A control method, device and system of an electric drive system of an electric vehicle

Abstract

This invention discloses a control method, device, and system for an electric drive system of an electric vehicle. The electric drive system includes a motor and a T-type three-level circuit. The control method includes: determining a target control mode for the T-type three-level circuit based on target parameters of the motor; determining the level control states of the target control mode according to the target parameters and the target control mode; wherein, when the target control mode is a two-level control mode, the level control states of the target control mode include a high-level control state and a low-level control state; when the target control mode is a three-level control mode, the level control states of the target control mode include a P-level control state, an O-level control state, and an N-level control state; and controlling the conduction state of each transistor in the T-type three-level circuit according to the level control states of the target control mode, so that the T-type three-level circuit drives the motor to achieve the target parameters. The technical solution of this invention improves the performance and system efficiency of the electric drive system.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a control method, device and system for an electric drive system of an electric vehicle. Background Technology

[0002] In the electric drive systems of electric vehicles, two-level circuit structures and T-type three-level circuit structures are two widely used topologies in the industry. The two-level circuit structure has two transistors per phase arm, enabling it to output two voltage levels. Its circuit structure is simple, but the output voltage drop is relatively large, resulting in higher harmonic content in the three-phase current. The T-type three-level circuit structure has four transistors per phase arm, enabling it to output three voltage levels. Its output voltage drop is smaller, reducing the harmonic content in the three-phase current.

[0003] The system efficiency of an electric drive system refers to the ratio of output power to input power. Under high-speed, high-modulation conditions, the switching losses of a two-level circuit structure are too high, resulting in low motor system efficiency. Under low-speed, high-torque conditions, the conduction losses of multiple transistors in a T-type three-level circuit structure are too high, and fluctuations in the DC bus midpoint voltage affect the modulation of the three-phase current, causing current harmonics and further reducing motor system efficiency. Therefore, neither the two-level nor the T-type three-level circuit structure can achieve optimal system efficiency across all operating conditions, impacting the overall efficiency of the electric drive system and the driving range of electric vehicles. Summary of the Invention

[0004] This invention provides a control method, device, and system for an electric drive system of an electric vehicle, which improves the performance and system efficiency of the electric drive system.

[0005] In a first aspect, the present invention provides a control method for an electric drive system of an electric vehicle, the electric drive system comprising a motor and a T-type three-level circuit; the control method comprising: Based on the target parameters of the motor, the target control mode of the T-type three-level circuit is determined; wherein, the target control mode includes a two-level control mode and a three-level control mode; Based on the target parameters and the target control mode, the level control state of the target control mode is determined; wherein, when the target control mode is the two-level control mode, the level control state of the target control mode includes a high-level control state and a low-level control state; when the target control mode is the three-level control mode, the level control state of the target control mode includes a P-level control state, an O-level control state, and an N-level control state. According to the level control state of the target control mode, the conduction state of each transistor in the T-type three-level circuit is controlled so that the T-type three-level circuit drives the motor to achieve the target parameters.

[0006] Optionally, the target parameters include target torque and / or target speed; based on the target parameters of the motor, the target control mode of the T-type three-level circuit is determined, including: Based on the target torque and / or target speed of the motor, the target control mode of the T-type three-level circuit is determined, and under the target control mode, the parameters of the electric drive system meet preset conditions.

[0007] Optionally, before controlling the conduction state of each transistor in the T-type three-level circuit according to the level control state of the target control mode, the method further includes: Obtain the current control mode of the T-type three-level circuit; When the current control mode differs from the target control mode, an intermediate control state is determined; Based on the intermediate control state, the conduction state of each transistor in the T-type three-level circuit is controlled; The T-type three-level circuit includes a first transistor, a second transistor, a third transistor, and a fourth transistor. The first transistor and the fourth transistor are connected in series between the positive terminal and the negative terminal of the DC bus, and the second transistor and the third transistor are connected in series between the midpoint of the DC bus and the output terminal. The intermediate control states include a P intermediate state where the second transistor is turned on, an N intermediate state where the third transistor is turned on, and an OFF intermediate state where all transistors are turned off.

[0008] Optionally, when the current control mode differs from the target control mode, an intermediate control state is determined, including: When either the second transistor or the third transistor is not turned on in both the level control state of the current control mode and the level control state of the target control state, the intermediate control state is determined to be the OFF intermediate state. When the first transistor is not turned on in both the level control state of the current control mode and the level control state of the target control state, the intermediate control state is determined to be the N intermediate state. When the fourth transistor is not turned on in both the current control mode's level control state and the target control state's level control state, the intermediate control state is determined to be the P intermediate state.

[0009] Optionally, when the transistor that is not turned on in both the current control mode's level control state and the target control state's level control state is the second transistor or the third transistor, the intermediate control state is determined to be the OFF intermediate state, including: When the level control state of the current control mode and the level control state of the target control state include the high level control state and / or the N level control state, the intermediate control state is determined to be the OFF intermediate state and the N intermediate state. When the level control state of the current control mode and the level control state of the target control state include the low level control state and / or the P level control state, the intermediate control state is determined to be the OFF intermediate state and the P intermediate state.

[0010] Optionally, based on the intermediate control state, the conduction state of each transistor in the T-type three-level circuit is controlled, including: When the current control mode's level control state is the high-level control state and the target control state's level control state is the N-level control state, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the OFF intermediate state and the N intermediate state; conversely, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the N intermediate state and the OFF intermediate state. When the current control mode's level control state is the low level control state and the target control state's level control state is the P level control state, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the OFF intermediate state and the P intermediate state; conversely, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the P intermediate state and the OFF intermediate state.

