embodiments, the switch module includes a relay.

[0012] In the above implementation process, relays with advantages such as strong current-carrying capacity, high reliability, simple drive control, and low cost are used as switch modules to improve the overall reliability of the system.

[0013] In a second aspect, an embodiment of the present application provides a control method for an electric vehicle electric drive system as described in the first aspect, comprising: when the electric vehicle is in a normal driving state or in a first DC charging state, controlling the switch module to close; wherein, in the first DC charging state, the maximum voltage of the charging pile is higher than or equal to the voltage of the power battery system.

[0014] In the above implementation process, a control method for the electric vehicle electric drive system is provided when applied to two working conditions: normal driving and ordinary DC charging.

[0015] Furthermore, in some embodiments, it also includes: when the electric vehicle is in a second DC charging state, controlling the switch module to disconnect and sending instructions to the charging pile to make the charging pile output a charging voltage; wherein, in the second DC charging state, the maximum voltage of the charging pile is lower than the voltage of the power battery system; after the charging voltage reaches a preset condition, using a modulated PWM wave to control the high and low voltage side power switch tubes of the three-phase inverter circuit.

[0016] In the above implementation process, a control method for boost charging is provided.

[0017] Furthermore, in some embodiments, it also includes: when the electric vehicle is in the second DC charging state, controlling the switch module to disconnect, and sending instructions to the charging pile to make the charging pile output a charging voltage; wherein, in the second DC charging state, the maximum voltage of the charging pile is lower than the voltage of the power battery system; after the charging voltage reaches a preset condition, controlling the high-voltage side power switch tube of the second half-bridge circuit group to remain turned on, and the low-voltage side power switch tube to remain turned off, and using a modulated PWM wave to control the high and low voltage side power switch tubes of the first half-bridge circuit group.

[0018] In the above implementation process, an optimal control method is provided for boost charging, which reduces the switching frequency of the power switch tube of the second half-bridge circuit group as much as possible, thereby reducing losses. At the same time, under the same charging power, the current flowing through the drive motor is reduced, thereby reducing the heat generation of the drive motor.

[0019] Further, in some embodiments, when the second half-bridge circuit group includes a two-phase half-bridge circuit, controlling the high-voltage side power switch tube of the second half-bridge circuit group to remain turned on includes: controlling the high-voltage side power switch tube of one phase half-bridge circuit of the second half-bridge circuit group to remain turned on.

[0020] In the above implementation process, when the second half-bridge circuit group includes two half-bridge circuits, only the high-side power switch tube of one of the half-bridge circuits can be controlled to remain turned on, thereby further reducing the heating of the drive motor.

[0021] Furthermore, in some embodiments, it also includes: when the electric vehicle is in a third DC charging state, controlling the switch module to disconnect and sending an instruction to the charging pile to make the charging pile output a charging voltage; wherein, in the third DC charging state, the difference between the maximum voltage of the charging pile and the voltage of the power battery system is greater than a preset value; after the charging voltage reaches a preset condition, using a modulated PWM wave to control the high and low voltage side power switch tubes of the three-phase inverter circuit.

[0022] In the above implementation process, a control method is provided for the situation where the power battery voltage is too low, so as to increase the power supply voltage of the charging pile and thus increase the charging power.

[0023] Furthermore, in some embodiments, it also includes: when the electric vehicle is in a third DC charging state, controlling the switch module to disconnect, and sending an instruction to the charging pile to make the charging pile output a charging voltage; wherein, in the third DC charging state, the difference between the maximum voltage of the charging pile and the voltage of the power battery system is greater than a preset value; after the charging voltage reaches a preset condition, controlling the high-voltage side power switch tube of the first half-bridge circuit group to remain turned on, and the low-voltage side power switch tube to remain turned off, and using a modulated PWM wave to control the high and low voltage side power switch tubes of the second half-bridge circuit group.

[0024] In the above implementation process, an optimal control method is provided for the situation where the power battery voltage is too low, which reduces the switching frequency of the power switch tube of the first half-bridge circuit group as much as possible, thereby reducing losses. At the same time, under the same charging power, the current flowing through the drive motor is reduced, thereby reducing the heat generation of the drive motor.

[0025] Other features and advantages disclosed in the present application will be described in the following description, or some features and advantages can be inferred or determined without doubt from the description, or can be learned by implementing the above-mentioned technology disclosed in the present application.

