Fault detection circuit, motor controller, power system and electric automobile

Abstract

The invention provides a fault detection circuit, a motor controller, a power system and an electric automobile, the fault detection circuit is connected between a three-phase power line and a control processing unit, each fault detection circuit comprises three detection sub-circuits, and whether faults exist on the three phases or not is judged by detecting the voltage on each phase. The problem that whether the three-phase power line of the motor is insulated or not cannot be judged is solved.

Description

Technical Field

[0001] The present application relates to the field of electric vehicles, and in particular to a fault detection circuit, a motor controller, a power system and an electric vehicle. Background Art

[0002] The motor of electric vehicles (including pure electric vehicles) generally adopts permanent magnet synchronous motor. There are two parts of batteries on the whole vehicle, namely the power high-voltage battery (generally 300V-800V) that provides power output, and the weak-current battery (generally 12V or 24V) that controls the power supply. The driver and motor on the whole vehicle are generally connected to the vehicle shell by grounding, and the ground of the control power supply is also connected to the shell. Generally, the battery end will sample the insulation resistance to confirm the insulation resistance of the positive and negative ends of the battery to the shell, so as to judge whether the insulation of the whole vehicle is normal. However, it is impossible to judge whether there is a problem with the insulation of the three-phase power line of the motor by this method. Often, after the driver opens the tube, it falsely reports a drive fault or overcurrent fault, but in fact it is caused by the insulation problem of the motor, which makes it difficult to troubleshoot the problem. At the same time, the drive motor in this case also has the risk of driver short circuit, which may cause damage to the IGBT (insulated gate bipolar transistor). Therefore, it is necessary to judge whether there is an abnormality in the insulation of the three-phase line of the motor to the shell before driving and controlling the motor.

[0003] To address the above problems, no effective solution has been proposed yet. Summary of the invention

[0004] In view of this, the present application proposes a fault detection circuit, a motor controller, a power system and an electric vehicle, wherein a fault detection circuit is connected between the three-phase power line and the control processing unit, and each fault detection circuit includes three detection subcircuits, and by detecting the voltage on each phase, it is determined whether there is a fault on the three phases. The problem of being unable to determine whether there is an insulation problem with the three-phase power line of the motor is solved.

[0005] According to one aspect of the present application, a fault detection circuit for a power system of an electric vehicle is provided, wherein:

[0006] The fault detection circuit comprises three identical detection subcircuits, the input ends of the three detection subcircuits are respectively connected to the three-phase power lines of the motor drive circuit of the power system that provide three-phase power to the motor, and the output ends of the three detection subcircuits are respectively connected to the control processing unit of the power system;

[0007] Each detection subcircuit includes:

[0008] Operational amplifier;

[0009] A first resistor and a second resistor are connected in series between the input end of the detection subcircuit and the same-direction input end of the operational amplifier, and a reference voltage V is connected between the first resistor and the second resistor. ref ;

[0010] A third resistor and a fourth resistor, wherein the third resistor and the fourth resistor are connected in series between the input end of the detection subcircuit and the inverting input end of the operational amplifier, and connected to the output end of the operational amplifier through a fifth resistor between the third resistor and the fourth resistor;

[0011] The output end of the operational amplifier is connected to the control processing unit of the power system as the output end of the detection subcircuit.

[0012] Optionally,

[0013] The values ​​of the first resistor and the third resistor are greater than 100 MΩ.

[0014] Optionally,

[0015] The first resistor and the third resistor each include a plurality of resistors connected in series.

[0016] Optionally,

[0017] A first capacitor is connected to ground between the first resistor and the second resistor, and a second capacitor is connected to ground between the second resistor and the non-inverting input terminal of the operational amplifier;

[0018] and / or,

[0019] A third capacitor is connected to ground between the third resistor and the fourth resistor, and a fourth capacitor is connected between the fourth resistor and the inverting input terminal of the operational amplifier to between the third resistor and the fifth resistor.

[0020] and / or,

[0021] A sixth resistor is connected to the output terminal of the operational amplifier.

