A device, method and vehicle for detecting a safe state of an electric drive system

Abstract

The application provides a detection method and device for the safety state of an electric drive system and a vehicle. The detection device comprises a first resistor and a second resistor. The first resistor is connected in parallel between the two ends of each upper bridge arm of a switching element, and the second resistor is connected in parallel between the two ends of each lower bridge arm of the switching element. The detection device further comprises an upper bridge voltage detector and a lower bridge voltage detector. The upper bridge voltage detector is connected in parallel between the two ends of each first resistor, and the lower bridge voltage detector is connected in parallel between the two ends of each second resistor. The application adds a resistor voltage division circuit to the rear stage of the upper bridge arm and the lower bridge arm, and determines the safety state according to the different voltage values at the two ends of the resistor. The application can directly detect whether the drive circuit actually performs active short-circuit or safety pulse shutdown operation according to the actual instruction of the controller, is simple and easy to implement, and will not generate unintended torque. During the detection process, no current will enter the motor, so that the vehicle will not shake and is safe and reliable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric vehicles, in particular to a detection device and method for the safe state of an electric drive system and a vehicle. BACKGROUND

[0002] At present, with the increasing seriousness of global environmental problems, new energy vehicles such as electric vehicles have developed rapidly.

[0003] Among them, the motor controller in the electric vehicle not only controls the torque output of the motor when the electric vehicle is normally driven, but also ensures that the motor enters a safe state when a fault occurs, i.e. active short circuit (ASC) or safety pulse off (SPO), so as to ensure the safety of vehicle driving.

[0004] In the prior art, the working state of an Insulated Gate Bipolar Transistor (IGBT) single bridge arm is detected by opening one of the upper and lower bridge arms in an opposite phase, i.e. when the next U-phase upper bridge is opened and the V-phase lower bridge is given a small duty cycle, the next U-phase upper bridge is opened and the W-phase lower bridge is given a small duty cycle. In this way, the value of the three-phase current is determined by detecting the single bridge arm whether it can work normally by operating two bridge arms each time. However, the above-mentioned method will generate current and produce unexpected torque, causing the vehicle to vibrate. At the same time, the above-mentioned small duty cycle is difficult to control and needs to be calibrated by multiple attempts. Moreover, the above-mentioned method only operates two bridge arms each time, which needs to be detected multiple times and is relatively cumbersome. In addition, the above-mentioned method can detect whether each bridge arm can be normally opened and closed, but cannot guarantee that the three-phase active short circuit is definitely correct. SUMMARY

[0005] Therefore, the present application aims to provide a detection device and method for the safe state of an electric drive system and a vehicle to solve the problem that the prior art cannot effectively detect whether the electric drive system can normally enter a safe state when the drive circuit is controlled to enter an active short circuit state.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application is as follows:

[0007] A detection device for the safe state of an electric drive system, comprising a controller, a drive circuit and a switching element, wherein the controller is electrically connected to the drive circuit, and the switching element is electrically connected to the drive circuit,

[0008] The switching element includes three upper bridge arms and three lower bridge arms, each of the upper bridge arms is connected with one of the lower bridge arms, the upper bridge arms are electrically connected to the first electrode of the power supply of the electric drive system, the lower bridge arms are electrically connected to the second electrode of the power supply, and the three-phase input end of the motor of the electric drive system is electrically connected between the upper bridge arm and the corresponding lower bridge arm;

[0009] The detection device further includes first resistors and second resistors, one of the first resistors is connected in parallel between the two ends of each of the upper bridge arms, and one of the second resistors is connected in parallel between the two ends of each of the lower bridge arms.

[0010] The detection device further includes upper bridge voltage detectors and lower bridge voltage detectors, one of the upper bridge voltage detectors is connected in parallel between the two ends of each of the first resistors, and one of the lower bridge voltage detectors is connected in parallel between the two ends of each of the second resistors.

[0011] Further, in the detection device, the resistance value of the first resistor is the same as the resistance value of the second resistor.

[0012] Further, in the detection device, the detection device further includes first voltage dividing resistors and second voltage dividing resistors, each of the first resistors is connected in series with one of the first voltage dividing resistors and then connected in parallel between the two ends of the upper bridge arm, and each of the second resistors is connected in series with one of the second voltage dividing resistors and then connected in parallel between the two ends of the lower bridge arm, the resistance value of the first voltage dividing resistor is the same as the resistance value of the second voltage dividing resistor.

[0013] Further, in the detection device, the switching element is an insulated gate bipolar transistor, one of the first resistors is connected in parallel on each of the upper bridge arms of the insulated gate bipolar transistor, and each of the first resistors is connected in series with one of the first voltage dividing resistors; one of the second resistors is connected in parallel on each of the lower bridge arms of the insulated gate bipolar transistor, and each of the second resistors is connected in series with one of the second voltage dividing resistors.

[0014] Further, in the detection device, the controller is electrically connected with each of the upper bridge voltage detectors and each of the lower bridge voltage detectors.

[0015] Another purpose of the embodiment of the present application is to provide a detection method of safety state of an electric drive system, which is applied to a controller, the controller is electrically connected with a drive circuit, the drive circuit is electrically connected with switching elements, the switching elements include three upper bridge arms and three lower bridge arms, each upper bridge arm is connected with one lower bridge arm, the upper bridge arm is electrically connected with a first electrode of a power supply of the electric drive system, the lower bridge arm is electrically connected with a second electrode of the power supply, three-phase input terminals of a motor of the electric drive system are electrically connected between the upper bridge arm and the corresponding lower bridge arm, one first resistor is connected in parallel between the two ends of each upper bridge arm, and one second resistor is connected in parallel between the two ends of each lower bridge arm; one upper bridge voltage detector is connected in parallel between the two ends of each first resistor, and one lower bridge voltage detector is connected in parallel between the two ends of each second resistor.