[0011] Optionally, when the first transistor is not turned on in both the level control state of the current control mode and the level control state of the target control state, the intermediate control state is determined to be the N intermediate states, including: When the level control state of the current control mode and the level control state of the target control state include the low level control state and / or the 0 level control state, the intermediate control state is determined to be the N level control state and the N intermediate state; Based on the intermediate control state, the conduction state of each transistor in the T-type three-level circuit is controlled, including: When the current control mode's level control state is the low level control state and the target control state's level control state is the 0 level control state, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the N level control state and the N intermediate state; conversely, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the N intermediate state and the N level control state.

[0012] Optionally, when the fourth transistor is not turned on in both the level control state of the current control mode and the level control state of the target control state, the intermediate control state is determined to be the P intermediate state, including: When the level control state of the current control mode and the level control state of the target control state include the high level control state and / or the 0 level control state, the intermediate control state is determined to be the P level control state and the P intermediate state; Based on the intermediate control state, the conduction state of each transistor in the T-type three-level circuit is controlled, including: When the current control mode's level control state is the high-level control state and the target control state's level control state is the 0-level control state, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the P-level control state and the P intermediate state; conversely, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the P intermediate state and the P-level control state.

[0013] Secondly, the present invention provides a control device for an electric drive system of an electric vehicle, the electric drive system including a motor and a T-type three-level circuit; the control device includes: The mode determination module is used to determine the target control mode of the T-type three-level circuit based on the target parameters of the motor; wherein, the target control mode includes a two-level control mode and a three-level control mode; The state determination module is used to determine the level control state of the target control mode based on the target parameters and the target control mode; wherein, when the target control mode is the two-level control mode, the level control state of the target control mode includes a high-level control state and a low-level control state; when the target control mode is the three-level control mode, the level control state of the target control mode includes a P-level control state, an O-level control state, and an N-level control state. The state control module is used to control the conduction state of each transistor in the T-type three-level circuit according to the level control state of the target control mode, so that the T-type three-level circuit drives the motor to achieve the target parameters.

[0014] Thirdly, the present invention provides a control system for an electric drive system of an electric vehicle, the control system of which includes the control device for the electric drive system described in the second aspect, for executing the control method for the electric drive system described in the first aspect.

[0015] The technical solution of this invention enables a two-level or three-level control mode through a T-type three-level circuit. Based on the target parameters of the motor, the target control mode of the T-type three-level circuit is determined to be either a two-level or three-level control mode. Furthermore, by determining the level control state of the target control mode according to the target parameters and the target control mode, and then controlling the conduction state of each transistor in the T-type three-level circuit according to the target control mode and its level control state, the T-type three-level circuit drives the motor to achieve the target parameters. In this way, a suitable control mode can be selected according to the operating state of the motor, which can reduce losses and improve the performance and system efficiency of the electric drive system. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a single-phase structure of a T-type three-level circuit provided in an embodiment of the present invention; Figure 2 This is a flowchart illustrating a control method for an electric drive system of an electric vehicle according to Embodiment 1 of the present invention. Figure 3 This is a flowchart illustrating a control method for an electric drive system of an electric vehicle according to Embodiment 2 of the present invention. Figure 4 This is a flowchart illustrating a control method for an electric drive system of an electric vehicle according to Embodiment 3 of the present invention. Figure 5 This is a schematic diagram of the structure of a control device for an electric drive system of an electric vehicle provided in an embodiment of the present invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0018] The terminology used in the embodiments of this invention is for the purpose of describing specific embodiments only and is not intended to limit the invention. It should be noted that directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this invention. Furthermore, in the context, it should be understood that when referring to an element being formed "on" or "below" another element, it can be formed not only directly on or below the other element, but also indirectly on or below it through intermediate elements. The terms "first," "second," etc., are used for descriptive purposes only and do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] The term "comprising" and its variations as used in this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment".

[0020] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish the corresponding contents and are not used to limit the order or interdependence.

[0021] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0022] The T-type three-level circuit is a high-performance three-phase inverter topology. It consists of phases a, b, and c. Figure 1 This is a schematic diagram of a single-phase structure of a T-type three-level circuit provided in an embodiment of the present invention, as shown below. Figure 1As shown, each phase T-type three-level circuit includes four transistors and two capacitors. The first transistor T1 and the fourth transistor T4 are connected in series between the positive terminal DCP and the negative terminal DCN of the DC bus. The second transistor T2 and the third transistor T3 are connected in series between the midpoint DCO of the DC bus and the output terminal PH. The first capacitor C1 and the second capacitor C2 are connected in series between the positive terminal DCP and the negative terminal DCN of the DC bus. In a T-type three-level circuit, the switching state of each transistor determines the output voltage of the output terminal PH. When the first transistor T1 and the second transistor T2 are on, and the third transistor T3 and the fourth transistor T4 are off, the output voltage of the output terminal PH relative to the DC bus midpoint DCO is positive level Udc / 2. When the second transistor T2 and the third transistor T3 are on, and the first transistor T1 and the fourth transistor T4 are off, the output voltage of the output terminal PH relative to the DC bus midpoint DCO is 0. When the third transistor T3 and the fourth transistor T4 are on, and the first transistor T1 and the second transistor T2 are off, the output voltage of the output terminal PH relative to the DC bus midpoint DCO is negative level -Udc / 2. Therefore, when the T-type three-level circuit switches levels, the output voltage drop at the output terminal PH is Udc / 2, which reduces switching losses, decreases harmonic content and system losses in the three-phase current, and improves system efficiency. However, under conditions such as low speed and high current or high speed and high modulation, the T-type three-level circuit requires more transistors, which increases the conduction losses of the transistors. The fluctuation of the DC bus midpoint voltage affects the modulation of the three-phase current, causing current harmonics, which in turn leads to the system efficiency of the T-type three-level circuit being lower than that of the two-level circuit.