[0022] Optionally,

[0023] Reference voltage V ref Provided by the weak-current battery in the power system after conversion.

[0024] Optionally,

[0025] Reference voltage V ref The value should be below 3V.

[0026] Optionally,

[0027] The motor controller comprises a motor drive circuit, a control processing unit and a fault detection circuit as described above;

[0028] The motor drive circuit comprises three switch bridge arms, both ends of each switch bridge arm are used to receive the input voltage provided by the power battery, each switch bridge arm comprises an upper bridge arm switch tube and a lower bridge arm switch tube, and the midpoints of the three switch bridge arms respectively provide three-phase power to the three-phase winding of the motor through the three-phase power line to drive the motor to rotate;

[0029] The input ends of the three detection subcircuits of the fault detection circuit are respectively connected to the three-phase power line, and the output ends of the three detection subcircuits are respectively connected to the control processing unit;

[0030] Based on the fault detection circuit, the control processing unit is used to:

[0031] In response to the high voltage power-on and the initial state being normal, one of the switch tubes in the three switch bridge arms is respectively turned on and then turned off, so as to respectively determine the three-phase voltages Vo_U, Vo_V, and Vo_W from the output ends of the three detection sub-circuits;

[0032] Based on the insulation resistance value Rn of the positive terminal of the power battery busbar, the insulation resistance value Rp of the negative terminal of the power battery busbar, Vo_U, Vo_V, Vo_W, V ref , a fifth resistor, and the first resistor and the second resistor or the third resistor and the fourth resistor, and calculate the resistance values ​​Rx_u, Rx_v, and Rx_w of the three-phase power line to the housing respectively;

[0033] When at least one of Rx_u, Rx_v, and Rx_w is less than a predetermined threshold, it is determined to be a three-phase insulation fault of the motor power line, and fault processing is performed.

[0034] Optionally,

[0035] The motor drive circuit should be powered on and in a normal initial state, including:

[0036] In response to high voltage power-on, when the switch tubes in the three switch bridge arms are all turned off, the initial three-phase voltages are respectively determined from the output ends of the three detection sub-circuits;

[0037] When the initial three-phase voltages are respectively ref If the difference is within the preset range, it is judged that the initialization is normal.

[0038] Optionally,

[0039] The control processing unit obtains Rn and Rp from the vehicle controller VCU.

[0040] Optionally,

[0041] Sending a control signal to the motor drive circuit to control the on and off of the switch tubes in the three switch bridge arms;

[0042] According to the on and off conditions of the switch tube, based on the calculated Rx_u, Rx_v, and Rx_w, the theoretical values ​​of the three-phase voltages at the output ends of the operational amplifiers in the three detection sub-circuits are calculated;

[0043] Determine the actual values ​​of the three-phase voltages from the output terminals of the operational amplifiers in the three detection subcircuits respectively;

[0044] When the difference between the theoretical value and the actual value of the corresponding phase voltage is greater than a predetermined threshold, it is determined to be a switch tube failure and fault processing is performed.

[0045] According to another aspect of the present application, a power system of an electric vehicle is provided, comprising:

[0046] A motor and a motor controller as described above.

[0047] According to another aspect of the present application, there is provided an electric vehicle, comprising:

[0048] The power battery and the power system as described above, the power battery supplies power to the power system.

[0049] The present application proposes a fault detection circuit, a motor controller, a power system and an electric vehicle, wherein a fault detection circuit is connected between the three-phase power line and the control processing unit, and each fault detection circuit includes three detection sub-circuits, and by detecting the voltage on each phase, it is determined whether there is a fault on the three phases. The solution of the present application can accurately determine whether there is a fault in the three-phase power line of the motor without falsely reporting other faults, so that the driver can be protected in advance, ensuring the safety of the motor controller and the whole vehicle, and the circuit is simple and easy to operate, without the need to use isolation optocouplers for isolation processing of strong and weak electricity, and the cost is low.