[0016] The method comprises:

[0017] When the electric drive system is started, the drive circuit is controlled to output a pulse width modulation wave to control the upper bridge arms and / or the lower bridge arms to be turned off;

[0018] When the upper bridge arms are controlled to be turned off and the lower bridge arms are controlled to be turned on, the first voltage division on each first resistor is obtained through the upper bridge voltage detector, and the second voltage division on each second resistor is obtained through the lower bridge voltage detector;

[0019] When the lower bridge arms are controlled to be turned off and the upper bridge arms are controlled to be turned on, the third voltage division on each first resistor is obtained through the upper bridge voltage detector, and the fourth voltage division on each second resistor is obtained through the lower bridge voltage detector;

[0020] When the upper bridge arms and the lower bridge arms are controlled to be turned off, the fifth voltage division on each first resistor is obtained through the upper bridge voltage detector, and the sixth voltage division on each second resistor is obtained through the lower bridge voltage detector;

[0021] According to the first voltage division, the second voltage division, the third voltage division, the fourth voltage division, the fifth voltage division and the sixth voltage division, the safety state of the electric drive system is determined.

[0022] Further, in the detection method, the resistance of each first resistor is the same as the resistance of each second resistor, and the determination of the safety state of the electric drive system according to the first voltage division, the second voltage division, the third voltage division, the fourth voltage division, the fifth voltage division and the sixth voltage division comprises:

[0023] If each of the first voltage division and each of the third voltage division are less than a first threshold value, and each of the second voltage division and each of the fourth voltage division are greater than a second threshold value, and the average of each of the fifth voltage division and each of the sixth voltage division is greater than a third threshold value and less than a fourth threshold value, it is determined that the electric drive system is in a safe state.

[0024] Further, in the detection method, each of the first resistors and the corresponding first voltage division resistor are connected in series and then connected in parallel between the corresponding upper bridge arm, and each of the second resistors and the corresponding second voltage division resistor are connected in series and then connected in parallel between the corresponding lower bridge arm, the resistance value of the first voltage division resistor is the same as the resistance value of the second voltage division resistor.

[0025] The first threshold value is V1, the second threshold value is V2, the third threshold value is V3, and the fourth threshold value is V4; wherein V0=Vdc×R2 / (R1+R2); V1=k1×V0; V2=C; V3=k2×V0 / 2; V4=k1×V0 / 2; C is a constant greater than 0 and close to 0, k1 is a coefficient less than 1 and close to 1, k2 is a coefficient greater than 1 and close to 1, Vdc is the voltage of the power supply of the electric drive system, R1 is the resistance value of the first voltage division resistor, and R2 is the resistance value of the first resistor.

[0026] Further, the method further comprises:

[0027] If each of the first voltage division is not less than the first threshold value, or each of the third voltage division is not less than the first threshold value, or each of the second voltage division is not greater than the second threshold value, or each of the fourth voltage division is not greater than the second threshold value, or the average of each of the fifth voltage division and each of the sixth voltage division does not satisfy greater than the third threshold value and less than the fourth threshold value, the error number is incremented by 1;

[0028] Determine whether the error number reaches a preset number threshold value;

[0029] If the error number reaches the preset number threshold value, it is determined that the electric drive system is not in a safe state.

[0030] Further, the detection method further comprises:

[0031] If the error number does not reach the preset number threshold value, re-enter the step of controlling the drive circuit to output a pulse width modulation wave to control the upper bridge arm and / or the lower bridge arm to be turned off.

[0032] Further, in the detection method, after the first and third voltages are less than the first threshold, the second and fourth voltages are greater than the second threshold, and the average of the fifth and sixth voltages is greater than the third threshold and less than the fourth threshold, the electric drive system is determined to be in a safe state, and the method further comprises:

[0033] The error number is cleared.

[0034] Further, in the detection method, the preset number threshold is 3, 4 or 5.

[0035] Another purpose of the present application is to provide a vehicle, wherein the vehicle further comprises the detection device for the safe state of the electric drive system as described above.

[0036] Compared with the prior art, the detection device, method and vehicle for the safe state of the electric drive system have the following advantages:

[0037] The detection device comprises first resistors and second resistors, the first resistors are connected in parallel between both ends of each upper bridge arm of the switching element, and the second resistors are connected in parallel between both ends of each lower bridge arm of the switching element; the detection device further comprises an upper bridge voltage detector and a lower bridge voltage detector; the upper bridge voltage detector is connected in parallel between both ends of each first resistor, and the lower bridge voltage detector is connected in parallel between both ends of each second resistor. By adding a resistance voltage dividing circuit at the rear stage of the upper bridge arm and the lower bridge arm, the safe state is determined by the different voltage values between the two resistors, the driving circuit can be directly detected whether it is actually short-circuited or safety pulse off operated according to the actual instruction of the controller, which is simple and easy to implement, and will not produce unexpected torque. In the detection process, no current enters the motor, so as to avoid vehicle shaking and ensure safety and reliability. BRIEF DESCRIPTION OF DRAWINGS

[0038] The accompanying drawings, which form a part of the present application, are intended to provide further understanding of the present application, and the illustrative embodiments thereof and their descriptions serve to explain the present application. In the drawings:

[0039] Figure 1 The detection device for the safe state of the electric drive system according to the present application is shown in the structural schematic diagram;

[0040] Figure 2 The control structure of the electric drive system according to the present application is shown in the structural schematic diagram;

[0041] Figure 3 The detection method for the safe state of the electric drive system according to the present application is shown in the flowchart;

[0042] Figure 4 Flow chart of the detection of the safety state of the electric drive system according to the embodiment of the present application. DETAILED DESCRIPTION

[0043] Embodiments of the present application will be described in more detail with reference to the drawings. Although the embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be accurately conveyed to those skilled in the art.

