Circuit and method for diagnosing health state of battery system of electric vehicle

Abstract

The invention provides a diagnosis circuit and method for the health state of a battery system of an electric vehicle. The diagnosis circuit comprises a battery pack, a motor controller and a driving motor, the first end of the battery pack is connected with the center line of the driving motor through the pre-charging unit, the diagnosis circuit relay and the fuse, the first end of the battery pack is connected with the first end of the motor controller through the main positive relay, and the second end of the battery pack is connected with the second end of the motor controller through the negative relay and the sensor module. Three-phase stator windings of the driving motor are respectively connected with each inverter bridge power group in the motor controller module; and the control module, the bleeder resistor, the thin-film capacitor and all the inverter bridge power groups are connected to form a diagnosis circuit which is used for controlling the on-off of each inverter bridge power group and injecting alternating current voltage into the battery system. According to the invention, online measurement of the health state of the battery pack can be realized without adding extra hardware equipment, and the diagnosis cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of battery detection, and in particular to a diagnosis circuit and method for the health status of an electric vehicle battery system. Background Art

[0002] As the main energy storage unit of electric vehicles, the state of health (SoH) of lithium-ion batteries is directly related to the performance, safety and service life of electric vehicles.

[0003] Accurate diagnosis and prediction of the health status of battery systems are crucial to ensure the reliable operation of electric vehicles. At present, the commonly used diagnostic methods for the health status of electric vehicle battery systems include capacity decay analysis, internal resistance testing, and electrochemical impedance spectroscopy (EIS) measurement. EIS is a very effective method that can provide detailed information about the internal electrochemical process of the battery and conduct in-depth analysis of the battery's decay mechanism. This method is also the most commonly used diagnostic method.

[0004] However, traditional EIS measurements usually require expensive dedicated equipment and the battery needs to be removed from the vehicle, which not only increases costs but also affects the normal use of the vehicle. Summary of the invention

[0005] The embodiment of the present invention provides a circuit and method for diagnosing the health status of a battery system of an electric vehicle, so as to solve the problem that the current diagnostic method is high in cost and affects the normal use of the vehicle.

[0006] In a first aspect, an embodiment of the present invention provides a diagnostic circuit for the health status of an electric vehicle battery system, including a battery pack, a motor controller, and a drive motor;

[0007] The first end of the battery pack is connected to the center line of the drive motor through the pre-charging unit, the diagnostic circuit relay and the fuse, and the first end of the battery pack is connected to the first end of the motor controller through the main positive relay, the second end of the battery pack is connected to the second end of the motor controller through the negative relay and the sensor module, and the three-phase stator windings of the drive motor are respectively connected to each group of inverter bridge power groups in the motor controller module;

[0008] The motor controller includes multiple inverter bridge power groups, control modules, bleeder resistors and film capacitors. The control modules, bleeder resistors, film capacitors and all inverter bridge power groups are connected to form a diagnostic circuit, which is used to control the on and off of each inverter bridge power group and inject AC voltage into the battery system. When the diagnostic circuit enters the diagnostic mode, the inverter bridge power group corresponding to the target stator winding forms a resonant circuit with the bleeder resistor and film capacitor. The target stator winding is any one of the three-phase stator windings of the drive motor.

[0009] In a possible implementation, a diagnostic circuit for the health status of an electric vehicle battery system, each inverter bridge power group includes at least a first power switch tube and a second power switch tube, the base of the first power switch tube and the base of the second power switch tube are both electrically connected to a control module, the collector of the first power switch tube is connected to a first end of a motor controller, the emitter of the second power switch tube is connected to a second end of the motor controller, the emitter of the first power switch tube is connected to the collector of the second power switch tube, and the target stator winding of the drive motor is connected to the emitter of the first power switch tube and the collector of the second power switch tube; the target stator winding is any one of the three groups of stator windings.

[0010] In a possible implementation, in a diagnostic circuit for the health status of an electric vehicle battery system, a pre-charging unit includes a pre-charging resistor and a pre-charging relay switch.