[0050] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0052] Figure 1 A schematic diagram showing a partial frame of an electric vehicle according to the present application;

[0053] Figure 2 A schematic diagram showing an embodiment of a phase detection subcircuit of a fault detection circuit for a power system of an electric vehicle of the present application is shown;

[0054] Figure 3 A schematic diagram showing an embodiment of a reference voltage generating circuit of the present application is shown;

[0055] Figure 4 A schematic diagram showing an embodiment of a process for determining a three-phase insulation fault of a motor power line of a power system of an electric vehicle according to the present application;

[0056] Figure 5 A schematic diagram showing an embodiment of a switch tube fault judgment process for a power system of an electric vehicle of the present application;

[0057] Figure 6 A schematic diagram showing an embodiment of a power system for an electric vehicle of the present application is shown;

[0058] Figure 7 A schematic diagram showing an embodiment of a phase detection subcircuit of a fault detection circuit for a power system of an electric vehicle of the present application is shown;

[0059] Figure 8 A schematic diagram of an embodiment of a detection and protection process based on a fault detection circuit is shown. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0061] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0062] Figure 1 A schematic diagram of a partial frame of an electric vehicle according to the present application is shown.

[0063] As shown in the figure, the electric vehicle at least includes a power system 11 and a power battery 12, and the power battery 12 at least supplies power to the power system 11. The power system 11 is also called a powertrain, and at least includes a motor 111 and a motor controller 112, and the motor controller 112 at least controls the rotation of the motor 111. The motor controller usually uses a pulse width modulation (PWM) signal to control the conduction or disconnection of multiple power switch tubes to change the frequency and voltage amplitude of the output AC power to achieve precise control of the motor speed. The motor controller is not limited to controlling the rotation of the motor, but can also include control of other functions in the electric vehicle.

[0064] The motor controller 112 includes at least a control processing unit 1121 and a motor drive circuit 1122. The control processing unit 1121 is, for example, an MCU (Micro-Controller Unit), which is a very critical component in an electric vehicle and is responsible for receiving vehicle driving control instructions from the vehicle control system and converting the high-voltage direct current of the power battery into alternating current to drive the motor to output a specified torque and speed, thereby driving the vehicle. The control processing unit 1121 in the motor controller can be independent of other processing units or integrated with other processing units to become a comprehensive processing unit with more control functions.

[0065] The motor in the electric vehicle is usually a three-phase AC motor, which requires three-phase AC to drive. In order to provide the three-phase AC required by the motor, the motor drive circuit 1122 is, for example, an inverter circuit, which converts the DC power provided by the power battery into the three-phase AC required by the motor. The inverter circuit, for example, includes three switch bridge arms, each of which is used to receive the input voltage (high voltage DC) provided by the power battery, each of which includes an upper bridge arm switch tube and a lower bridge arm switch tube, and the bridge arm midpoints of the three switch bridge arms respectively provide three-phase power to the three-phase winding of the motor through a three-phase power line to drive the motor to rotate, and the three-phase power line is connected from the bridge arm midpoints of the three switch bridge arms to the three-phase winding of the motor. The three power lines can be marked as U phase, V phase and W phase respectively. The switch tube is preferably an IGBT switch tube, and the gate of each switch tube receives a control signal (such as a PWM signal) sent by the control processing unit 1121, so as to achieve conduction or disconnection.

[0066] In order to solve the problem that it is currently impossible to determine whether there is an insulation problem with the three-phase power line of the motor, the present application proposes to set a fault detection circuit 1123 in the motor controller 112, which can at least be used to determine whether there is an insulation problem with the three-phase power line of the motor.

[0067] Taking into account the need to judge the three-phase power lines of the motor, the fault detection circuit 1123 can adopt three identical detection sub-circuits, and the input ends of the three detection sub-circuits are used to be respectively connected to the three-phase power lines (i.e., the three-phase power lines of the motor) of the motor drive circuit 1122 of the power system that provide three-phase power to the motor, and the output ends of the three detection sub-circuits are used to be respectively connected to the control processing unit of the power system to determine whether there is an insulation fault in each phase power line.

[0068] Figure 2 A schematic diagram of an embodiment of a phase detection subcircuit of a fault detection circuit for a power system of an electric vehicle according to the present application is shown.