[0026] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A schematic diagram of an electric vehicle power drive system provided in an embodiment of the present application;

[0029] Figure 2 A schematic diagram of an equivalent circuit corresponding to the electric drive system provided in an embodiment of the present application;

[0030] Figure 3 A flow chart of a control method for an electric vehicle electric drive system provided in an embodiment of the present application;

[0031] Figure 4 A schematic diagram of a circuit structure of an electric drive system provided in an embodiment of the present application;

[0032] Figure 5This is a schematic diagram of a circuit structure of another electric drive system according to an embodiment of the present application, in which the three-phase inverter bridge is disconnected at the negative pole;

[0033] Figure 6 This is a schematic diagram of the circuit structure of another electric drive system shown in an embodiment of the present application. In this circuit, two half-bridges of a three-phase inverter bridge are connected to the battery side. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0035] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0036] As described in the background technology, the prior art solution for boosting the output voltage of a DC charging station relies on a dedicated boost converter, which increases the cost of the vehicle. Based on this, the present invention provides an electric drive system for an electric vehicle to address this issue.

[0037] Next, the embodiments of the present application are introduced:

[0038] like Figure 1 As shown, Figure 1 Schematic diagram of an electric vehicle power drive system provided by an embodiment of the present application. The electric vehicle power drive system 11 includes: a power battery system 12, a three-phase inverter circuit 13, a drive motor 14 and a switch module 15, wherein:

[0039] The input end of the three-phase inverter circuit 13 is connected to the power battery system 12, and the output end is connected to the drive motor 14; the three-phase inverter circuit 13 includes a first half-bridge circuit group 131 and a second half-bridge circuit group 132, wherein the first half-bridge circuit group 131 includes a one-phase half-bridge circuit or a two-phase half-bridge circuit; the first half-bridge circuit group 131 and the second half-bridge circuit group 132 are connected through the switch module 15; the positive pole of the first half-bridge circuit group 131 is connected to the positive pole of the power battery system 12, and the negative pole of the first half-bridge circuit group 131 is connected to the negative pole of the power battery system 12; the positive pole of the second half-bridge circuit group 132 is connected to the positive pole of the DC charging port 16, and the negative pole of the second half-bridge circuit group 132 is connected to the negative pole of the DC charging port 16.

[0040] The above-mentioned electric drive system is a system composed of a power battery system and a modified electric drive system, wherein the power battery system provides power to the electric drive system to operate the drive motor in the electric drive system, thereby providing power for the electric vehicle. In some scenarios, it can also be applied to other types of electric equipment, such as electric ships. The principle of the above-mentioned electric drive system is to add a switch module and make certain adjustments to the three-phase inverter circuit of the drive motor to reuse the existing three-phase inverter circuit power switch tube and motor winding inductance to achieve boost charging. Compared with adding a dedicated boost converter, the cost is greatly reduced.

[0041] Specifically, in the aforementioned electric drive system, the power battery system may include power batteries, such as lithium-ion power batteries or nickel-metal hydride batteries. The power battery system can be connected to a DC bus to provide power to loads on the DC bus, such as a motor controller. In addition to the power battery, the power battery system may also include a battery management system, a thermal management system, and structural components. The battery management system is used for intelligent management and maintenance of each battery cell. The thermal management system includes a fan, battery heating and cooling components, and the structural components include mounting components, seals, metal parts, and a housing.

[0042] In the above-mentioned electric drive system, the three-phase inverter circuit is composed of three single-phase inverter circuits, each of which is a one-phase half-bridge circuit, including a high-voltage side power switch tube and a low-voltage side power switch tube. The power switch tube here can be an IGBT (Insulated Gate Bipolar Transistor), or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), a BJT (Bipolar Junction Transistor), and the like. In this embodiment, the three-phase inverter circuit is divided into a first half-bridge circuit group and a second half-bridge circuit group based on the switch module. The first half-bridge circuit group includes a one-phase half-bridge circuit or a two-phase half-bridge circuit. That is, the three half-bridge circuits of the three-phase inverter circuit are divided into two groups, one group includes one half-bridge circuit, and the other group includes two half-bridge circuits.