[0011] In a possible implementation, in a diagnostic circuit for the health status of an electric vehicle battery system, a discharge resistor and a film capacitor are connected in parallel, a first end of the discharge resistor is connected to a first end of a motor controller, and a second end of the discharge resistor is connected to a second end of the motor controller.

[0012] In a possible implementation, a diagnostic circuit for the health status of an electric vehicle battery system, a battery pack includes a plurality of battery module units, and a sensor module is used to detect the current and voltage of the battery pack.

[0013] In a possible implementation, in a diagnostic circuit for the health status of an electric vehicle battery system, each battery module unit is provided with a detection unit matched with the battery module unit, and the detection unit is used to detect the voltage and / or current of the battery module unit.

[0014] In a second aspect, an embodiment of the present invention provides a method for diagnosing the health status of an electric vehicle battery system. Based on the diagnostic circuit for the health status of an electric vehicle battery system according to any one of the first aspects, the diagnostic method includes:

[0015] When the low-voltage system of the electric vehicle is powered on and enters the battery fault diagnosis and evaluation mode and the battery system is detected to be normal, it enters the diagnosis mode, controls the diagnosis circuit relay to close and controls the main positive relay to disconnect;

[0016] Control the inverter bridge power group corresponding to the target stator winding to turn on and off at a preset frequency, disturb the battery pack, and detect the current and voltage of the battery pack under disturbance; wherein the target stator winding is any phase of the three-phase stator winding of the drive motor;

[0017] Determine the detection impedance value of the battery pack at a preset frequency at a target time based on the detected current and voltage;

[0018] The health status of the battery pack is determined based on the detected impedance value, the temperature at the target time, the battery pack SOC value at the target time and the preset impedance comparison table.

[0019] In a possible implementation, determining the health state of the battery pack based on the detected impedance value, the temperature at the target time, the SOC value of the battery pack at the target time, and a preset impedance comparison table includes:

[0020] Based on the detection impedance value, the temperature at the target time, and the SOC value of the battery pack at the target time, a comparison impedance corresponding to the detection impedance value is determined in a preset impedance comparison table; wherein the preset impedance comparison table is an impedance table corresponding to a preset frequency;

[0021] Based on the detection impedance value and the control impedance, the health state of the battery pack is determined.

[0022] In a possible implementation, determining the detection impedance value of the battery pack at a preset frequency at a target time based on the detected current and voltage includes:

[0023] When it is detected that the difference between the voltage peak value and the voltage valley value is greater than or equal to the preset difference value, the power is turned on again to continue monitoring;

[0024] When it is detected that the difference between the voltage peak value and the voltage valley value is less than the preset difference value, the output voltage peak value and the output current peak value are determined based on the average of the voltage peak value and the current peak value detected multiple times;

[0025] Based on the output voltage peak and the output current peak, determine the detection impedance value of the battery pack at the preset frequency at the target time.

[0026] In a possible implementation, after controlling the inverter bridge power group corresponding to the target stator winding to be turned on and off at a preset frequency to disturb the battery pack, and detecting the current and voltage of the battery pack under the disturbance, it also includes:

[0027] Detecting the voltage and current of a target battery module under disturbance; wherein the target battery module is any battery module;

[0028] Determine the detection impedance value of the target battery module at the preset frequency at the target time based on the detected current and voltage;

[0029] Based on the detected impedance values ​​of all target battery modules and a preset total impedance threshold, it is determined whether there is a fault in the connection lines between the target battery modules.

[0030] The embodiment of the present invention provides a diagnostic circuit for the health status of an electric vehicle battery system. When entering the diagnostic mode, the motor controller disturbs the stator winding of the drive motor in the electric vehicle by inductive means, thereby forming a resonant circuit, and the motor controller controls the on and off of each inverter bridge power group, thereby determining the health status of the battery system, thereby realizing online measurement of battery EIS without adding additional detection equipment. In addition, the impedance of the battery pack is obtained through the inductive disturbance of the stator winding by the motor controller, thereby realizing online diagnosis of the health status of the battery pack, avoiding the problem of having to disassemble the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 is a schematic diagram of a diagnostic circuit for the health status of an electric vehicle battery system provided by an embodiment of the present invention;