[0069] The fault detection circuit 1123 may include three Figure 2 The detection subcircuit shown in the figure, each detection subcircuit is connected to one of the three-phase power lines of the motor. As shown in the figure, the detection subcircuit includes an operational amplifier U1; a first resistor R_1 and a second resistor R_2 are connected in series between the input end (voltage is Vi) of the detection subcircuit and the same-direction input end (+) of the operational amplifier U, and a reference voltage V is connected between the first resistor R_1 and the second resistor R_2. ref ; The third resistor R_3 and the fourth resistor R_4 are connected in series between the output end of the detection sub-circuit and the reverse input end (-) of the operational amplifier, and are connected to the output end (voltage is Vo) of the operational amplifier through the fifth resistor R_5 between the third resistor R_3 and the fourth resistor R_4; the output end of the operational amplifier is connected to the control processing unit of the power system as the output end of the detection sub-circuit.

[0070] As an implementation method, in order to ensure the insulation of the three phases and ensure the voltage isolation of the strong electric part (including the motor drive circuit, which is provided by the power battery with a high voltage power supply) and the weak electric part circuit (including the control processing unit, which is provided by the weak electric battery with a low voltage power supply), the value of the first resistor and the third resistor can be greater than 100MΩ, of course, not limited to this specific value, as long as the strong electric part and the weak electric part are isolated. In addition, in order to ensure the resistance value of the first resistor and the third resistor, multiple series-connected resistors can be included respectively to accurately configure their resistance values.

[0071] As an implementation method, a first capacitor C_1 is connected to ground between the first resistor and the second resistor, and a second capacitor C_2 is connected to ground between the second resistor and the same-direction input terminal of the operational amplifier, so that the second resistor, the first capacitor and the second capacitor form a filter circuit for filtering out interference when the three-phase switch tube is turned on; based on similar considerations, optionally, a third capacitor C_3 is connected to ground between the third resistor and the fourth resistor, and a fourth capacitor C_4 is connected between the fourth resistor and the reverse input terminal of the operational amplifier to the third resistor and the fifth resistor, and the fourth resistor, the third capacitor and the fourth capacitor form a filter circuit to filter out interference from the switch tube.

[0072] As an implementation method, a sixth resistor R_6 is connected to the output end of the operational amplifier to limit the current, and the value may be 1-2KΩ.

[0073] As an implementation method, the reference voltage V ref It can be provided by converting the weak-current battery in the power system of the electric vehicle.

[0074] Preferably, the output terminal Vo of the operational amplifier of the fault detection circuit can be connected to the control processing unit in the motor controller of the power system to determine its output voltage. In order to avoid damage to the control processing unit, the reference voltage V ref The value does not exceed the withstand voltage of the pin of the control processing unit, for example, it is less than 3V or 5V (depending on the actual control processing unit such as MCU chip specification requirements, usually 3V or 5V), so as to ensure that the voltage of the port of the control processing unit such as MCU (i.e. the port to which the output of the operational amplifier of the fault detection circuit is connected, such as the analog sampling port of the MCU) will not be too high and exceed the withstand voltage of the chip pin, protecting the chip from damage. On the other hand, preferably, a lower voltage is not taken, because if the voltage is too low, the anti-interference ability will be weaker, and the low voltage will result in a small range of chip sampling, resulting in lower sampling accuracy, so the value of 2.5V is taken as an example here as a suitable value.

[0075] Figure 3 A schematic diagram of an embodiment of a reference voltage generating circuit of the present application is shown.

[0076] As shown in the figure, the reference voltage generation circuit is a follower built by the operational amplifier U2. The voltage 5V is obtained from the weak battery in the power system through a 5V chip, and then connected to the same-direction input terminal (+) of the operational amplifier U2 through the resistor R13 after voltage division by resistors R15 and R16. The reverse input terminal of the operational amplifier U2 is directly connected to its own output terminal, and the reference voltage V is generated after the output terminal is connected to the resistor R14 for current limiting. refAmong them, the resistor R13 and the same-direction input terminal of the operational amplifier U2 are grounded through the capacitor C6, and the output terminal of the resistor R14 is grounded through the capacitor C7 to filter out interference. In addition, for example, the resistor R15 can be set to R16, and the reference voltage V can be obtained through the follower built by the operational amplifier U2 (to ensure the stability of the voltage). ref =2.5V, the specific reference voltage required is V ref Can be configured as required.