[0044] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0045] The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0046] Please refer to Figure 1 , which shows a structure schematic diagram of a detection device for the safety state of an electric drive system according to an embodiment of the present application. The detection device includes a controller 10, a drive circuit 20 and switching elements. The controller 10 is electrically connected to the drive circuit 20. The switching elements are electrically connected to the drive circuit 20. The switching elements include three upper bridge arms 11 and three lower bridge arms. Each upper bridge arm 11 is connected to a corresponding lower bridge arm 12. The upper bridge arm 11 is electrically connected to a first electrode 31 of a power supply of the electric drive system. The lower bridge arm 12 is electrically connected to a second electrode 32 of the power supply. Three-phase input terminals of a motor 40 of the electric drive system are respectively electrically connected between the upper bridge arm 11 and the corresponding lower bridge arm 12.

[0047] The detection device further includes a first resistor 13 and a second resistor 14. One first resistor 13 is connected in parallel between the two ends of each upper bridge arm 11. One second resistor 14 is connected in parallel between the two ends of each lower bridge arm 12.

[0048] The detection device further includes an upper bridge voltage detector 15 and a lower bridge voltage detector 16. One upper bridge voltage detector 15 is connected in parallel between the two ends of each first resistor 13. One lower bridge voltage detector 16 is connected in parallel between the two ends of each second resistor 14. In actual applications, the upper bridge voltage detector 15 and the lower bridge voltage detector 16 can be voltmeters.

[0049] In the embodiment of the present application, because the controller is electrically connected with the drive circuit, the switching element is electrically connected with the drive circuit, the upper bridge arm is electrically connected with the first electrode of the power supply of the electric drive system, the lower bridge arm is electrically connected with the second electrode of the power supply, and the three-phase input end of the motor of the electric drive system is electrically connected between the upper bridge arm and the corresponding lower bridge arm, so that in the normal working mode of the electric drive system, the controller can control the drive circuit to output the duty cycle of the pulse width modulation (PWM) wave of each bridge arm, so as to alternately turn on / off the upper and lower bridge arms, thereby driving the motor to work.

[0050] In the working mode of the electric drive system, if an overcurrent or overvoltage fault occurs suddenly, because the motor needs to enter a safe state, the control circuit of the controller such as a main control chip or a monitoring chip sends a control instruction to the drive circuit, and finally outputs a control signal for turning on / off each bridge arm, so that the entire electric drive system enters an active short-circuit state or a safe pulse-off state, thereby protecting the motor.

[0051] In the embodiment of the present application, the voltage value of the power supply is known, and the power supply is a direct-current high-voltage power supply.

[0052] The first resistor is connected in parallel between the two ends of the upper bridge arm, and the second resistor is connected in parallel between the two ends of the lower bridge arm, that is, the first resistor is connected between the two ends of the upper bridge arm, and the second resistor is connected between the two ends of the lower bridge arm, so that when the upper bridge arm is controlled to be turned off and the lower bridge arm is controlled to be turned on, the first resistor is short-circuited, the second resistor is used for voltage division of the lower bridge arm, the voltage between the two ends of the first resistor and the voltage between the two ends of the second resistor are obtained, and the power supply voltage is combined, so as to determine whether the upper bridge arm is completely turned off.

[0053] When the lower bridge arm is controlled to be turned off and the upper bridge arm is controlled to be turned on, the second resistor is short-circuited, the first resistor is used for voltage division of the upper bridge arm, the voltage between the two ends of the first resistor and the voltage between the two ends of the second resistor are obtained, and the power supply voltage is combined, so as to determine whether the lower bridge arm is completely turned off.

[0054] When the upper bridge arm and the lower bridge arm are controlled to be turned off, the voltage between the two ends of the first resistor and the voltage between the two ends of the second resistor are obtained, and the power supply voltage is combined, so as to determine whether the upper bridge arm and the lower bridge arm are completely turned off.

[0055] The detection device provided by the embodiment of the present application can identify whether the safety state function of the electric drive system can work normally during the self-checking of the vehicle, so as to ensure that when a fault occurs during the driving of the vehicle, the control circuit can control the drive circuit to truly enter an effective safety state, thereby protecting the electric drive system and ensuring the driving safety of the vehicle system.

[0056] For example, when the upper bridge is actively short-circuited, i.e. the upper bridge arm is turned off and the lower bridge arm is turned on, the voltage across the first resistor should theoretically be 0, and the voltage across the second resistor is the power supply voltage; when the lower bridge is actively short-circuited, i.e. the lower bridge arm is turned off and the upper bridge arm is turned on, the voltage across the second resistor should theoretically be 0, and the voltage across the first resistor is the power supply voltage; when the switch element is in a pulse-off state, the sum of the voltage across the first resistor and the voltage across the second resistor is the power supply voltage, and the ratio of the voltage across the first resistor to the voltage across the second resistor is equal to the ratio of the resistance of the first resistor to the resistance of the second resistor.

[0057] In the embodiment of the application, the upper bridge voltage detector is connected in parallel across the corresponding first resistor, so that the voltage across the second resistor can be obtained when the upper bridge arm is controlled to be turned off; at the same time, the lower bridge voltage detector is connected in parallel across the corresponding second resistor, so that the voltage across the first resistor can be obtained when the lower bridge arm is controlled to be turned off.

[0058] Alternatively, in an embodiment, the resistance of the first resistor is the same as the resistance of the second resistor, so that by comparing whether the voltage across the first resistor when the lower bridge arm is controlled to be turned off and the upper bridge arm is controlled to be turned on is the same as the voltage across the second resistor when the lower bridge arm is controlled to be turned off and the upper bridge arm is controlled to be turned on, and whether the voltage across the second resistor when the lower bridge arm is controlled to be turned off and the upper bridge arm is controlled to be turned on is equal to and close to 0, and whether the voltage across the first resistor is equal to the voltage across the second resistor when the switch element is in a pulse-off state, it can be quickly determined whether the safety state function of the electric drive system can work normally.

[0059] Alternatively, in an embodiment, please continue to refer to Figure 1 The detection device further comprises first voltage dividing resistors 17 and second voltage dividing resistors 18, each of the first resistors 13 is connected in series with a corresponding one of the first voltage dividing resistors 17 and then connected in parallel across the corresponding upper bridge arm 11, each of the second resistors 14 is connected in series with a corresponding one of the second voltage dividing resistors 18 and then connected in parallel across the corresponding lower bridge arm 12, and the resistance of the first voltage dividing resistors 17 is the same as the resistance of the second voltage dividing resistors 18.