[0033] Figure 2 It is a process flowchart of a method for diagnosing the health status of an electric vehicle battery system provided by an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of a diagnostic circuit provided by an embodiment of the present invention when the W phase is used as the inductor element under detection;

[0035] Figure 4 It is a flow chart of a method for diagnosing the health status of an electric vehicle battery system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0038] As introduced in the background art, currently commonly used EIS measurements usually require expensive dedicated equipment and the battery needs to be removed from the vehicle for testing, which not only increases the testing cost but also affects the normal use of the vehicle.

[0039] How to measure the battery in real time and conveniently without affecting the normal operation of electric vehicles has become a hot topic in current research.

[0040] In order to solve the problems in the prior art, an embodiment of the present invention provides a circuit and method for diagnosing the health status of an electric vehicle battery system. First, the circuit for diagnosing the health status of an electric vehicle battery system provided by an embodiment of the present invention is introduced below.

[0041] See also Figure 1 , which shows a schematic diagram of a diagnostic circuit for the health status of an electric vehicle battery system provided by an embodiment of the present invention, and is described in detail as follows:

[0042] A diagnostic circuit for the health status of an electric vehicle battery system, wherein the battery system includes a battery pack 110 , a motor controller 120 and a drive motor 130 .

[0043] Specifically, the first end of the battery pack 110 is connected to the center line of the drive motor 130 through the pre-charging unit, the diagnostic circuit relay S2 and the fuse F2, and the first end of the battery pack 110 is connected to the first end of the motor controller 120 through the main positive relay S3, and the second end of the battery pack 110 is connected to the second end of the motor controller 120 through the negative relay S4 and the sensor module 1110, and the three-phase stator windings of the drive motor 130 are respectively connected to the inverter bridge power group in the motor controller module. The first end of the motor controller 120 is connected to the positive electrode of the battery pack 110, and the second end of the motor controller 120 is connected to the negative electrode of the battery pack 110.

[0044] The motor controller 120 includes multiple inverter bridge power groups, a control module 1210, a bleeder resistor, and a film capacitor. The control module 1210, the bleeder resistor, and the film capacitor are connected to all the inverter bridge power groups to form a diagnostic circuit for controlling the on and off of each inverter bridge power group and injecting AC voltage into the battery system. When the diagnostic circuit enters the diagnostic mode, the inverter bridge power group corresponding to the target stator winding forms a resonant circuit with the bleeder resistor and the film capacitor. The target stator winding is any one of the three-phase stator windings of the drive motor.

[0045] In this embodiment, the battery pack 110 includes a plurality of battery module units. Figure 1M0 and Mx are battery module units, and a fuse F0 is also connected between the battery module units. The sensor module 1110 is used to detect the current and voltage of the battery pack 110. The impedance value of the battery pack can be calculated by the voltage and current of the battery pack 110 detected by the sensor module 1110. Therefore, the health status of the battery pack can be determined based on the determined impedance value of the battery pack and the reference impedance in the preset impedance comparison table. Among them, the sensor module 1110 is a high-precision sensor.

[0046] Each battery module unit is provided with a detection unit matched with the battery module unit, and the detection unit is used to detect the voltage of the battery module unit. Each battery module unit adopts a series mode so that the current is the same. The impedance value of each battery module can be determined by the voltage and current of each battery module. The impedance value of each battery module and the set total impedance value can also be used to detect the performance of the connection between the circuit and the electronic device in the battery pack, and determine the connection reliability and stability of the battery pack system.

[0047] In some embodiments, in order to disturb the detection circuit and inject AC voltage into the battery system, it can be achieved by controlling the on and off of the inverter bridge power group.

[0048] In this embodiment, each inverter bridge power group includes at least a first power switch tube and a second power switch tube, the base of the first power switch tube and the base of the second power switch tube are both electrically connected to the control module 1210, the collector of the first power switch tube is connected to the first end of the motor controller 120, the emitter of the second power switch tube is connected to the second end of the motor controller 120, the emitter of the first power switch tube is connected to the collector of the second power switch tube, and the target stator winding of the drive motor 130 is connected to the emitter of the first power switch tube and the collector of the second power switch tube. Wherein, the target stator winding is any group of the three-phase stator windings.