[0077] Based on the fault detection circuit described above, the control processing unit can determine the insulation fault of the three-phase power line of the motor.

[0078] Figure 4 A schematic diagram of an embodiment of a process for determining a three-phase insulation fault in a motor power line of a power system of an electric vehicle according to the present application is shown.

[0079] Step S41, in response to the high voltage power-on and normal initialization, one of the three switch bridge arms is opened and then closed respectively, so as to respectively determine the three-phase voltages Vo_U, Vo_V, and Vo_W from the output ends of the three detection sub-circuits.

[0080] High voltage power-on means that the power battery starts to provide high voltage electricity. Normal initialization means that the electronic components are in a normal state after power-on but before they start working.

[0081] For example, if the upper tube in the U-phase switch bridge arm is turned on, Vo_U is recorded at this time, and then the upper tube of the U-phase is turned off; then the upper tube of the V-phase is turned on, Vo_V is recorded at this time, and then the upper tube of the V-phase is turned off; finally, the upper tube of the W-phase is turned on, Vo_W is recorded at this time, and then the upper tube of the W-phase is turned off. Of course, the lower tubes can also be turned on three times in sequence, or not in sequence, that is, as long as only one switch tube of one phase is turned on at the same time, it will be fine.

[0082] Step S42: Based on the insulation resistance value Rn of the positive terminal of the power battery busbar, the insulation resistance value Rp of the negative terminal of the power battery busbar, Vo_U, Vo_V, Vo_W, V ref , the resistance value of the fifth resistor, and the resistance values ​​of the first resistor and the second resistor or the third resistor and the fourth resistor, and the resistance values ​​Rx_u, Rx_v, and Rx_w of the three-phase power line to the shell are calculated.

[0083] Since the resistance value from the three-phase power line to the housing cannot be obtained directly, it needs to be indirectly calculated through the fault detection circuit provided in this application. The calculation process is based on basic circuit principles and calculates the required parameters based on known parameters.

[0084] Step S43: When at least one of Rx_u, Rx_v, and Rx_w is less than a predetermined threshold, it is determined that there is a three-phase insulation fault in the motor power line, and fault processing is performed. Fault processing includes shutdown protection, reporting faults, and the like.

[0085] As an implementation method, the control processing unit can receive Rn and Rp from the vehicle controller (VCU). Electric vehicles usually have an insulation tester that can measure the insulation resistance values ​​of the positive terminal Vdc+ of the power battery bus and the negative terminal Vdc- of the power battery bus to the protective ground PE of the shell (i.e., the ground GND of the weak battery / control power supply 12V / 24V), which are Rp and Rn respectively. After measuring this resistance value, it will be sent to the CAN (Controller Area Network) bus of the whole vehicle and received by the vehicle controller (VCU). After receiving it, the VCU can communicate with the control processing unit in the motor controller, such as the main drive controller (MCU), through the power CAN, and send these two values ​​to the control processing unit. Therefore, Rp and Rn can be regarded as known values.

[0086] As an implementation method, in response to high voltage power-on, when the switch tubes in the three switch bridge arms are all turned off, the initial three-phase voltages are determined from the output ends of the three detection sub-circuits. ref If the difference is within the preset range, it is judged that the initialization is normal.

[0087] That is to say, after the high voltage is powered on, in the initialization stage, all the switch tubes in the three-phase bridge arms U, V, and W are in the off state, and the initial three-phase voltage values ​​are measured from the output ends of the three detection sub-circuits respectively. When the three voltage values ​​are all within V ref If the value is close to , it is judged that the system initialization is normal.