[0060] In the above embodiment, since the first resistor needs to be protected by the first voltage dividing resistor and the second resistor needs to be protected by the second voltage dividing resistor, the resistance of the first voltage dividing resistor needs to be greater than the resistance of the first resistor, and the resistance of the second voltage dividing resistor needs to be greater than the resistance of the second resistor, so that the voltage across the first resistor can be detected by a less range upper bridge voltage detector, and the voltage across the second resistor can be detected by a less range lower bridge voltage detector, and the voltage detection accuracy is improved.

[0061] Meanwhile, in the above embodiment, the resistance of the first voltage dividing resistor is the same as the resistance of the second voltage dividing resistor, which ensures that by comparing whether the voltage across the first resistor when the upper bridge is actively short-circuited is the same as the voltage across the second resistor when the lower bridge is actively short-circuited and close to zero, and comparing whether the voltage across the second resistor when the upper bridge is actively short-circuited is the same as the voltage across the second resistor when the lower bridge is actively short-circuited, and comparing whether the voltage across the first resistor is the same as the voltage across the second resistor when the switching element is in a pulse-off state, it can be quickly determined whether the electric drive system safety state function can work normally.

[0062] Specifically, when each of the upper bridge arms is controlled to be off and each of the lower bridge arms is controlled to be on, the voltage across each of the first resistors is obtained as a first voltage division, and the voltage across each of the second resistors is obtained as a second voltage division; when each of the lower bridge arms is controlled to be off and each of the upper bridge arms is controlled to be on, the voltage across each of the first resistors is obtained as a third voltage division, and the voltage across each of the second resistors is obtained as a fourth voltage division; when each of the upper bridge arms and each of the lower bridge arms is controlled to be off, the voltage across each of the first resistors is obtained as a fifth voltage division, and the voltage across each of the second resistors is obtained as a sixth voltage division, if the resistance of the first voltage dividing resistor is R1, the resistance of the first resistor is R2, and the power supply voltage is Vdc, correspondingly, the resistance of the second voltage dividing resistor is also R1, and the resistance of the second resistor is also R2, theoretically, the first voltage division = the fourth voltage division = 0, the second voltage division = the third voltage division = Vdc x R2 / (R1+R2), the fifth voltage division = the sixth voltage division = Vdc x R2 / 2(R1+R2), if all the above relationships are true, it can be determined that each bridge arm can normally execute the on-off signal of the drive circuit, and the electric drive system can be controlled to successfully enter the safety state when a fault occurs.

[0063] Optionally, in an embodiment, V0=Vdc x R2 / (R1+R2) is set; V1=k1 x V0; V2=C; V3=k2 x V0 / 2; V4=k1 x V0 / 2; C is a constant greater than 0 and close to 0, k1 is a coefficient less than 1 and close to 1, and k2 is a coefficient greater than 1 and close to 1; if the first and fourth voltage divisions are both less than V2, the second and third voltage divisions are both greater than V1, the average of the fifth and sixth voltage divisions is greater than V4 and less than V3, and the bus current Idc is 0 and the motor speed is approximately 0, it is indicated that each bridge arm can normally execute the on-off signal of the drive circuit, and the electric drive system can successfully enter the safe state when a fault occurs. In the embodiment, each comparison value leaves a certain margin compared with the theoretical value, so that it is more accurate and reliable in actual application.

[0064] In actual application, the values of k1, k2 and C can be adjusted according to the actual circuit detection result. For example, C can be set to 0.5, k1 can be set to 0.9, and k2 can be set to 1.1.

[0065] Optionally, in an embodiment, the switching element is an insulated gate bipolar transistor (IGBT), one first resistor is connected in parallel on each upper bridge arm of the insulated gate bipolar transistor, and each first resistor is connected in series with one first voltage division resistor; one second resistor is connected in parallel on each lower bridge arm of the insulated gate bipolar transistor, and each second resistor is connected in series with one second voltage division resistor. That is, the resistance voltage division detection circuit is added to the six bridge arms of the IGBT, that is, the first voltage division resistor and the first resistor are added in series to the rear stage of each upper bridge arm, the second voltage division resistor and the second resistor are added in series to the rear stage of each lower bridge arm, the resistance values of the first voltage division resistor and the second voltage division resistor are equal, and the resistance values of the first resistor and the second resistor are equal. The on / off state of the six bridge arms of the IGBT is determined by the voltage values at the two ends of the first resistor and the second resistor, so that whether the electric drive system can successfully enter the safe state when a fault occurs is detected.

[0066] As shown in FIG. 1, Figure 1 The three upper bridge arms 11 of the IGBT are respectively a U-phase upper bridge arm UH, a V-phase upper bridge arm UV and a W-phase upper bridge arm UW, and the lower bridge arms 12 corresponding to the upper bridge arms 11 are respectively a U-phase lower bridge arm UL, a V-phase lower bridge arm VL and a W-phase lower bridge arm WL. Each bridge arm is driven by a drive circuit, and when the electric drive system works normally, the controller controls the duty cycle of the six bridge arm PWM waves output by the drive circuit, so that the upper and lower bridge arms are alternately turned on / off, thereby driving the motor to work.

[0067] In practical applications, the motor is a permanent magnet synchronous motor, and the power supply is a high-voltage direct current power supply, which can drive the motor to operate through the rectification or inversion of IGBT.

[0068] Optionally, in an embodiment, the controller is electrically connected with each of the upper bridge voltage detector and the lower bridge voltage detector, so that the voltage value of the first resistor detected by the upper bridge voltage detector can be directly sent to the controller, and the voltage value of the second resistor detected by the lower bridge voltage detector can be directly sent to the controller, thereby facilitating the controller to determine whether each bridge arm can normally perform the turn-off operation.