[0049] Specifically, it may include three inverter bridge power groups, such as Figure 1 As shown, Q1 and Q4 form a group of inverter bridge power groups, Q2 and Q5 form a group of inverter bridge power groups, and Q3 and Q6 form a group of inverter bridge power groups. The V-phase stator winding of the drive motor 130 is connected to the emitter of Q1 and the collector of Q4, the U-phase stator winding of the drive motor 130 is connected to the emitter of Q2 and the collector of Q5, and the W-phase stator winding of the drive motor 130 is connected to the emitter of Q3 and the collector of Q6. By controlling the opening and closing of different groups of inverter bridge power groups to make the circuit resonant, the voltage disturbance of the entire detection circuit can be achieved, and the AC voltage can be injected into the battery pack.

[0050] In some embodiments, Figure 1As shown, the pre-charging unit includes a pre-charging resistor R1 and a pre-charging relay switch S1 connected in series with the resistor.

[0051] In this embodiment, the motor controller 120 further includes a bleeder resistor R2 and a film capacitor C1. When entering the diagnostic mode, the switch S5 is closed, and the bleeder resistor R2 and the film capacitor C1 are connected in parallel. The first end of the bleeder resistor R2 is connected to the first end of the motor controller 120, and the second end of the bleeder resistor R2 is connected to the second end of the motor controller 120.

[0052] The electric vehicle battery system health status diagnosis circuit provided by the present invention can determine the health status of the battery system based on the inductive disturbance of the stator winding of the drive motor in the electric vehicle by the motor controller, thereby realizing the online measurement of the battery EIS without adding additional detection equipment. In addition, the impedance of the battery pack is obtained through the inductive disturbance of the stator winding by the motor controller, thereby realizing the online diagnosis of the health status of the battery pack and avoiding the problem of having to disassemble the battery pack.

[0053] Based on the electric vehicle battery system health status diagnosis circuit provided in the above embodiment, the present invention also provides a specific implementation of the electric vehicle battery system health status diagnosis method applied to the electric vehicle battery system health status diagnosis circuit. Please refer to the following embodiment.

[0054] like Figure 2 As shown, a schematic diagram of a method for diagnosing the health status of an electric vehicle battery system provided by an embodiment of the present invention is described in detail as follows:

[0055] S210: When the low-voltage system of the electric vehicle is powered on and enters the battery fault diagnosis and evaluation mode and the battery system is detected to be normal, it enters the diagnosis mode, controls the diagnosis circuit relay to close, and controls the main positive relay to disconnect.

[0056] After the low-voltage system of the electric vehicle is powered on and enters the battery fault diagnosis and evaluation mode, the control unit needs to first perform a short-circuit detection on the electric vehicle. Only after determining that the short-circuit detection is normal, that is, the system detection is normal, can the diagnostic circuit relay be controlled to close. After the diagnostic circuit relay S2 is closed and the main positive relay S3 is disconnected, in order to realize the charge and discharge test of the entire battery pack, the control module will control all power tubes Q1-Q6 at the same time.

[0057] S220, controlling the inverter bridge power group corresponding to the target stator winding to be turned on and off at a preset frequency, disturbing the battery pack, and detecting the current and voltage of the battery pack under disturbance.

[0058] The drive motor has a three-phase stator winding. When the disturbance is performed, it is only necessary to control the inverter bridge power group corresponding to one phase of the stator winding to turn on and off each time. When the W phase is used as the inductor element in the detection, the corresponding current flow circuit is as follows Figure 3 shown.