[0043] Optionally, the three-phase inverter circuit can have at least the following two circuit topologies: In some embodiments, the positive pole of the first half-bridge circuit group and the positive pole of the second half-bridge circuit group are connected via the switch module; the negative pole of the first half-bridge circuit group and the negative pole of the second half-bridge circuit group are directly connected. In other words, the positive poles of the two separate parts of the three-phase inverter circuit can be connected together via the switch module. In other embodiments, the negative pole of the first half-bridge circuit group and the negative pole of the second half-bridge circuit group are connected via the switch module; the positive pole of the first half-bridge circuit group and the positive pole of the second half-bridge circuit group are directly connected. In other words, the negative poles of the two separate parts of the three-phase inverter circuit can be connected together via the switch module, i.e., the three-phase inverter bridge can also be disconnected at the negative pole.

[0044] In the aforementioned electric drive system, the drive motor can be the power source of the electric vehicle and is the component that directly converts electrical energy into mechanical energy. The drive motor can be connected to the three-phase output terminals of a three-phase inverter circuit via an AC cable. The drive motor can be a permanent magnet synchronous motor, a brushless DC motor, or a three-phase asynchronous motor.

[0045] In the above-mentioned electric drive system, the function of the switch module is to switch the presentation form of the three-phase inverter circuit to control the working mode in the three-phase inverter circuit to a certain extent. When the switch module is closed, the first half-bridge circuit group and the second half-bridge circuit group can be combined into a normal three-phase inverter circuit; when the switch module is disconnected, by controlling the power switch tube, the current generated by the drive motor based on the output voltage of the charging pile can be controlled to flow to the connection point of the two power switch tubes of the first half-bridge circuit group. Optionally, the switch module can be a relay, such as an electromagnetic relay, a solid-state relay, etc. A relay is an electrical control device. When the change in the input quantity (excitation quantity) reaches the specified requirement, it is an electrical appliance that causes a predetermined step change in the controlled quantity in the electrical output circuit. It has the advantages of strong current flow capacity, high reliability, simple drive control, and low cost. Of course, in other embodiments, the switch module can also be other types of electronic devices, and this application is not limited to this.

[0046] In the electric drive system of this embodiment, the positive and negative electrodes of the second half-bridge circuit group are respectively connected to the positive and negative electrodes of the DC charging port. The DC charging port is a charging interface for electric vehicles that can be connected to a DC charging station to charge the power battery system. When the output voltage of the DC charging station is lower than the voltage of the power battery system, boost charging can be achieved based on the electric drive system of this embodiment.

[0047] Specifically, taking the example that the second half-bridge circuit group includes a two-phase half-bridge circuit, and the positive electrode of the first half-bridge circuit group and the positive electrode of the second half-bridge circuit group are connected through a switch module, when boost charging, the switch module is disconnected, and the electric drive system at this time can be simplified as follows Figure 2 The equivalent circuit shown in FIG. 1 shows a circuit diagram of a second half-bridge circuit group, wherein the four power switch tubes of the second half-bridge circuit group and the inductance of the drive motor winding can be simplified to switch tubes Q35, Q46 and equivalent inductors (labeled 24, 25 and 26 in the figure), which are represented by Figure 2 As can be seen, the equivalent circuit is a full-bridge circuit with power supplied by the power battery 21 and the charging pile 27 on either side. By controlling the four switches of the full-bridge circuit, the current in the equivalent inductor can be controlled. When the current in the equivalent inductor flows toward the power battery, the power battery is charged; when the current flows away from the power battery, the power battery is discharged. Because the output voltage of the charging pile is lower than the voltage of the power battery during boost charging, switch Q35 can be fully closed and switch Q46 can be fully opened, leaving only switches Q1 and Q2 (labeled 22 and 23 in the figure) to control the current. When switch Q2 is turned on, the charging pile power source forms a loop via switch Q35-equivalent inductor-switch Q2, and the current is converted into magnetic energy in the equivalent inductor. When switch Q1 is turned on, the magnetic energy in the equivalent inductor is converted into electrical energy, forming a loop via switch Q35-equivalent inductor-switch Q1-power battery, completing the boost function. It should be noted that the control method mentioned here is only an example, and the electric drive system can also achieve boost charging based on other control methods; the output power of the charging pile can be controlled by the duty cycle of the PWM wave.