[0069] In practical applications, please refer to Figure 2 , which shows the control structure schematic diagram of the electric drive system in the embodiment of the present application. As shown in Figure 2 , the control structure includes a drive circuit and a switching element, the switching element is electrically connected with the drive circuit, the switching element includes a U-phase upper bridge arm UH, a V-phase upper bridge arm VH, and a W-phase upper bridge arm WH, and a U-phase lower bridge arm UL, a V-phase lower bridge arm VL, and a W-phase lower bridge arm WL connected with each of the upper bridge arms, respectively, the upper bridge arms UH, VH, and WH are electrically connected to the positive electrode of the power supply of the electric drive system, the lower bridge arms UL, VL, and WL are electrically connected to the negative electrode of the power supply, the motor of the electric drive system is electrically connected between the upper bridge arms and the lower bridge arms, and each of the bridge arms is driven by a drive circuit, when the electric drive system normally works, the controller controls the duty cycle of the six bridge arm PWM waves output by the drive circuit, so that the upper and lower bridge arms are alternately turned on / off, thereby driving the motor to work.

[0070] Another object of the present application is to provide a detection method for the safe state of an electric drive system, which is applied to a controller, the controller is electrically connected with a drive circuit, the drive circuit is electrically connected with a switching element, the switching element includes three upper bridge arms and three lower bridge arms, each of the upper bridge arms is connected with one of the lower bridge arms, the upper bridge arms are electrically connected to the first electrode of the power supply of the electric drive system, the lower bridge arms are electrically connected to the second electrode of the power supply, the three-phase input end of the motor of the electric drive system is electrically connected between the upper bridge arms and the corresponding lower bridge arms, one first resistor is connected in parallel between the two ends of each of the upper bridge arms, and one second resistor is connected in parallel between the two ends of each of the lower bridge arms; one upper bridge voltage detector is connected in parallel between the two ends of each of the first resistors, and one lower bridge voltage detector is connected in parallel between the two ends of each of the second resistors; wherein, please refer to Figure 3 , which shows the flowchart of the detection method for the safe state of the electric drive system provided by the embodiment of the present application, the method includes steps S100-S400.

[0071] In the embodiment of the present application, the first resistor is connected between the two ends of the upper bridge arm, and the second resistor is connected between the two ends of the lower bridge arm. When the upper bridge arm is controlled to be turned off and the lower bridge arm is controlled to be turned on, the first resistor is short-circuited, and the lower bridge arm is divided by the second resistor. By obtaining the voltage across each first resistor and the voltage across each second resistor, and combining the power supply voltage, it can be determined whether the upper bridge arm is completely turned off.

[0072] When the lower bridge arm is controlled to be turned off and the upper bridge arm is controlled to be turned on, the second resistor is short-circuited, and the upper bridge arm is divided by the first resistor. By obtaining the voltage across each first resistor and the voltage across each second resistor, and combining the power supply voltage, it can be determined whether the lower bridge arm is completely turned off.

[0073] When the upper bridge arm and the lower bridge arm are both controlled to be turned off, by obtaining the voltage across each first resistor and the voltage across each second resistor, and combining the power supply voltage, it can be determined whether the upper bridge arm and the lower bridge arm are both completely turned off.

[0074] Step S100, when the electric drive system is started, the drive circuit outputs a pulse width modulation wave to control each of the upper bridge arms and / or each of the lower bridge arms to be turned off.

[0075] In the above step S100, when the electric drive system is started, the controller first sends a control instruction to control the drive circuit to output a pulse width modulation wave, and then controls the upper bridge to enter an active short-circuit state and / or controls the lower bridge to enter an active short-circuit state. In the case where each upper bridge arm and the corresponding lower bridge arm has multiple ones, the above step S100 controls all upper bridge arms to be turned off and all lower bridge arms to be turned on, or all lower bridge arms to be turned off and all upper bridge arms to be turned on, or all lower bridge arms to be turned off and all upper bridge arms to be turned off.

[0076] Step S200, when each of the upper bridge arms is controlled to be turned off and each of the lower bridge arms is controlled to be turned on, the first voltage division on each of the first resistors is obtained by the upper bridge voltage detector, and the second voltage division on each of the second resistors is obtained by the lower bridge voltage detector.

[0077] In the above step S200, after the drive circuit sends a turn-off signal to the upper bridge arm, the voltage across each first resistor is obtained, and the voltage across each second resistor is obtained. At this time, the voltage across each first resistor should be 0 in theory, and the voltage across each second resistor is the power supply voltage.

[0078] Step S300, when each of the lower bridge arms is controlled to be off and each of the upper bridge arms is controlled to be on, a third voltage division across each of the first resistors is obtained by the upper bridge voltage detector, and a fourth voltage division across each of the second resistors is obtained by the lower bridge voltage detector.

[0079] In step S300, after the driving circuit sends the off signal to the lower bridge arms, the voltage across each of the first resistors is obtained, and the voltage across each of the second resistors is obtained. At this time, the voltage across each of the second resistors should be 0 in theory, and the voltage across each of the first resistors is the voltage of the power supply.

[0080] Step S400, when each of the upper bridge arms and each of the lower bridge arms is controlled to be off, a fifth voltage division across each of the first resistors is obtained by the upper bridge voltage detector, and a sixth voltage division across each of the second resistors is obtained by the lower bridge voltage detector.

[0081] In step S400, after the driving circuit sends the off signal to the switch element, the voltage across each of the first resistors is obtained, and the voltage across each of the second resistors is obtained. At this time, the sum of the voltage across each of the first resistors and the voltage across the corresponding second resistor is the voltage of the power supply, and the ratio of the voltage across each of the first resistors and the voltage across the corresponding second resistor is equal to the ratio of the resistance of the first resistor and the resistance of the corresponding second resistor.

[0082] Step S500, according to the first voltage division, the second voltage division, the third voltage division, the fourth voltage division, the fifth voltage division and the sixth voltage division, the safety state of the electric driving system is determined.