[0088] As an implementation method, after determining that there is no abnormality in the insulation between the motor's three-phase wire and the housing, the motor drive control is performed. During the drive control process, it is also possible to determine whether there is a switch tube fault based on the fault detection circuit. This method can be used to determine whether the IGBT is turned on and off normally each time the motor drive circuit switches on and off. If there is an abnormal switch situation, it can be immediately determined and protection processing can be performed in time.

[0089] Figure 5 A schematic diagram of an embodiment of a switch tube fault judgment process for a power system of an electric vehicle according to the present application is shown.

[0090] Step S51, sending a control signal to the motor drive circuit to control the opening and closing of the switch tubes in the three switch bridge arms.

[0091] Step S52, according to the on and off conditions of the switch tube, based on the calculated Rx_u, Rx_v, and Rx_w, the theoretical values ​​of the three-phase voltages at the output ends of the three detection sub-circuits are calculated.

[0092] Step S53, determining actual values ​​of the three-phase voltages from the output terminals of the three detection sub-circuits respectively.

[0093] Step S54: When the difference between the theoretical value and the actual value of the corresponding phase voltage is greater than a predetermined threshold, it is determined to be a switch failure, and the failure is processed.

[0094] The following is a further example.

[0095] Figure 6 A schematic diagram of an embodiment of a power system for an electric vehicle according to the present application is shown.

[0096] The power system of electric vehicles mainly includes motors, inverter circuits (motor drive circuits, also called drivers) and main control MCU (control processing unit). The inverter circuit and MCU work in coordination to drive the motor to run, and the MCU sends a PWM signal. After passing through the driver board, six power switch tubes Q1-Q6 are opened in a certain order, and the motor is finally operated. As shown in the figure, in the present application, in order to be able to detect the insulation fault of the three-phase power line of the motor, the power system also includes a fault detection circuit, and the fault detection circuit includes a U-phase detection subcircuit, a V-phase detection subcircuit and a W-phase detection subcircuit. These three detection subcircuits are three identical detection circuits, which are respectively connected to the three-phase power line of the inverter circuit U, V, and W output terminals to the motor, and three voltage values ​​Vo_U, Vo_V, and Vo_W are respectively detected by the detection circuit and input to the main control MCU, and the three-phase power line is judged by the MCU whether it is abnormal, and the PWM wave controlled by the IGBT is turned off if there is an abnormality.

[0097] Figure 7 A schematic diagram of an embodiment of a phase detection subcircuit of a fault detection circuit for a power system of an electric vehicle according to the present application is shown.

[0098] The input end of the detection subcircuit is connected to the three-phase output end of the driver. The voltage is represented by Vi and is divided into two paths. One path is resistors R1, R3, R5, and R7 connected to the non-inverting input end (+) of the op amp U1, and a reference voltage V is added between R5 and R7. ref , and the other path is R2, R4, R6, and R8 connected to the inverting input terminal (-) of the operational amplifier U1, and at the same time connected between R6 and R8 to the output terminal of the operational amplifier U1 through a resistor R9.

[0099] For the convenience of subsequent calculations, R1+R3+R5=R2+R4+R6 can be set, and the sum of the resistance values ​​(R1+R3+R5 or R2+R4+R6) must be greater than 100MΩ (this value is an empirical value, not limited to this value) to ensure the insulation of the three phases and ensure that the strong current part and the weak current part circuit achieve voltage isolation through these two groups of resistors. R7, C3, and C5 form a filter circuit, and R8, C2, and C4 form a filter circuit to filter out interference when the three-phase IGBT is turned on. Resistor R10 is a current limiting resistor, generally around 1-2KΩ. Based on this, due to the "virtual short, virtual open" principle of the op amp, it can be obtained that V+=V-=V1=V ref , therefore, we can get formula (1):

[0100]

[0101] Since Vo can be directly obtained through sampling by the main control MCU, the voltage value of Vi can be directly calculated; the resistance value of R9 needs to be confirmed according to the bus voltage Vdc and the resistance values ​​of R2+R4+R6, for example: R1+R3+R5=100MΩ, then the resistance value of R9 is generally set at around 300K-1M, corresponding to a bus voltage of 800-250V.