[0059] During steady-state operation the output voltage of the battery pack is set to V DC At this time, the discharge resistor R2 can be regarded as a load, and the voltage across it is consistent with the output voltage of the battery pack. When the control module 1210 controls the inverter bridge power groups Q1 and Q6 to turn on and off continuously, the original output voltage V DC A disturbance signal V with a small duty cycle is added ac , the corresponding frequency is f p At this time, the corresponding battery pack voltage V dc-batt With current I dc-batt It can be expressed by the following formula:

[0060]

[0061] At this time, the voltage peak and current peak added to the circuit after the disturbance is detected are V batt-peak and I batt-peak Corresponding to the frequency f p The impedance value is:

[0062]

[0063] If there is a phase change between the battery pack voltage and the battery pack current, or if phase information is required, f can be determined by the following formula: p The phase of .

[0064]

[0065] At this time, the control module is used to p The frequency controls the on and off of Q3 and Q6 to perform charge and discharge disturbance tests on the entire battery pack. The sensor module in the system detects the current and voltage of the entire battery pack.

[0066] S230: Determine the detection impedance value of the battery pack at a preset frequency at a target time based on the detected current and voltage.

[0067] In some embodiments, Figure 4As shown, due to external interference and other factors, the peak voltage or current detected before and after may be inconsistent, affecting the accuracy of battery impedance detection. Therefore, when the voltage peak and voltage valley are detected, a subtraction operation is performed, and the stability is determined by determining the difference between the two voltage peaks and voltage valleys and the preset difference. For example, the difference between the peak-valley value detected at n is X(n) and the difference between the peak-valley value detected at n-1 is X(n-1). If X(n)-X(n-1)<Th, then it proves that the system is in a stable state, and continues to detect and record the detected current peak and voltage peak. In order to improve the detection accuracy, M consecutive tests can be performed, and the average value of the M differences is taken as the final output current peak and voltage peak. Th is the preset difference.

[0068] However, if the difference between the peak-to-valley values ​​of the two preceding and succeeding times is greater than the preset difference, it is necessary to power on again and wait for a certain period of time before continuing monitoring.

[0069] At this time, after the voltage peak value and the current peak value superimposed on the circuit after the disturbance are detected, the detection impedance value can be determined based on the voltage peak value and the current peak value.

[0070] The peak voltage and current are V batt-peak and I batt-peak Corresponding to the frequency f p The detection impedance value is:

[0071]

[0072] If there is a phase change between the battery pack voltage and the battery pack current, or if phase information is required, f can be determined by the following formula: p The phase of .

[0073]

[0074] In addition, in order to improve the accuracy of the detection impedance value of the determined battery pack at the preset frequency at the target time, the inverter bridge power group corresponding to each phase of the stator winding can be turned on and off at a preset frequency, the battery pack can be disturbed, and the current and voltage of the battery pack under disturbance can be detected. Thereby, the detection impedance values ​​of three battery packs will be obtained, and the average of these three detection impedance values ​​will be used as the final detection impedance value of the battery pack. It should be noted that the inverter bridge power group corresponding to each phase of the stator winding is turned on and off at a preset frequency, which needs to be done at the same temperature and when the SOC value of the battery pack is the same.

[0075] In addition, in order to further detect the performance of the connection between the circuits and electronic devices in the battery pack, it is also possible to first detect the voltage and current of the target battery module under disturbance, and then determine the detection impedance value of the target battery module at the target time based on the detected current and voltage. Finally, based on the detection impedance values ​​of all target battery modules at the target time and the preset total impedance threshold, it is determined whether there is a fault in the connection line between the target battery modules.

[0076] S240 , determining a health status of the battery pack based on the detected impedance value, the temperature at the target time, the SOC value of the battery pack at the target time, and a preset impedance comparison table.

[0077] The temperature at the target time and the SOC value of the battery pack at the target time can be obtained through the battery management system.

[0078] In some embodiments, first, based on the detection impedance value, the temperature at the target time, and the battery pack SOC value at the target time, the control impedance corresponding to the detection impedance value can be determined in the preset impedance comparison table. It should be noted that the control impedance corresponding to the detection impedance value needs to be determined in the preset impedance comparison table at the preset frequency.

[0079] Then, based on the detected impedance value and the control impedance, the health state of the battery pack is determined.

[0080] In this embodiment, when the detection impedance value is less than the control impedance, it is determined that the battery pack is in a healthy state.