[0083] In step S500, because the voltages across the first resistors and the second resistors in different safety states are completely different, the state of each bridge arm at present can be determined according to the differences of each of the first voltage division, each of the second voltage division, each of the third voltage division, each of the fourth voltage division, each of the fifth voltage division and each of the sixth voltage division, and then it is detected whether the electric driving system can successfully enter the safety state when a fault occurs.

[0084] Compared with the prior art, the detection method of the safety state of the electric driving system has the following advantages:

[0085] A first resistor is connected in parallel between both ends of each upper bridge arm of the switching element, and a second resistor is connected in parallel between both ends of each lower bridge arm of the switching element. By adding a resistor voltage dividing circuit at the rear stage of the upper bridge arm and the lower bridge arm, the safety state is determined by the voltage values at both ends of the resistors, the driving circuit can be directly detected whether it truly performs active short-circuit or safety pulse off operation according to the actual instruction of the controller, which is simple and easy to implement, and does not produce unintended torque. During the detection process, no current enters the motor, so as to avoid vehicle shaking and ensure safety and reliability.

[0086] Optionally, in an embodiment, the detection method provided by the embodiment of the present application, the resistance value of the first resistor is the same as the resistance value of the second resistor, and the step S500 comprises:

[0087] If each first voltage division and each third voltage division are less than a first threshold value, each second voltage division and each fourth voltage division are greater than a second threshold value, and the average of each fifth voltage division and each sixth voltage division is greater than a third threshold value and less than a fourth threshold value, it is determined that the electric driving system is in a safety state.

[0088] In the above embodiment, the resistance value of each first resistor is the same as the resistance value of each second resistor, so that the voltage division on the first resistor when the upper bridge is actively short-circuited is the same as the voltage division on the corresponding second resistor when the lower bridge is actively short-circuited. Because when the upper bridge arm is off and the lower bridge arm is on, the upper bridge arm and the wire also have a certain resistance, resulting in that the first voltage division is slightly greater than 0, and also making the second voltage division slightly less than the power supply voltage; similarly, when the upper bridge arm is on and the lower bridge arm is off, the lower bridge arm and the wire also have a certain resistance, resulting in that the fourth voltage division is slightly greater than 0, and also making the third voltage division slightly less than the power supply voltage; at the same time, when the upper bridge arm is off and the lower bridge arm is off, the upper bridge arm, the lower bridge arm and the wire also have a certain resistance, resulting in that the average of the fifth voltage division and the sixth voltage division fluctuates around half of the power supply voltage; the above-mentioned first threshold value is a voltage threshold value for determining whether the upper bridge arm and the lower bridge arm can respond to the on instruction, the above-mentioned second threshold value is a voltage threshold value for determining whether the upper bridge arm and the lower bridge arm can respond to the off instruction, and the above-mentioned third threshold value and the fourth threshold value are voltage threshold values for determining whether the upper bridge arm and the lower bridge arm can simultaneously respond to the off instruction.

[0089] In the above embodiment, if each first voltage division and each third voltage division is less than the first threshold value, it indicates that each upper bridge arm and each lower bridge arm can be independently turned off; if each second voltage division and each fourth voltage division is greater than the second threshold value, it indicates that each upper bridge arm and each lower bridge arm can be independently turned on; if the average of each fifth voltage division and each sixth voltage division is greater than the third threshold value and less than the fourth threshold value, it indicates that the upper bridge arm and the lower bridge arm can be simultaneously turned off; thus, it can be determined that the electric drive system is in a safe state. In the embodiment, each comparison value leaves a certain margin compared with the theoretical value, so that it is more accurate and reliable in actual application

[0090] Optionally, in an embodiment, in the detection method provided by the embodiment of the present application, each first resistor and a corresponding first voltage division resistor are connected in series and then connected in parallel between the two ends of the corresponding upper bridge arm, and each second resistor and a corresponding second voltage division resistor are connected in series and then connected in parallel between the two ends of the corresponding lower bridge arm, the resistance value of the first voltage division resistor is the same as the resistance value of the second voltage division resistor.

[0091] The first threshold value is V1, the second threshold value is V2, the third threshold value is V3, and the fourth threshold value is V4; wherein, V0=Vdc×R2 / (R1+R2); V1=k1×V0; V2=C; V3=k2×V0 / 2; V4=k1×V0 / 2; C is a constant greater than 0 and close to 0, k1 is a coefficient less than 1 and close to 1, k2 is a coefficient greater than 1 and close to 1, Vdc is the voltage of the power supply of the electric drive system, R1 is the resistance value of the first voltage division resistor, and R2 is the resistance value of the first resistor.

[0092] In the embodiment, the first resistor is protected by the first voltage division resistor, and the second resistor is protected by the second voltage division resistor, the resistance value of the first voltage division resistor is greater than the resistance value of the first resistor, and the resistance value of the second voltage division resistor is greater than the resistance value of the second resistor, so that the voltage across the first resistor can be detected by using a smaller range upper bridge voltage detector, and the voltage across the second resistor can be detected by using a smaller range lower bridge voltage detector, thereby improving the voltage detection accuracy.

[0093] Meanwhile, in the embodiment, each threshold value leaves a certain margin compared with the corresponding theoretical value, so that it is more accurate and reliable in actual application.

[0094] Optionally, in an embodiment, the method further includes steps S401-S403:

[0095] Step S401, if each of the first partial pressure is not less than the first threshold value, or each of the third partial pressure is not less than the first threshold value, or each of the second partial pressure is not greater than the second threshold value, or each of the fourth partial pressure is not greater than the second threshold value, or each of the fifth partial pressure and the average of each of the sixth partial pressure does not satisfy greater than the third threshold value and less than the fourth threshold value, the error number is added by 1.

[0096] In the step S401, after the safety state detection of the electric drive system is performed once, if at least one of the following conditions occurs: the first partial pressure is not less than the first threshold value, the third partial pressure is not less than the first threshold value, the second partial pressure is not greater than the second threshold value, the fourth partial pressure is not greater than the second threshold value, and the average of the fifth partial pressure and the sixth partial pressure does not satisfy greater than the third threshold value and less than the fourth threshold value, it indicates that the switching element cannot guarantee that the electric drive system can successfully enter the safety state when a fault occurs. Considering that the detection condition is prone to errors and accidental conditions, the error number is added by 1, and the safety state detection of the electric drive system is continued.