[0102] According to Kirchhoff's current theorem at Vi, formula (2) can be obtained:

[0103]

[0104] Among them, V Q1 +V Q2 =Vdc,V Q1 、V Q2 are the voltage divisions of IGBT switch tubes Q1 and Q2 respectively; Rp and Rn are DC+ to the shell and DC- to the shell respectively. The resistance value can be detected in advance according to the vehicle (transmitted to the main control MCU through VCU), so the Rx value of the three-phase motor terminal U, V, and W to the shell can be calculated; under normal circumstances, if Q1 and Q2 are not turned on, V Q1 =V Q2 =1 / 2*Vdc, at this time V in =V ref , Rx value cannot be calculated, so it is necessary to turn on Q1 or Q2 separately. If Q1 is turned on and Q2 is turned off, V Q1 =0, V Q2 =Vdc, then the resistance of Rx can be calculated by formula (2). ref pass Figure 3 The voltage circuit is obtained, the reference voltage V ref =2.5V, the specific reference voltage required is V ref Can be configured as required.

[0105] Figure 8 A schematic diagram of an embodiment of a detection and protection process based on a fault detection circuit is shown.

[0106] based on Figure 7 The fault detection circuit can realize detection and protection through the following steps:

[0107] Step S71, after the high voltage is powered on, the initialization phase is entered. At this time, all the switch tubes of the three phases U, V, and W are in the off state. The main control MCU now obtains three initial detection voltage values ​​Vo_U', Vo_V', and Vo_W' through the three detection sub-circuits of the three phases, and determines that the three voltage values ​​at this time are all within V ref If the value is close to the specified value, the system is judged to be normal at this time, and the Rn and Rp values ​​sent by the VCU through CAN communication are recorded at this time.

[0108] Step S72, open one of the three phases V, V, and W in sequence and then close them; for example, open the upper tube of phase U and record Vo_U at this time, then close the upper tube of phase U, then open the upper tube of phase V and record Vo_V at this time, then close the upper tube of phase V, and finally open the upper tube of phase W and record Vo_W at this time, then close the upper tube of phase W; of course, it is also acceptable to open the lower tube three times in sequence.

[0109] Step S72, based on the Rn and Rp obtained in step S71 and the voltage value obtained in step S72, calculate the Rx value of each phase according to the previous formula (1) and formula (2). If Rx is less than 20M, an insulation fault of the phase is reported; otherwise, it is in normal state and the tube is opened normally.

[0110] Step S74, when it is judged to be in a normal state, the PWM is normally turned on when driving the motor, and the three-phase IGBT switch states are judged to be consistent by the voltages of Vo_U, Vo_V, and Vo_W according to the PWM on and off levels. For example, when PWM sends a U-phase lower tube on signal, the U-phase upper tube IGBT is not turned on, and the lower tube IGBT is turned on. Since Rx is a known quantity at this time, the corresponding Vo_U theoretical value can be obtained by equations (1) and (2). The actual value of Vo_U sampled by the MCU at this time is compared with its theoretical value. If the difference is too large, it is considered inconsistent.

[0111] Step S75: If the voltages of Vo_U, Vo_V, and Vo_W are inconsistent with the PWM level state, a switch failure is reported, such as an IGBT failure.

[0112] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0113] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0114] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A fault detection circuit for a power system of an electric vehicle, wherein: The fault detection circuit comprises three identical detection subcircuits, the input ends of the three detection subcircuits are respectively connected to the three-phase power lines of the motor drive circuit of the power system that provide three-phase power to the motor, and the output ends of the three detection subcircuits are respectively connected to the control processing unit of the power system; Each detection subcircuit includes: Operational amplifier; A first resistor and a second resistor are connected in series between the input end of the detection subcircuit and the same-direction input end of the operational amplifier, and a reference voltage V is connected between the first resistor and the second resistor. ref ; A third resistor and a fourth resistor, wherein the third resistor and the fourth resistor are connected in series between the input end of the detection subcircuit and the inverting input end of the operational amplifier, and connected to the output end of the operational amplifier through a fifth resistor between the third resistor and the fourth resistor; The output end of the operational amplifier is connected to the control processing unit of the power system as the output end of the detection subcircuit.