[0048] An embodiment of the present application provides an electric drive system for an electric vehicle. The electric drive system divides the three-phase inverter circuit of the drive motor into a first half-bridge circuit group and a second half-bridge circuit group by adding a switch module. The first half-bridge circuit group is connected to the power battery system, and the second half-bridge circuit group is connected to the DC charging port. In this way, the existing three-phase inverter circuit power switch tubes and motor winding inductors are reused to achieve boost charging, which greatly reduces the cost compared to adding a dedicated boost converter.

[0049] like Figure 3 As shown, Figure 3 : is a flow chart of a control method for an electric vehicle electric drive system provided in an embodiment of the present application. The electric vehicle electric drive system is the electric drive system in any of the aforementioned embodiments. The control method includes:

[0050] In step 301, when the electric vehicle is in a normal driving state or in a first DC charging state, the switch module is controlled to be closed; wherein, in the first DC charging state, the maximum voltage of the charging pile is higher than or equal to the voltage of the power battery system.

[0051] When the vehicle is driving normally, the switch module is closed. At this time, the three-phase inverter circuit as a whole is no different from a normal three-phase inverter. The three-phase inverter circuit controls the drive motor to drive the vehicle. When the vehicle is performing ordinary DC charging, that is, the charging pile voltage is high enough to directly charge the battery, the switch module is closed, and then the entire vehicle can send instructions to the charging pile to make the charging pile charge according to the current battery voltage. The overall charging process is no different from the normal DC fast charging process.

[0052] Some embodiments of the present application also provide a control method for boost charging, which may include: when the electric vehicle is in a second DC charging state, controlling the switch module to disconnect and sending a command to the charging pile to cause the charging pile to output a charging voltage; wherein, in the second DC charging state, the maximum voltage of the charging pile is lower than the voltage of the power battery system; and after the charging voltage reaches a preset condition, using a modulated PWM wave to control the high and low voltage side power switches of the three-phase inverter circuit. That is, when the maximum voltage of the charging pile is lower than the battery voltage, boost charging is required. During boost charging, the switch module is disconnected, and the vehicle sends a command to the charging pile to output a charging voltage. After the charging pile voltage reaches a set requirement, the three-phase inverter bridge controls each switch using a modulated PWM wave to output a voltage to the motor, controlling the drive motor winding to generate current according to the charging power requirement, so that the current of the motor phases connected to the first half-bridge circuit group flows from the drive motor winding to the connection point of the two power switches of the inverter bridge in the first half-bridge circuit group. In this way, boost charging is achieved. It should be noted that the preset condition mentioned here can be a pre-set voltage threshold, which can be set according to the needs of the specific scenario.

[0053] Furthermore, in some other embodiments, the control method may include: when the electric vehicle is in a second DC charging state, controlling the switch module to disconnect and sending a command to the charging pile to cause the charging pile to output a charging voltage; wherein, in the second DC charging state, the maximum voltage of the charging pile is lower than the voltage of the power battery system; after the charging voltage reaches a preset condition, controlling the high-side power switch of the second half-bridge circuit group to remain on and the low-side power switch to remain off, and using a modulated PWM wave to control the high- and low-side power switches of the first half-bridge circuit group. This can be considered a preferred control method for boost charging. In this case, the high-side power switch of the second half-bridge circuit group connected to the DC charging port remains on, while the low-side switch remains off. Only the power switches of the first half-bridge circuit group switch under PWM control and control the charging current. This preferred solution minimizes the switching frequency of the power switches of the second half-bridge circuit group, thereby reducing losses. At the same time, at the same charging power, it reduces the current flowing through the drive motor, thereby reducing drive motor heating.

[0054] Furthermore, when the second half-bridge circuit group includes two half-bridge circuits, the aforementioned control of the high-side power switch of the second half-bridge circuit group to remain conductive may include controlling the high-side power switch of one of the half-bridge circuits of the second half-bridge circuit group to remain conductive. That is, when the second half-bridge circuit group includes two half-bridge circuits, only the high-side power switch of one of the half-bridge circuits may be controlled to remain conductive, thereby further reducing heating of the drive motor.