[0023] Example 1 Figure 2 This is a flowchart illustrating a control method for an electric drive system of an electric vehicle according to Embodiment 1 of the present invention. This embodiment can be used to control the electric drive system of an electric vehicle, which includes a motor and a T-type three-level circuit. The method can be executed by a control device for the electric drive system. This control method for the electric drive system can be implemented by software and / or hardware, and is generally integrated into the control system of the electric drive system provided in this embodiment of the present invention. Figure 2 As shown, the control method of the electric drive system includes: S110. Based on the target parameters of the motor, determine the target control mode of the T-type three-level circuit.

[0024] The target parameters of the motor can include torque and speed. The target control mode can refer to the optimal control mode of the T-type three-level circuit or the control mode of the next stage of the T-type three-level circuit. Target control modes include two-level control mode and three-level control mode. Two-level control mode refers to the control mode in the T-type three-level circuit where the second transistor T2 and the third transistor T3 are simultaneously turned off, and the first transistor T1 or the fourth transistor T4 is turned on. Three-level control mode refers to the control mode in the T-type three-level circuit where the second transistor T2 and / or the third transistor T3 are turned on. Therefore, by controlling the conduction state of each transistor in the T-type three-level circuit, a two-level control mode or a three-level control mode can be implemented based on the T-type three-level circuit, and a suitable control mode can be selected as the target control mode of the T-type three-level circuit according to the target parameters of the motor.

[0025] In an optional embodiment, the target parameters include target torque and / or target speed; based on the target parameters of the motor, a target control mode for the T-type three-level circuit is determined, including: based on the target torque and / or target speed of the motor, the target control mode for the T-type three-level circuit is determined, and under the target control mode, the parameters of the electric drive system meet preset conditions.

[0026] The parameters of the electric drive system include, but are not limited to, motor torque, motor speed, system efficiency, and system losses.

[0027] For example, the target parameters of the motor and the target control mode of the T-type three-level circuit can be obtained through experiments, experience, and simulation analysis, and a table or mapping relationship can be obtained to determine the target control mode of the T-type three-level circuit. Alternatively, the target control mode of the T-type three-level circuit can be determined by judging the relationship between the target torque and the torque threshold, and the relationship between the target speed and the speed threshold. The specific settings can be set according to actual needs, and the embodiments of the present invention do not impose specific limitations on this. Table 1 below is a table showing the relationship between torque, speed, and the target control mode of the T-type three-level circuit provided by an embodiment of the present invention. As shown in Table 1, a value of 0 indicates that the target control mode of the T-type three-level circuit is a two-level control mode, and a value of 1 indicates that the target control mode of the T-type three-level circuit is a three-level control mode. Blank spaces indicate that the torque and speed combination exceeds the motor's inherent operating characteristics and is not within the motor's normal operating range. After determining the target speed and target torque, the target control mode of the T-type three-level circuit can be determined by referring to the table. The motor system efficiency under the target control mode is greater than that under the non-target control mode, and the motor system losses under the target control mode are less than those under the non-target control mode. Therefore, under the target control mode, the parameters of the electric drive system meet the preset conditions, improving the performance and efficiency of the electric drive system.

[0028] S120. Determine the level control state of the target control mode based on the target parameters and the target control mode.

[0029] Table 2 below shows the relationship between the conduction state and the level control state of each transistor in a two-level control mode provided by an embodiment of the present invention. As shown in Table 2, when the target control mode is a two-level control mode, the level control states of the target control mode include a high-level control state and a low-level control state. For example, when the first transistor T1 is turned on and the second transistor T2, the third transistor T3, and the fourth transistor T4 are all turned off, the output voltage of the output terminal PH relative to the DC bus midpoint DCO is Udc / 2, and the level control state is a high-level control state; when the first transistor T1, the second transistor T2, and the third transistor T3 are all turned off and the fourth transistor is turned on, the output voltage of the output terminal PH relative to the DC bus midpoint DCO is -Udc / 2, and the level control state is a low-level control state.

[0030] Table 3 below shows the relationship between the conduction state and the level control state of each transistor in a three-level control mode provided by an embodiment of the present invention. As shown in Table 3, when the target control mode is a three-level control mode, the level control states of the target control mode include P-level control state, O-level control state, and N-level control state. For example, when the first transistor T1 and the second transistor T2 are turned on, and the third transistor T3 and the fourth transistor T4 are turned off, the output voltage of the output terminal PH relative to the DC bus midpoint DCO is Udc / 2, and the level control state is P-level control state; when the second transistor T2 and the third transistor T3 are turned on, and the first transistor T1 and the fourth transistor T4 are turned off, the output voltage of the output terminal PH relative to the DC bus midpoint DCO is 0, and the level control state is O-level control state; when the third transistor T3 and the fourth transistor T4 are turned on, and the first transistor T1 and the second transistor T2 are turned off, the output voltage of the output terminal PH relative to the DC bus midpoint DCO is -Udc / 2, and the level control state is N-level control state.

[0031] Specifically, after determining the target control mode, the level control state of the target control mode can be determined based on the SVPWM modulation calculation results. First, the d-axis voltage and q-axis voltage of the motor are input to the SVPWM modulation module to calculate the duty cycle command of the three-phase windings. If the target control mode is a two-level control mode, the timing sequence of the high-level control state and the low-level control state is allocated based on the duty cycle command. If the target control mode is a three-level control mode, the timing sequence of the P-level control state, the O-level control state, and the N-level control state is allocated based on the duty cycle command. When switching between the two-level control mode and the three-level control mode, the target level state of the current pulse width modulation cycle needs to be determined based on the actual output level state of the previous pulse width modulation cycle.