[0097] Step S402, determining whether the error number reaches a preset number threshold.

[0098] In the step S402, the preset number threshold is a number threshold for determining whether the condition is a detection error. In the step S402, the condition is determined to be a detection error by accumulating the number of times that the switching element cannot guarantee that the electric drive system enters the safety state. In practical applications, the preset number threshold can be set as needed, for example, 3, 4, or 5.

[0099] Step S403, if the error number reaches the preset number threshold, it is determined that the electric drive system is not in the safety state.

[0100] In the step S403, if the number of times that the switching element cannot guarantee that the electric drive system enters the safety state reaches the preset number threshold, it indicates that the switching element has a shutdown response failure, and it is determined that the electric drive system is not in the safety state.

[0101] In the above embodiment, by setting the preset number threshold and accumulating the number of times that the switching element cannot guarantee that the electric drive system enters the safety state, accidental errors can be avoided, and the detection accuracy can be prompted.

[0102] Optionally, in an embodiment, the method further comprises step S404 after step S402:

[0103] Step S404, if the error number does not reach the preset number threshold, re-enter the step of controlling the driving circuit to output the pulse width modulation wave to control the upper bridge arm and / or the lower bridge arm to be off.

[0104] In step S404, if the number of times that the detected switch element cannot ensure the electric drive system to enter the safe state is less than the preset number threshold, the safe state detection of the electric drive system is continued to avoid detection errors.

[0105] Optionally, in an embodiment, after step S500, step S600 is further included:

[0106] Step S600, the error number is cleared.

[0107] In the embodiment, after it is determined that the switch element can ensure the electric drive system to successfully enter the safe state when a fault occurs, the error number is cleared to facilitate the next time the motor is started and the safe state detection is performed, and the number of times that the switch element cannot ensure the electric drive system to enter the safe state is accumulated.

[0108] In actual application, when the resistance values of the first resistors and the second resistors are equal, the resistance values of the first voltage division resistors and the second voltage division resistors are equal, and the switch element has six bridge arms, please refer to Figure 4 , a flow chart of the detection execution of the safe state of the electric drive system proposed by the embodiment of the application is shown.

[0109] As shown in Figure 4 , in step S411, when the motor is powered on, the controller first issues a safe state detection instruction, and then the control circuit generates and issues a control instruction for controlling the off state of the switch element, at this time, the error number is 0, and then step S412 is entered.

[0110] In step S412, it is determined whether the control circuit issues a low-side ASC instruction, if yes, step S413 is entered, otherwise, step S414 is entered.

[0111] In step S413, it is determined whether the voltage across each first resistor is greater than a first threshold value and the voltage across each second resistor is less than a second threshold value.

[0112] In step S414, it is determined whether the control circuit issues a high-side ASC instruction, if yes, step S415 is entered, otherwise, step S416 is entered.

[0113] In step S415, it is determined whether the voltage across each second resistor is greater than a first threshold value and the voltage across each first resistor is less than a second threshold value.

[0114] In step S416, it is determined whether the voltage across each first resistor and the average of the voltage across each second resistor is greater than the third threshold value and less than the fourth threshold value, and the bus current is close to 0, and the motor speed is less than the preset speed threshold value;

[0115] In step S417, if the determination results of step S413, step S415 and step S416 are all yes, that is, whether the conditions in step S413, step S415 and step S416 can be met at the same time, step S421 is entered, otherwise step S418 is entered;

[0116] In step S418, it is determined whether the error number Counter is less than the number threshold value; if the error number Counter is less than the number threshold value Con1, step S419 is entered, and the Counter is incremented by 1, and then re-entered into step S411; if the error number Counter is not less than the number threshold value Con1, step S420 is entered, and the safety state error is determined, that is, the electric drive system cannot successfully enter the safety state when a fault occurs;

[0117] In step S421, the safety state detection is ended, and the error number is cleared.

[0118] Still another purpose of the present application is to provide a vehicle, wherein the vehicle further comprises the detection device of the safety state of the electric drive system as described above.

[0119] The detection method of the safety state of the electric drive system, the vehicle and the detection device of the safety state of the electric drive system have the same advantages as the prior art, and will not be described here

[0120] In summary, the detection method, device and vehicle of the safety state of the electric drive system provided by the present application, the detection device comprises first resistors and second resistors, the first resistors are connected in parallel between each upper bridge arm of the switching element, and the second resistors are connected in parallel between each lower bridge arm of the switching element; the detection device further comprises an upper bridge voltage detector and a lower bridge voltage detector; the upper bridge voltage detector is connected in parallel across each first resistor, and the lower bridge voltage detector is connected in parallel across each second resistor. By increasing the resistance voltage dividing circuit in the upper bridge arm and the lower bridge arm, the safety state is determined by the different voltage values across the resistors, the driving circuit can be directly detected whether the actual instruction of the controller is truly active short-circuit or safety pulse off operation, which is simple and easy to implement, and will not produce unexpected torque, and current will not enter the motor during the detection process, so as to avoid vehicle shaking and ensure safety and reliability.