[0055] During use, electric vehicles may be unable to fully utilize the output power of the charging pile due to low battery voltage. Some embodiments of the present application also provide a control method for "step-down charging." This control method may include: when the electric vehicle is in a third DC charging state, controlling the switch module to disconnect and sending a command to the charging pile to cause the charging pile to output a charging voltage; wherein, in the third DC charging state, the difference between the maximum voltage of the charging pile and the voltage of the power battery system is greater than a preset value; after the charging voltage reaches a preset condition, using a modulated PWM wave to control the high and low voltage side power switches of the three-phase inverter circuit. This control method is basically the same as the control method for boost charging. When the battery voltage is too low, if conventional DC charging is used, the voltage of the charging pile must match the battery voltage. However, when DC charging is performed based on the control method of this embodiment, the charging pile supply voltage can be increased, thereby increasing the charging power. It should be noted that the preset value can be set according to the needs of the specific scenario. For example, in some scenarios, the preset value can be 300V. A certain DC charging pile can output 800V voltage. When the battery voltage is lower than 500V, the control scheme of this embodiment can be adopted to increase the charging power; the final output voltage of the charging pile should not exceed the maximum voltage that the three-phase inverter bridge can withstand.

[0056] Furthermore, in some other embodiments, the control method may include: when the electric vehicle is in a third DC charging state, controlling the switch module to disconnect and sending a command to the charging pile to cause the charging pile to output a charging voltage; wherein, in the third DC charging state, the difference between the maximum voltage of the charging pile and the voltage of the power battery system is greater than a preset value; after the charging voltage reaches a preset condition, controlling the high-side power switch of the first half-bridge circuit group to remain on and the low-side power switch to remain off, and controlling the high- and low-side power switches of the second half-bridge circuit group using a modulated PWM wave. Similarly, this can be considered a preferred control method for "step-down charging," in which the power switch on the high-side of the inverter bridge connected to the battery remains on, while the low-side power switch remains off. Only the other part of the inverter, i.e., the second half-bridge circuit group, controls the motor current under PWM control. This preferred solution minimizes the switching frequency of the power switches of the first half-bridge circuit group, thereby reducing losses. At the same time, at the same charging power, it reduces the current flowing through the drive motor, thereby reducing heat generation in the drive motor. In addition, when the second half-bridge circuit group includes a two-phase half-bridge circuit, the PWM wave can be used to control the switching action of all four power switch tubes, or only the switching action of two power switch tubes on one of the inverter bridges can be controlled. This application does not impose any restrictions on this.

[0057] In order to explain the solution of this application in more detail, a specific embodiment is introduced below:

[0058] like Figure 4 As shown, Figure 4 This is a schematic diagram of the circuit structure of an electric drive system provided in an embodiment of the present application. The electric drive system 41 includes a power battery 42, a three-phase inverter bridge 43, a relay Ki44 and a drive motor 45; a DC charging pile 47 can charge the power battery 42 through a DC charging port 46. Compared with the conventional electric vehicle electrical topology, the difference of this embodiment is at least that: the three half-bridge circuits of the three-phase inverter bridge 43 are divided into two groups, one group includes a one-phase half-bridge circuit, that is, the Q1Q2 half-bridge circuit composed of power switch tubes Q1 (marked as 431 in the figure) and Q2 (marked as 432 in the figure), and the other group includes a two-phase half-bridge circuit, that is, the Q3Q4 half-bridge circuit composed of power switch tubes Q3 (marked as 433 in the figure) and Q4 (marked as 434 in the figure) and the Q5Q6 half-bridge circuit composed of power switch tubes Q5 (marked as 435 in the figure) and Q6 (marked as 436 in the figure); the positive pole of one group of half-bridge circuits is directly connected to the positive pole of the power battery 42, and the positive pole of the other group of half-bridge circuits is connected to the positive pole of the DC charging port 46; the positive poles of the two separated parts of the three-phase inverter bridge 43 are connected together through relay Ki44.

[0059] For the electric drive system of the embodiment of the present application, the following control method is adopted:

[0060] First, for normal vehicle driving conditions: close relay Ki, and the three-phase inverter bridge controls the drive motor to drive the vehicle. The overall operation is no different from a normal three-phase inverter.