2. The fault detection circuit of claim 1, wherein: The values ​​of the first resistor and the third resistor are greater than 100 MΩ.

3. The fault detection circuit according to claim 1 or 2, wherein: The first resistor and the third resistor each include a plurality of resistors connected in series.

4. The fault detection circuit of claim 1, wherein: A first capacitor is connected to ground between the first resistor and the second resistor, and a second capacitor is connected to ground between the second resistor and the non-inverting input terminal of the operational amplifier; and / or, A third capacitor is connected to ground between the third resistor and the fourth resistor, and a fourth capacitor is connected between the fourth resistor and the inverting input terminal of the operational amplifier to between the third resistor and the fifth resistor; and / or, A sixth resistor is connected to the output terminal of the operational amplifier.

5. The fault detection circuit of claim 1, wherein: Reference voltage V ref Provided by the weak-current battery in the power system after conversion.

6. The fault detection circuit according to claim 1 or 5, wherein: Reference voltage V ref The value should be below 3V.

7. A motor controller for a power system of an electric vehicle, wherein: The motor controller comprises a motor drive circuit, a control processing unit and a fault detection circuit as claimed in any one of claims 1 to 6; The motor drive circuit comprises three switch bridge arms, both ends of each switch bridge arm are used to receive the input voltage provided by the power battery, each switch bridge arm comprises an upper bridge arm switch tube and a lower bridge arm switch tube, and the midpoints of the three switch bridge arms respectively provide three-phase power to the three-phase winding of the motor through the three-phase power line to drive the motor to rotate; The input ends of the three detection subcircuits of the fault detection circuit are respectively connected to the three-phase power line, and the output ends of the three detection subcircuits are respectively connected to the control processing unit; Based on the fault detection circuit, the control processing unit is used to: In response to the high voltage power-on and the initial state being normal, one of the switch tubes in the three switch bridge arms is respectively turned on and then turned off, so as to respectively determine the three-phase voltages Vo_U, Vo_V, and Vo_W from the output ends of the three detection sub-circuits; Based on the insulation resistance value Rn of the positive terminal of the power battery busbar, the insulation resistance value Rp of the negative terminal of the power battery busbar, Vo_U, Vo_V, Vo_W, V ref , a fifth resistor, and the first resistor and the second resistor or the third resistor and the fourth resistor, and calculate the resistance values ​​Rx_u, Rx_v, and Rx_w of the three-phase power line to the housing respectively; When at least one of Rx_u, Rx_v, and Rx_w is less than a predetermined threshold, it is determined to be a three-phase insulation fault of the motor power line, and fault processing is performed.

8. The motor controller according to claim 7, wherein: In response to the motor drive circuit being powered on and being in a normal initial state, the method comprises: In response to high voltage power-on, when the switch tubes in the three switch bridge arms are all turned off, the initial three-phase voltages are respectively determined from the output ends of the three detection sub-circuits; When the initial three-phase voltages are respectively ref If the difference is within the preset range, it is judged that the initialization is normal.

9. The motor controller of claim 7, wherein: The control processing unit obtains Rn and Rp from the vehicle controller VCU.

10. The motor controller of claim 7, wherein the method further comprises: Sending a control signal to the motor drive circuit to control the on and off of the switch tubes in the three switch bridge arms; According to the on and off conditions of the switch tube, based on the calculated Rx_u, Rx_v, and Rx_w, the theoretical values ​​of the three-phase voltages at the output ends of the operational amplifiers in the three detection sub-circuits are calculated; Determine the actual values ​​of the three-phase voltages from the output terminals of the operational amplifiers in the three detection subcircuits respectively; When the difference between the theoretical value and the actual value of the corresponding phase voltage is greater than a predetermined threshold, it is determined to be a switch tube failure and fault processing is performed.

11. A power system for an electric vehicle, comprising: A motor and a motor controller as claimed in claim 7.

12. An electric vehicle, comprising: A power battery and a power system as claimed in claim 11, wherein the power battery supplies power to the power system.

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