[0032] S130. According to the level control state of the target control mode, control the conduction state of each transistor in the T-type three-level circuit so that the T-type three-level circuit drives the motor to achieve the target parameters.

[0033] Specifically, after determining the level control state of the target control mode, the conduction state of each transistor in the T-type three-level circuit can be controlled according to Tables 2 and 3 above, so that the T-type three-level circuit drives the motor to achieve the target parameters. Controlling the working state of the T-type three-level circuit based on the target control mode and its level control state is beneficial to reducing system losses and improving the performance and efficiency of the electric drive system.

[0034] This embodiment utilizes a T-type three-level circuit to achieve either a two-level or three-level control mode. Based on the target parameters of the motor, the target control mode of the T-type three-level circuit is determined to be either a two-level or three-level control mode. Furthermore, by determining the level control state of the target control mode according to the target parameters and the target control mode, the conduction state of each transistor in the T-type three-level circuit is controlled according to the target control mode and its level control state, so that the T-type three-level circuit drives the motor to achieve the target parameters. In this way, a suitable control mode can be selected according to the operating state of the motor, which can reduce losses and improve the performance and system efficiency of the electric drive system.

[0035] Example 2 Figure 3 This is a flowchart illustrating a control method for an electric drive system of an electric vehicle according to Embodiment 2 of the present invention. Based on the above embodiments, this embodiment provides a detailed description of the intermediate control states, such as... Figure 3 As shown, the control method of this electric drive system includes: S210. Based on the target parameters of the motor, determine the target control mode of the T-type three-level circuit.

[0036] S220. Determine the level control state of the target control mode based on the target parameters and the target control mode.

[0037] S230: Obtain the current control mode of the T-type three-level circuit.

[0038] The current control mode can be the default control mode of the T-type three-level circuit or the control mode of the previous stage.

[0039] S240. When the current control mode is different from the target control mode, determine the intermediate control state.

[0040] Specifically, if the current control mode is the same as the target control mode, it means that the system efficiency is the highest at this time, and there is no need to switch the control mode. The T-type three-level circuit operates in the current control mode. If the current control mode is different from the target control mode, it is necessary to switch the control mode by changing the conduction state of each transistor. Since changing the conduction state of multiple transistors at the same time may cause current fluctuations in the T-type three-level circuit, which may lead to short circuit risk, it is necessary to determine an intermediate control state to avoid current fluctuations.

[0041] It should be noted that if the same conducting transistor exists in both the two-level control mode and the three-level control mode, then there is no need to determine an intermediate control state. For example, if the current control mode is a two-level control mode with a high-level control state, and the target control mode is a three-level control mode with a P-level control state, then the first transistor T1 is always conducting. Only the second transistor T2 needs to be switched from the off state to the on state; therefore, there is no need to determine an intermediate control state. Conversely, if the current control mode is a three-level control mode with a P-level control state, and the target control mode is a two-level control mode with a high-level control state, then the first transistor T1 is always conducting. Only the second transistor T2 needs to be switched from the on state to the off state. Therefore, there is no need to determine the intermediate control state. When the current control mode is a two-level control mode with a low-level control state, and the target control mode is a three-level control mode with an N-level control state, it is only necessary to switch the third transistor T3 from the off state to the on state, so there is no need to determine the intermediate control state. Conversely, when the current control mode is a three-level control mode with an N-level control state, and the target control mode is a two-level control mode with a low-level control state, it is only necessary to switch the third transistor T3 from the on state to the off state, so there is no need to determine the intermediate control state.

[0042] S250: Control the conduction state of each transistor in the T-type three-level circuit according to the intermediate control state.

[0043] Table 4 below shows the relationship between the conduction state and intermediate control state of each transistor in a T-type three-level circuit provided by an embodiment of the present invention. As shown in Table 4, the intermediate control states include the P intermediate state where the second transistor T2 is on and the first transistor T1, the third transistor T3, and the fourth transistor T4 are all off; the N intermediate state where the third transistor T3 is on and the first transistor T1, the second transistor T2, and the fourth transistor T4 are all off; and the OFF intermediate state where all transistors are off. The intermediate control states may also include at least some of the control states among the high-level control state, low-level control state, P-level control state, O-level control state, and N-level control state. This embodiment of the invention does not limit this.

[0044] Specifically, in the T-type three-level circuit, the first transistor T1 and the fourth transistor T4 cannot be turned on simultaneously to avoid current flowing directly from the positive terminal DCP of the DC bus to the negative terminal DCN of the DC bus, causing a short circuit; the first transistor T1 and the third transistor T3 cannot be turned on simultaneously to avoid current flowing through the body diodes of the first transistor T1, the third transistor T3, and the second transistor T2, causing a short circuit in the first capacitor C1; the second transistor T2 and the fourth transistor T4 cannot be turned on simultaneously to avoid current flowing through the body diodes of the second transistor T2, the third transistor T3, and the fourth transistor T4, causing a short circuit in the second capacitor C2. By setting intermediate control states, the short-circuit risk of the T-type three-level circuit can be effectively avoided, the smoothness of level control state switching can be improved, and the current fluctuation during the switching of the conduction states of each transistor can be significantly reduced.

[0045] S260. According to the level control state of the target control mode, control the conduction state of each transistor in the T-type three-level circuit so that the T-type three-level circuit drives the motor to achieve the target parameters.

[0046] This embodiment obtains the current control mode of the T-type three-level circuit, and determines the intermediate control state when the current control mode is different from the target control mode. Then, based on the intermediate control state, it controls the conduction state of each transistor in the T-type three-level circuit. By setting the intermediate control state, the short-circuit risk of the T-type three-level circuit can be effectively avoided, the smoothness of the level control state switching can be improved, and the current fluctuation during the conduction state switching of each transistor can be significantly reduced.