[0081] Specifically, when the detection impedance value is greater than or equal to a first preset multiple of the control impedance and less than a second preset multiple of the control impedance, the health state of the battery pack is determined to be level 1. Exemplarily, the first preset multiple may be 0, and the second preset multiple may be 10%.

[0082] When the detection impedance value is greater than or equal to the second preset multiple of the control impedance and less than the third preset multiple of the control impedance, the health state of the battery pack is determined to be level 2. For example, the second preset multiple may be 10% and the third preset multiple may be 30%.

[0083] When the detection impedance value is greater than or equal to a second preset multiple of the control impedance, it is determined that the health state of the battery pack is serious, indicating that the battery pack needs to be replaced.

[0084] For example, the preset impedance comparison table at the preset frequency may be shown in Table 1 below:

[0085] Table 1 Comparison table of preset impedance of battery pack

[0086]

[0087] The first column in Table 1 is the temperature, and the subsequent columns are the battery pack SOC values. Based on the temperature at the target time and the battery pack SOC value at the target time, the comparison impedance corresponding to the detection impedance value at the preset frequency at the target time can be determined in the preset impedance comparison table of the battery pack.

[0088] Similarly, Table 2 is a comparison table of preset impedances of battery modules at preset frequencies:

[0089] Table 2 Comparison table of preset impedance of battery module

[0090]

[0091] The method for diagnosing the health status of the battery system of an electric vehicle provided by the present invention uses a constructed diagnostic circuit for the health status of the battery system of an electric vehicle. When the low-voltage system of the electric vehicle is powered on and enters the battery fault diagnosis and evaluation mode and the battery system is detected normally, the diagnostic mode can be entered, the diagnostic circuit relay is controlled to close, and the main positive relay is controlled to disconnect. Then, the inverter bridge power group corresponding to the target stator winding is controlled to turn on and off at a preset frequency, the battery pack is disturbed, and the current and voltage of the battery pack under disturbance are detected. After the voltage and current of the battery pack are detected, the detection impedance value of the battery pack at the preset frequency at the target time can be determined based on the detected data. Finally, the health status of the battery pack is determined based on the detection impedance value, the temperature at the target time, the battery pack SOC value at the target time, and the preset impedance comparison table. The diagnostic method provided by the present invention can obtain the impedance value of the battery pack by controlling the inverter bridge power group corresponding to the target stator winding to turn on and off at a preset frequency to disturb the battery pack, thereby realizing online real-time diagnosis of the battery health status, avoiding the use of additional hardware equipment, and detecting without disassembling the battery pack, thereby realizing efficient and accurate diagnosis of the battery pack. The present invention makes full use of the existing drive motor and control module of the electric vehicle, making the diagnostic system more concise and lower in cost.

[0092] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

Claims

1. A diagnostic circuit for the health status of an electric vehicle battery system, characterized in that: The battery system includes a battery pack, a motor controller, and a drive motor; The first end of the battery pack is connected to the center line of the drive motor through a pre-charging unit, a diagnostic circuit relay and a fuse, and the first end of the battery pack is connected to the first end of the motor controller through a main positive relay, and the second end of the battery pack is connected to the second end of the motor controller through a negative relay and a sensor module, and the three-phase stator windings of the drive motor are respectively connected to each group of inverter bridge power groups in the motor controller module; The motor controller includes multiple inverter bridge power groups, a control module, a bleeder resistor and a thin film capacitor. The control module, the bleeder resistor, the thin film capacitor and all the inverter bridge power groups are connected to form a diagnostic circuit for controlling the on and off of each inverter bridge power group and injecting AC voltage into the battery system. When the diagnostic circuit enters the diagnostic mode, the inverter bridge power group corresponding to the target stator winding forms a resonant circuit with the bleeder resistor and the thin film capacitor. The target stator winding is any one of the three-phase stator windings of the drive motor.