[0121] Those skilled in the art can clearly understand the specific working process of the system, device and unit described above for the convenience and brevity of description, which can refer to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0122] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0123] The above only describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which shall be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A device for detecting the safety status of an electric drive system, characterized in that, The system includes a controller, a drive circuit, and a switching element. The controller is electrically connected to the drive circuit, and the switching element is also electrically connected to the drive circuit. The switching element includes three upper bridge arms and three lower bridge arms. Each upper bridge arm is connected to one lower bridge arm. Each upper bridge arm is electrically connected to the first electrode of the power supply of the electric drive system, and each lower bridge arm is electrically connected to the second electrode of the power supply. The three-phase input terminals of the motor of the electric drive system are electrically connected between the upper bridge arms and the corresponding lower bridge arms. The detection device further includes a first resistor and a second resistor. One first resistor is connected in parallel between the two ends of each upper bridge arm, and one second resistor is connected in parallel between the two ends of each lower bridge arm. The detection device further includes an upper bridge voltage detector and a lower bridge voltage detector; one upper bridge voltage detector is connected in parallel across each of the first resistors, and one lower bridge voltage detector is connected in parallel across each of the second resistors; The controller is used to control the drive circuit to output a pulse width modulation wave in order to control each of the upper bridge arms and / or each of the lower bridge arms to turn off. The upper bridge voltage detector is used to acquire the voltage across the first resistor when each of the upper bridge arms and / or each of the lower bridge arms is turned off, and the lower bridge voltage detector is used to acquire the voltage across the second resistor when each of the upper bridge arms and / or each of the lower bridge arms is turned off.

2. The detection device according to claim 1, characterized in that, The resistance value of the first resistor is the same as the resistance value of the second resistor.

3. The detection device according to claim 2, characterized in that, The detection device further includes a first voltage divider resistor and a second voltage divider resistor. Each first resistor is connected in series with a corresponding first voltage divider resistor and then connected in parallel between the two ends of the upper bridge arm. Each second resistor is connected in series with a corresponding second voltage divider resistor and then connected in parallel between the two ends of the lower bridge arm. The resistance values ​​of the first voltage divider resistor and the second voltage divider resistor are the same.

4. The detection device according to claim 3, characterized in that, The switching element is an insulated gate bipolar transistor.

5. The detection device according to claim 1, characterized in that, The controller is electrically connected to each of the upper bridge voltage detectors and each of the lower bridge voltage detectors.

6. A method for detecting the safety status of an electric drive system, characterized in that, The system is applied to a controller, which is electrically connected to a drive circuit. The drive circuit is electrically connected to a switching element, which includes three upper bridge arms and three lower bridge arms. Each upper bridge arm is connected to one lower bridge arm. Each upper bridge arm is electrically connected to the first electrode of the power supply of the electric drive system, and each lower bridge arm is electrically connected to the second electrode of the power supply. The three-phase input terminals of the electric drive system motor are electrically connected between the upper bridge arms and the corresponding lower bridge arms. A first resistor is connected in parallel between the two ends of each upper bridge arm, and a second resistor is connected in parallel between the two ends of each lower bridge arm. An upper bridge voltage detector is connected in parallel between the two ends of each first resistor, and a lower bridge voltage detector is connected in parallel between the two ends of each second resistor. The method includes: When the electric drive system starts, the drive circuit is controlled to output a pulse width modulation wave to control the upper bridge arm and / or the lower bridge arm to turn off. When controlling each of the upper bridge arms to turn off and controlling each of the lower bridge arms to turn on, the first voltage division on each of the first resistors is obtained through the upper bridge voltage detector, and the second voltage division on each of the second resistors is obtained through the lower bridge voltage detector; When controlling each of the lower bridge arms to turn off and controlling each of the upper bridge arms to turn on, the third voltage division on each of the first resistors is obtained through the upper bridge voltage detector, and the fourth voltage division on each of the second resistors is obtained through the lower bridge voltage detector. When all the upper bridge arms and all the lower bridge arms are turned off, the fifth voltage division on each of the first resistors is obtained through the upper bridge voltage detector, and the sixth voltage division on each of the second resistors is obtained through the lower bridge voltage detector. The safety status of the electric drive system is determined based on each of the first voltage divider, each of the second voltage divider, each of the third voltage divider, each of the fourth voltage divider, each of the fifth voltage divider, and each of the sixth voltage divider.

7. The detection method according to claim 6, characterized in that, The resistance values ​​of each of the first resistors are the same as the resistance values ​​of each of the second resistors. Determining the safety state of the electric drive system based on each of the first voltage divider, each of the second voltage divider, each of the third voltage divider, each of the fourth voltage divider, each of the fifth voltage divider, and each of the sixth voltage divider includes: If each of the first voltage dividers and each of the third voltage dividers is less than the first threshold, and each of the second voltage dividers and each of the fourth voltage dividers is greater than the second threshold, and the average of each of the fifth voltage dividers and each of the sixth voltage dividers is greater than the third threshold and less than the fourth threshold, then the electric drive system is determined to be in a safe state.

8. The detection method according to claim 7, characterized in that, Each of the first resistors is connected in series with its corresponding first voltage divider resistor and then connected in parallel between the two ends of the corresponding upper bridge arm. Each of the second resistors is connected in series with its corresponding second voltage divider resistor and then connected in parallel between the two ends of the corresponding lower bridge arm. The resistance values ​​of the first voltage divider resistor and the second voltage divider resistor are the same. The first threshold is V1, the second threshold is V2, the third threshold is V3, and the fourth threshold is V4; wherein, V0 = Vdc × R2 / (R1 + R2); V1 = k1 × V0; V2 = C; V3 = k2 × V0 / 2; V4 = k1 × V0 / 2; C is a constant greater than 0 and close to 0, k1 is a coefficient less than 1 and close to 1, k2 is a coefficient greater than 1 and close to 1, Vdc is the voltage of the power supply of the electric drive system, R1 is the resistance value of the first voltage divider resistor, and R2 is the resistance value of the first resistor.

9. The detection method according to claim 7, characterized in that, The method further includes: If none of the first voltages are less than the first threshold, or none of the third voltages are less than the first threshold, or none of the second voltages are greater than the second threshold, or none of the fourth voltages are greater than the second threshold, or the average of the fifth voltages and the sixth voltages does not satisfy the condition of being greater than the third threshold and less than the fourth threshold, then the error count is incremented by 1. Determine whether the number of errors has reached a preset threshold. If the number of errors reaches the preset threshold, the electric drive system is determined to be in an unsafe state.

10. A vehicle, characterized in that, It includes a detection device for the safety status of an electric drive system as described in any one of claims 1 to 5.

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