[0061] Second, for ordinary DC charging conditions: when the voltage of the charging pile is high enough to directly charge the battery, the relay Ki is closed, and then the vehicle sends a command to the charging pile to charge according to the current voltage of the power battery. The overall charging process is no different from the normal DC fast charging process;

[0062] Third, for the working condition of boost charging: when the maximum voltage of the charging pile is lower than the battery voltage, boost charging is required. The control process includes:

[0063] S401, disconnect relay Ki;

[0064] S402: The vehicle sends a command to the charging pile to make the charging pile output a charging voltage;

[0065] S403: After the charging pile voltage reaches the set requirement, the three-phase inverter bridge controls the output voltage of each power switch tube to the drive motor through the modulated PWM wave, controls the drive motor winding to generate current according to the charging power requirement, and makes the current of the motor phase connected to Q1Q2 flow from the drive motor winding to the connection point of Q1Q2;

[0066] Preferably, at this time, the power switches Q3 and Q5 on the high-voltage side of the inverter bridge connected to the charging port remain on, while the power switches Q4 and Q6 on the low-voltage side remain off. Only Q1 and Q2 perform switching actions under PWM wave control and control the charging current.

[0067] S404: After charging is completed, the three-phase inverter bridge stops working;

[0068] Through the above process, the charging pile with lower output voltage can effectively charge the power battery;

[0069] Fourth, for the working condition of step-down charging: During the use of electric vehicles, there is often a situation where the output power of the charging pile cannot be fully utilized because the battery voltage is too low. For example, a DC charging pile can output 800V voltage and 200A current, and the maximum charging power of the charging pile is 160kW. If the battery voltage is only 350V, then when using conventional DC charging, the voltage of the charging pile must match the battery voltage. Therefore, the charging pile can only output 350V. Even at the maximum current output, the charging pile can only provide 350V*200A=70kW charging power, which is far less than the maximum capacity of 160kW. At this time, the charging power can be increased through the following control process:

[0070] S411, disconnect relay Ki;

[0071] S412: The vehicle sends a command to the charging pile to make it output a charging voltage. At this time, the charging pile output voltage is greater than the battery voltage, but not higher than the maximum voltage that the inverter can withstand, such as 500V.

[0072] S413: After the charging pile voltage reaches the set requirement, the three-phase inverter bridge controls the output voltage of each power switch tube to the drive motor through the modulated PWM wave, controls the drive motor winding to generate current according to the charging power requirement, and makes the current of the motor phase connected to Q1Q2 flow from the drive motor winding to the connection point of Q1Q2;

[0073] Preferably, at this time, the power switch tube Q1 on the high-voltage side of the inverter bridge connected to the battery remains turned on, while the power switch tube Q2 on the low-voltage side remains turned off, and only the other part of the inverter controls the drive motor current under PWM wave control (only Q3Q4, or only Q5Q6, or all Q3Q4Q5Q6 are switched);

[0074] S414: After charging is completed, the three-phase inverter bridge stops working;

[0075] Through the above process, the charging pile power supply voltage can be increased to 500V, at which time the maximum power can reach 500V*200A=100kW, significantly improving the charging power.

[0076] In addition, this application Figure 4 Based on the circuit shown, the following variations are also provided (for convenience, only the changed parts of the circuit are numbered in the schematic diagrams of the following variations, and the rest are not numbered):

[0077] Variation 1: Using the equivalent circuit topology, the three-phase inverter bridge can be disconnected at the negative pole, such as Figure 5 As shown, Figure 5 Schematic diagram of the circuit structure of another electric drive system shown in an embodiment of the present application; wherein the negative electrodes of the two separated parts of the three-phase inverter bridge are connected together through the relay Ki51;

[0078] Variation 2: The three-phase inverter bridge can select two half-bridges to connect to the battery side and the other half-bridge to connect to the DC charging port, such as Figure 6 As shown, Figure 6 Schematic diagram of the circuit structure of another electric drive system shown in an embodiment of the present application; wherein the positive poles of the two separated parts of the three-phase inverter bridge are connected together through the relay Ki61.

[0079] The above-mentioned changes can provide a more flexible structural arrangement. The specific circuit selection can be based on comprehensive considerations of factors such as the loss and heat generation of the electric drive system under conditions such as boost charging and buck charging.

[0080] The foregoing is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures.