[0047] Example 3 Figure 4 This is a flowchart illustrating a control method for an electric drive system of an electric vehicle according to Embodiment 3 of the present invention. Based on the above embodiments, this embodiment provides a detailed explanation of the method for determining intermediate control states, such as... Figure 4 As shown, the control method of this electric drive system includes: S310. Based on the target parameters of the motor, determine the target control mode of the T-type three-level circuit.

[0048] S320. Determine the level control state of the target control mode based on the target parameters and the target control mode.

[0049] S330: Obtain the current control mode of the T-type three-level circuit.

[0050] S340. When the second or third transistor is not turned on in both the current control mode's level control state and the target control state's level control state, the intermediate control state is determined to be the OFF intermediate state.

[0051] Specifically, when the second transistor T2 or the third transistor T3 is not conducting in both the current control mode level control state and the target control state level control state, the first transistor T1 and the fourth transistor T4 are conducting in both the current control mode level control state and the target control state level control state, respectively. In order to avoid the first transistor T1 and the fourth transistor T4 conducting at the same time, the intermediate control state can be determined to be the OFF intermediate state. By setting the OFF intermediate state where all transistors are off, the short circuit risk of the T-type three-level circuit can be effectively avoided.

[0052] In an optional embodiment, when the transistor that is not turned on in both the current control mode level control state and the target control state level control state is the second transistor or the third transistor, determining the intermediate control state as the OFF intermediate state includes: determining the intermediate control state as the OFF intermediate state and the N intermediate state when the current control mode level control state and the target control state level control state level control state include the high level control state and / or the N level control state; and determining the intermediate control state as the OFF intermediate state and the P intermediate state when the current control mode level control state and the target control state level control state level control state include the low level control state and / or the P level control state.

[0053] Based on the above embodiments, the conduction state of each transistor in the T-type three-level circuit is controlled according to the intermediate control state, including: when the level control state of the current control mode is a high-level control state and the level control state of the target control state is an N-level control state, the conduction state of each transistor in the T-type three-level circuit is controlled successively according to the OFF intermediate state and the N intermediate state; otherwise, the conduction state of each transistor in the T-type three-level circuit is controlled successively according to the N intermediate state and the OFF intermediate state; when the level control state of the current control mode is a low-level control state and the level control state of the target control state is a P-level control state, the conduction state of each transistor in the T-type three-level circuit is controlled successively according to the OFF intermediate state and the P intermediate state; otherwise, the conduction state of each transistor in the T-type three-level circuit is controlled successively according to the P intermediate state and the OFF intermediate state.

[0054] Specifically, when the current control mode's level control state is high and the target control state's level control state is N-level control, the intermediate control state is first determined to be OFF, causing the first transistor T1 to switch from the ON state to the OFF state. Then, the intermediate control state is determined to be N-level, causing the third transistor T3 to switch from the OFF state to the ON state. Finally, the control state is switched to N-level, causing the fourth transistor T4 to switch from the OFF state to the ON state. Conversely, when the current control mode's level control state is N-level and the target control state's level control state is high, the intermediate control state is first determined to be N-level, causing the fourth transistor T4 to switch from the ON state to the OFF state. Then, the intermediate control state is determined to be OFF, causing the third transistor T3 to switch from the ON state to the OFF state. Finally, the control state is switched to high, causing the first transistor T1 to switch from the OFF state to the ON state.

[0055] When the current control mode's level control state is low and the target control state's level control state is P, the intermediate control state is first determined to be OFF, causing the fourth transistor T4 to switch from the ON state to the OFF state. Then, the intermediate control state is determined to be P, causing the second transistor T2 to switch from the OFF state to the ON state. Finally, the control state is switched to P, causing the first transistor T1 to switch from the OFF state to the ON state. Conversely, when the current control mode's level control state is P and the target control state's level control state is low, the intermediate control state is first determined to be P, causing the first transistor T1 to switch from the ON state to the OFF state. Then, the intermediate control state is determined to be OFF, causing the second transistor T2 to switch from the ON state to the OFF state. Finally, the control state is switched to low, causing the fourth transistor T4 to switch from the OFF state to the ON state.

[0056] When the current control mode's level control state and the target control state's level control state include a high-level control state and / or an N-level control state, the intermediate control state is determined to be an OFF intermediate state and an N intermediate state; and when the current control mode's level control state and the target control state's level control state include a low-level control state and / or a P-level control state, the intermediate control state is determined to be an OFF intermediate state and a P intermediate state. By inserting two levels of intermediate control states, and switching only the on or off state of a single transistor each time, the simultaneous conduction of the first transistor T1 and the fourth transistor T4 can be effectively avoided, thereby avoiding the short-circuit risk of the T-type three-level circuit and improving the smoothness of the level control state switching.

[0057] S350. When the transistor that is not turned on in both the current control mode level control state and the target control state level control state is the first transistor, the intermediate control state is determined to be the N intermediate state.

[0058] Specifically, when the first transistor T1 is not conducting in both the current control mode level control state and the target control state level control state, the second transistor T2 and the fourth transistor T4 are conducting in both the current control mode level control state and the target control state level control state, respectively. In order to avoid the second transistor T2 and the fourth transistor T4 conducting at the same time, the intermediate control state is determined to be the N intermediate state. By setting the N intermediate state where the third transistor T3 is conducting and the first transistor T1, the second transistor T2 and the fourth transistor T4 are all off, the short circuit risk of the T-type three-level circuit can be effectively avoided.