2. The electric vehicle battery system health status diagnosis circuit as claimed in claim 1, characterized in that: Each inverter bridge power group includes at least a first power switch tube and a second power switch tube, the base of the first power switch tube and the base of the second power switch tube are both electrically connected to the control module, the collector of the first power switch tube is connected to the first end of the motor controller, the emitter of the second power switch tube is connected to the second end of the motor controller, the emitter of the first power switch tube is connected to the collector of the second power switch tube, and the target stator winding of the drive motor is connected to the emitter of the first power switch tube and the collector of the second power switch tube.

3. The electric vehicle battery system health status diagnosis circuit as claimed in claim 1 or 2, characterized in that: The pre-charging unit includes a pre-charging resistor and a pre-charging relay switch.

4. The electric vehicle battery system health status diagnosis circuit as claimed in claim 1, characterized in that: The discharge resistor and the film capacitor are connected in parallel, a first end of the discharge resistor is connected to a first end of the motor controller, and a second end of the discharge resistor is connected to a second end of the motor controller.

5. The electric vehicle battery system health status diagnosis circuit as claimed in claim 1, characterized in that: The battery pack includes a plurality of battery module units, and the sensor module is used to detect the current and voltage of the battery pack.

6. The electric vehicle battery system health status diagnosis circuit as claimed in claim 5, characterized in that: Each of the battery module units is provided with a detection unit matched with the battery module unit, and the detection unit is used to detect the voltage and / or current of the battery module unit.

7. A method for diagnosing the health status of an electric vehicle battery system, characterized in that: Based on the electric vehicle battery system health status diagnosis circuit according to any one of claims 1 to 6, the diagnosis method comprises: When the low-voltage system of the electric vehicle is powered on and enters the battery fault diagnosis and evaluation mode and the battery system is detected to be normal, it enters the diagnosis mode, controls the diagnosis circuit relay to close and controls the main positive relay to disconnect; Control the inverter bridge power group corresponding to the target stator winding to turn on and off at a preset frequency, disturb the battery pack, and detect the current and voltage of the battery pack under disturbance; wherein the target stator winding is any one phase of the three-phase stator winding of the drive motor; Determine, based on the detected current and voltage, a detection impedance value of the battery pack at a preset frequency at a target time; The health state of the battery pack is determined based on the detected impedance value, the temperature at the target time, the SOC value of the battery pack at the target time and a preset impedance comparison table.

8. The method for diagnosing the health status of an electric vehicle battery system as claimed in claim 7, characterized in that: The determining the health state of the battery pack based on the detected impedance value, the temperature at the target time, the SOC value of the battery pack at the target time and a preset impedance comparison table includes: Based on the detection impedance value, the temperature at the target time, and the battery pack SOC value at the target time, determining the comparison impedance corresponding to the detection impedance value in the preset impedance comparison table; wherein the preset impedance comparison table is an impedance table corresponding to the preset frequency; Based on the detection impedance value and the control impedance, a health state of the battery pack is determined.

9. The method for diagnosing the health status of an electric vehicle battery system as claimed in claim 7, characterized in that: The step of determining the detection impedance value of the battery pack at a preset frequency at a target time based on the detected current and voltage includes: When it is detected that the difference between the voltage peak value and the voltage valley value is greater than or equal to the preset difference value, the power is turned on again to continue monitoring; When it is detected that the difference between the voltage peak value and the voltage valley value is less than the preset difference value, the output voltage peak value and the output current peak value are determined based on the average of the voltage peak value and the current peak value detected multiple times; Based on the output voltage peak value and the output current peak value, a detection impedance value of the battery pack at a preset frequency at a target time is determined.

10. The method for diagnosing the health status of an electric vehicle battery system as claimed in claim 7, characterized in that: The inverter bridge power group corresponding to the control target stator winding is turned on and off at a preset frequency to disturb the battery pack, and the current and voltage of the battery pack under disturbance are detected, and further comprising: Detecting the voltage and current of a target battery module under disturbance; wherein the target battery module is any battery module; Determine the detection impedance value of the target battery module at a preset frequency at a target time based on the detected current and voltage; Based on the detected impedance values ​​of all the target battery modules and a preset total impedance threshold, it is determined whether there is a fault in the connection lines between the target battery modules.

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