[0081] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0082] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

Claims

1. An electric vehicle electric drive system, characterized in that: It includes a power battery system, a three-phase inverter circuit, a drive motor and a switch module, including: The input end of the three-phase inverter circuit is connected to the power battery system, and the output end is connected to the drive motor; the three-phase inverter circuit includes a first half-bridge circuit group and a second half-bridge circuit group, wherein the first half-bridge circuit group includes a one-phase half-bridge circuit or a two-phase half-bridge circuit; the first half-bridge circuit group and the second half-bridge circuit group are connected via the switch module; the positive electrode of the first half-bridge circuit group is connected to the positive electrode of the power battery system, and the negative electrode of the first half-bridge circuit group is connected to the negative electrode of the power battery system; the positive electrode of the second half-bridge circuit group is connected to the positive electrode of the DC charging port, and the negative electrode of the second half-bridge circuit group is connected to the negative electrode of the DC charging port; when the electric vehicle is in a normal driving state or in a first DC charging state, the switch module is closed; when the electric vehicle is in a third DC charging state, the switch module is disconnected; wherein, in the first DC charging state, the maximum voltage of the charging pile is higher than or equal to the voltage of the power battery system; in the third DC charging state, the difference between the maximum voltage of the charging pile and the voltage of the power battery system is greater than a preset value; The drive motor includes a permanent magnet synchronous motor; the power switch tube in the three-phase inverter circuit adopts any one of IGBT, MOSFET and BJT.

2. The electric vehicle electric drive system according to claim 1, characterized in that: The positive electrode of the first half-bridge circuit group and the positive electrode of the second half-bridge circuit group are connected through the switch module; the negative electrode of the first half-bridge circuit group and the negative electrode of the second half-bridge circuit group are directly connected.

3. The electric vehicle power drive system according to claim 1, characterized in that: The cathode of the first half-bridge circuit group and the cathode of the second half-bridge circuit group are connected via the switch module; the anode of the first half-bridge circuit group and the anode of the second half-bridge circuit group are directly connected.

4. The electric vehicle electric drive system according to claim 1, characterized in that: The switch module includes a relay.

5. A control method for an electric vehicle electric drive system according to any one of claims 1 to 4, characterized in that: include: When the electric vehicle is in a normal driving state or in a first DC charging state, the switch module is controlled to be closed; wherein, in the first DC charging state, the maximum voltage of the charging pile is higher than or equal to the voltage of the power battery system; When the electric vehicle is in a third DC charging state, the switch module is controlled to be disconnected, and an instruction is sent to the charging pile to enable the charging pile to output a charging voltage; wherein, in the third DC charging state, the difference between the maximum voltage of the charging pile and the voltage of the power battery system is greater than a preset value; After the charging voltage reaches a preset condition, the modulated PWM wave is used to control the high and low voltage side power switches of the three-phase inverter circuit, or the high voltage side power switch of the first half-bridge circuit group is controlled to remain turned on and the low voltage side power switch is controlled to remain turned off, and the modulated PWM wave is used to control the high and low voltage side power switches of the second half-bridge circuit group.

6. The control method according to claim 5, characterized in that: Also includes: When the electric vehicle is in a second DC charging state, the switch module is controlled to be disconnected, and an instruction is sent to the charging pile to enable the charging pile to output a charging voltage; wherein, in the second DC charging state, the maximum voltage of the charging pile is lower than the voltage of the power battery system; After the charging voltage reaches a preset condition, the modulated PWM wave is used to control the high and low voltage side power switches of the three-phase inverter circuit.

7. The control method according to claim 5, characterized in that: Also includes: When the electric vehicle is in a second DC charging state, the switch module is controlled to be disconnected, and an instruction is sent to the charging pile to enable the charging pile to output a charging voltage; wherein, in the second DC charging state, the maximum voltage of the charging pile is lower than the voltage of the power battery system; After the charging voltage reaches a preset condition, the high-voltage side power switch tube of the second half-bridge circuit group is controlled to remain turned on, and the low-voltage side power switch tube is controlled to remain turned off, and the modulated PWM wave is used to control the high-voltage and low-voltage side power switch tubes of the first half-bridge circuit group.

8. The control method according to claim 7, characterized in that: When the second half-bridge circuit group includes a two-phase half-bridge circuit, controlling the high-side power switch tube of the second half-bridge circuit group to remain turned on includes: The high-side power switch tube of one phase half-bridge circuit of the second half-bridge circuit group is controlled to remain turned on.

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