[0059] In an optional embodiment, when the transistor that is not turned on in both the current control mode's level control state and the target control state's level control state is the first transistor, determining the intermediate control state as an N intermediate state includes: when the current control mode's level control state and the target control state's level control state include a low level control state and / or a 0 level control state, determining the intermediate control state as an N level control state and an N intermediate state; and controlling the conduction state of each transistor in the T-type three-level circuit according to the intermediate control state, including: when the current control mode's level control state is a low level control state and the target control state's level control state is a 0 level control state, controlling the conduction state of each transistor in the T-type three-level circuit according to the N level control state and the N intermediate state sequentially; otherwise, controlling the conduction state of each transistor in the T-type three-level circuit according to the N intermediate state and the N level control state sequentially.

[0060] Specifically, when the current control mode's level control state is low and the target control state's level control state is 0, the intermediate control state is first determined to be N, causing the third transistor T3 to switch from the off state to the on state. Then, the intermediate control state is determined to be N intermediate state, causing the fourth transistor T4 to switch from the on state to the off state. Finally, the control state is changed to 0, causing the second transistor T2 to switch from the off state to the on state. Conversely, when the current control mode's level control state is 0 and the target control state's level control state is low, the intermediate control state is first determined to be N intermediate state, causing the second transistor T2 to switch from the on state to the off state. Then, the intermediate control state is determined to be N level, causing the fourth transistor T4 to switch from the off state to the on state. Finally, the control state is changed to low, causing the third transistor T3 to switch from the on state to the off state.

[0061] When the level control state of the current control mode and the level control state of the target control state include low level control state and / or 0 level control state, the intermediate control state is determined to be N level control state and N intermediate state. By inserting two levels of intermediate control states, the conduction or cutoff state of only a single transistor is switched each time, which can effectively avoid the simultaneous conduction of the second transistor T2 and the fourth transistor T4, thereby avoiding the short circuit risk of the T-type three-level circuit and improving the smoothness of level control state switching.

[0062] S360. When the fourth transistor is not turned on in both the current control mode's level control state and the target control state's level control state, the intermediate control state is determined to be the P intermediate state.

[0063] Specifically, when the fourth transistor T4 is not conducting in both the current control mode level control state and the target control state level control state, the first transistor T1 and the third transistor T3 are conducting in both the current control mode level control state and the target control state level control state, respectively. In order to avoid the first transistor T1 and the third transistor T3 conducting at the same time, the intermediate control state is determined to be the P intermediate state. By setting the second transistor T2 to conduct and the first transistor T1, the third transistor T3 and the fourth transistor T4 to be off in the P intermediate state, the short circuit risk of the T-type three-level circuit can be effectively avoided.

[0064] In an optional embodiment, when the fourth transistor is not turned on in both the current control mode's level control state and the target control state's level control state, determining the intermediate control state as the P intermediate state includes: when the current control mode's level control state and the target control state's level control state include a high-level control state and / or a zero-level control state, determining the intermediate control state as a P-level control state and a P intermediate state; and controlling the conduction state of each transistor in the T-type three-level circuit according to the intermediate control state, including: when the current control mode's level control state is a high-level control state and the target control state's level control state is a zero-level control state, controlling the conduction state of each transistor in the T-type three-level circuit sequentially according to the P-level control state and the P intermediate state; otherwise, controlling the conduction state of each transistor in the T-type three-level circuit sequentially according to the P intermediate state and the P-level control state.

[0065] Specifically, when the current control mode's level control state is high and the target control state's level control state is 0, the intermediate control state is first determined to be P, causing the second transistor T2 to switch from the off state to the on state. Then, the intermediate control state is determined to be P intermediate state, causing the first transistor T1 to switch from the on state to the off state. Finally, the control state is changed to 0, causing the third transistor T3 to switch from the off state to the on state. Conversely, when the current control mode's level control state is 0 and the target control state's level control state is high, the intermediate control state is first determined to be P intermediate state, causing the third transistor T3 to switch from the on state to the off state. Then, the intermediate control state is determined to be P, causing the first transistor T1 to switch from the off state to the on state. Finally, the control state is changed to high, causing the second transistor T2 to switch from the on state to the off state.

[0066] When the current control mode's level control state and the target control state's level control state include a high-level control state and / or a zero-level control state, the intermediate control state is determined to be a P-level control state and a P intermediate state. By inserting two levels of intermediate control states, the on or off state of a single transistor is switched only at a time, which can effectively avoid the simultaneous conduction of the first transistor T1 and the third transistor T3, thereby avoiding the short-circuit risk of the T-type three-level circuit and improving the smoothness of the level control state switching.

[0067] S370. Based on the intermediate control state, control the conduction state of each transistor in the T-type three-level circuit.

[0068] S380. According to the level control state of the target control mode, control the conduction state of each transistor in the T-type three-level circuit so that the T-type three-level circuit drives the motor to achieve the target parameters.

[0069] In this embodiment, when the transistor that is not turned on in both the current control mode level control state and the target control state level control state is the second or third transistor, the intermediate control state is determined to be the OFF intermediate state; when the transistor that is not turned on in both the current control mode level control state and the target control state level control state is the first transistor, the intermediate control state is determined to be the N intermediate state; and when the transistor that is not turned on in both the current control mode level control state and the target control state level control state level control state is the fourth transistor, the intermediate control state is determined to be the P intermediate state. By inserting two levels of intermediate control states, and switching only the on or off state of a single transistor each time, the short-circuit risk of the T-type three-level circuit can be effectively avoided, and the smoothness of the level control state switching can be improved.

[0070] Example 4 Figure 5 This is a schematic diagram of the structure of a control device for an electric drive system of an electric vehicle provided in an embodiment of the present invention. This device can be used to control the electric drive system of an electric vehicle, which includes a motor and a T-type three-level circuit. The device can be implemented in software and / or hardware, and is generally integrated into the control system of the electric drive system provided in this embodiment of the present invention. Figure 5 As shown, the control device includes: The mode determination module 410 is used to determine the target control mode of the T-type three-level circuit based on the target parameters of the motor; wherein, the target control mode includes a two-level control mode and a three-level control mode; The state determination module 420 is used to determine the level control state of the target control mode based on the target parameters and the target control mode; wherein, when the target control mode is a two-level control mode, the level control state of the target control mode includes a high-level control state and a low-level control state; when the target control mode is a three-level control mode, the level control state of the target control mode includes a P-level control state, an O-level control state, and an N-level control state. The state control module 430 is used to control the conduction state of each transistor in the T-type three-level circuit according to the level control state of the target control mode, so that the T-type three-level circuit drives the motor to achieve the target parameters.

[0071] Optionally, the mode determination module 410 may include a mode determination unit; the mode determination unit is used to determine the target control mode of the T-type three-level circuit based on the target torque and / or target speed of the motor, and in the target control mode, the parameters of the electric drive system meet preset conditions.

[0072] Optionally, the control device further includes a mode acquisition module, an intermediate state determination module, and a transistor control module; the mode acquisition module is used to acquire the current control mode of the T-type three-level circuit; the intermediate state determination module is used to determine the intermediate control state when the current control mode is different from the target control mode; the transistor control module is used to control the conduction state of each transistor in the T-type three-level circuit according to the intermediate control state.

[0073] Optionally, the intermediate state determination module includes an OFF intermediate state determination unit, an N intermediate state determination unit, and a P intermediate state determination unit. The OFF intermediate state determination unit determines the intermediate control state as OFF when the transistor that is not turned on in both the current control mode's level control state and the target control state's level control state is the second or third transistor. The N intermediate state determination unit determines the intermediate control state as N when the transistor that is not turned on in both the current control mode's level control state and the target control state's level control state is the first transistor. The P intermediate state determination unit determines the intermediate control state as P when the transistor that is not turned on in both the current control mode's level control state and the target control state's level control state is the fourth transistor.

[0074] Optionally, the OFF intermediate state determination unit is specifically used to: determine the intermediate control state as OFF intermediate state and N intermediate state when the level control state of the current control mode and the level control state of the target control state include a high level control state and / or an N level control state; and determine the intermediate control state as OFF intermediate state and P intermediate state when the level control state of the current control mode and the level control state of the target control state include a low level control state and / or a P level control state.

[0075] Optionally, the transistor control module is specifically used to: control the conduction state of each transistor in the T-type three-level circuit according to the OFF intermediate state and the N intermediate state when the current control mode is in a high-level control state and the target control state is in an N-level control state; otherwise, control the conduction state of each transistor in the T-type three-level circuit according to the N intermediate state and the OFF intermediate state; when the current control mode is in a low-level control state and the target control state is in a P-level control state, control the conduction state of each transistor in the T-type three-level circuit according to the OFF intermediate state and the P intermediate state; otherwise, control the conduction state of each transistor in the T-type three-level circuit according to the P intermediate state and the OFF intermediate state.

[0076] Optionally, the N intermediate state is specifically used to: determine the intermediate control state as the N level control state and the N intermediate state when the level control state of the current control mode and the level control state of the target control state include a low level control state and / or a 0 level control state; the transistor control module is specifically used to: control the conduction state of each transistor in the T-type three-level circuit according to the N level control state and the N intermediate state sequentially when the level control state of the current control mode is a low level control state and the level control state of the target control state is a 0 level control state; otherwise, it controls the conduction state of each transistor in the T-type three-level circuit according to the N intermediate state and the N level control state sequentially.

[0077] Optionally, the P intermediate state is specifically used to: determine the intermediate control state as the P level control state and the P intermediate state when the level control state of the current control mode and the level control state of the target control state include a high level control state and / or a zero level control state; the transistor control module is specifically used to: control the conduction state of each transistor in the T-type three-level circuit according to the P level control state and the P intermediate state sequentially when the level control state of the current control mode is a high level control state and the level control state of the target control state is a zero level control state; otherwise, it controls the conduction state of each transistor in the T-type three-level circuit according to the P intermediate state and the P level control state sequentially.

[0078] It is understood that, since the control device for the electric drive system described above is capable of executing the control method for the electric drive system in any embodiment of the present invention, those skilled in the art can understand the specific implementation and various variations of the control device for the electric drive system in this embodiment based on the control method for the electric drive system described in the embodiments of the present invention. Therefore, how the control device for the electric drive system implements the control method for the electric drive system in the embodiments of the present invention will not be described in detail here. Any device used by those skilled in the art to implement the control method for the electric drive system in the embodiments of the present invention falls within the scope of protection of this application.

[0079] Example 5 The present invention also provides a control system for an electric drive system of an electric vehicle. The control system for the electric drive system of an electric vehicle includes a control device for the electric drive system, which is used to execute the control method of the electric drive system according to any embodiment of the present invention.

[0080] The control system of the electric drive system provided in this embodiment can execute the control method of the electric drive system of any embodiment of the present invention, and has the functional module for executing the control method of the electric drive system of any embodiment of the present invention. It can achieve the effect of the control method of the electric drive system of the above embodiment. The similarities can be referred to the above description, and will not be repeated here.

[0081] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A control method for an electric drive system of an electric vehicle, characterized in that, The electric drive system includes a motor and a T-type three-level circuit; the control method includes: Based on the target parameters of the motor, the target control mode of the T-type three-level circuit is determined; wherein, the target control mode includes a two-level control mode and a three-level control mode; Based on the target parameters and the target control mode, the level control state of the target control mode is determined; wherein, when the target control mode is the two-level control mode, the level control state of the target control mode includes a high-level control state and a low-level control state; when the target control mode is the three-level control mode, the level control state of the target control mode includes a P-level control state, an O-level control state, and an N-level control state. According to the level control state of the target control mode, the conduction state of each transistor in the T-type three-level circuit is controlled so that the T-type three-level circuit drives the motor to achieve the target parameters.

2. The control method for the electric drive system of an electric vehicle according to claim 1, characterized in that, The target parameters include target torque and / or target speed; Based on the target parameters of the motor, the target control mode of the T-type three-level circuit is determined, including: Based on the target torque and / or target speed of the motor, the target control mode of the T-type three-level circuit is determined, and under the target control mode, the parameters of the electric drive system meet preset conditions.

3. The control method for the electric drive system of an electric vehicle according to claim 1, characterized in that, Before controlling the conduction state of each transistor in the T-type three-level circuit according to the level control state of the target control mode, the method further includes: Obtain the current control mode of the T-type three-level circuit; When the current control mode differs from the target control mode, an intermediate control state is determined; Based on the intermediate control state, the conduction state of each transistor in the T-type three-level circuit is controlled; The T-type three-level circuit includes a first transistor, a second transistor, a third transistor, and a fourth transistor. The first transistor and the fourth transistor are connected in series between the positive terminal and the negative terminal of the DC bus, and the second transistor and the third transistor are connected in series between the midpoint of the DC bus and the output terminal. The intermediate control states include a P intermediate state where the second transistor is turned on, an N intermediate state where the third transistor is turned on, and an OFF intermediate state where all transistors are turned off.

4. The control method for the electric drive system of an electric vehicle according to claim 3, characterized in that, When the current control mode differs from the target control mode, an intermediate control state is determined, including: When either the second transistor or the third transistor is not turned on in both the level control state of the current control mode and the level control state of the target control state, the intermediate control state is determined to be the OFF intermediate state. When the first transistor is not turned on in both the level control state of the current control mode and the level control state of the target control state, the intermediate control state is determined to be the N intermediate state. When the fourth transistor is not turned on in both the current control mode's level control state and the target control state's level control state, the intermediate control state is determined to be the P intermediate state.

5. The control method for the electric drive system of an electric vehicle according to claim 4, characterized in that, When either the second transistor or the third transistor is not turned on in both the current control mode's level control state and the target control state's level control state, the intermediate control state is determined to be the OFF intermediate state, including: When the level control state of the current control mode and the level control state of the target control state include the high level control state and / or the N level control state, the intermediate control state is determined to be the OFF intermediate state and the N intermediate state. When the level control state of the current control mode and the level control state of the target control state include the low level control state and / or the P level control state, the intermediate control state is determined to be the OFF intermediate state and the P intermediate state.

6. The control method for the electric drive system of an electric vehicle according to claim 5, characterized in that, Based on the intermediate control state, the conduction state of each transistor in the T-type three-level circuit is controlled, including: When the current control mode's level control state is the high-level control state and the target control state's level control state is the N-level control state, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the OFF intermediate state and the N intermediate state; conversely, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the N intermediate state and the OFF intermediate state. When the current control mode's level control state is the low level control state and the target control state's level control state is the P level control state, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the OFF intermediate state and the P intermediate state; conversely, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the P intermediate state and the OFF intermediate state.

7. The control method for the electric drive system of an electric vehicle according to claim 4, characterized in that, When the first transistor is not turned on in both the current control mode's level control state and the target control state's level control state, the intermediate control state is determined to be the N intermediate states, including: When the level control state of the current control mode and the level control state of the target control state include the low level control state and / or the 0 level control state, the intermediate control state is determined to be the N level control state and the N intermediate state; Based on the intermediate control state, the conduction state of each transistor in the T-type three-level circuit is controlled, including: When the current control mode's level control state is the low level control state and the target control state's level control state is the 0 level control state, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the N level control state and the N intermediate state; conversely, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the N intermediate state and the N level control state.

8. The control method for the electric drive system of an electric vehicle according to claim 4, characterized in that, When the fourth transistor is the only transistor that is not turned on in both the current control mode's level control state and the target control state's level control state, the intermediate control state is determined to be the P intermediate state, including: When the level control state of the current control mode and the level control state of the target control state include the high level control state and / or the 0 level control state, the intermediate control state is determined to be the P level control state and the P intermediate state; Based on the intermediate control state, the conduction state of each transistor in the T-type three-level circuit is controlled, including: When the current control mode's level control state is the high-level control state and the target control state's level control state is the 0-level control state, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the P-level control state and the P intermediate state; conversely, the conduction state of each transistor in the T-type three-level circuit is controlled sequentially according to the P intermediate state and the P-level control state.

9. A control device for an electric drive system of an electric vehicle, characterized in that, The electric drive system includes a motor and a T-type three-level circuit; the control device includes: The mode determination module is used to determine the target control mode of the T-type three-level circuit based on the target parameters of the motor; wherein, the target control mode includes a two-level control mode and a three-level control mode; The state determination module is used to determine the level control state of the target control mode based on the target parameters and the target control mode; wherein, when the target control mode is the two-level control mode, the level control state of the target control mode includes a high-level control state and a low-level control state; when the target control mode is the three-level control mode, the level control state of the target control mode includes a P-level control state, an O-level control state, and an N-level control state. The state control module is used to control the conduction state of each transistor in the T-type three-level circuit according to the level control state of the target control mode, so that the T-type three-level circuit drives the motor to achieve the target parameters.

10. A control system for an electric drive system of an electric vehicle, characterized in that, The control system of the electric drive system of the electric vehicle includes the control device of the electric drive system as described in claim 9, for executing the control method of the electric drive system as described in any one of claims 1-8.

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