Calibration device of motor phase current correction coefficient, motor inverter and electric drive system

Abstract

The invention relates to a calibration device for determining a phase current correction coefficient of a motor. The calibration device comprises a current source; at least one sampling resistor, wherein each sampling resistor is connected in series between a corresponding bridge arm in the inverter bridge and the current source; at least one switch element, wherein each switch element is connected in series with a corresponding sampling resistor, a corresponding bridge arm and the current source to form a current detection loop; and the control unit is configured to selectively switch on the corresponding current detection loop by controlling the on-off of the at least one switch element in a calibration program and collect the actual current value flowing through the corresponding current detection loop, and the control unit is further configured to read the current value of each phase in the motor and determine the current value of each phase in the motor. And calculating a current correction coefficient of each phase winding of the motor based on the read current value and the actual current value. The invention also relates to a motor inverter comprising the calibration device and an electric drive system comprising the motor inverter.

Description

Technical Field

[0001] The present application relates to the field of motors, and more specifically, to a calibration device for determining a phase current correction coefficient of a motor, a motor inverter including the calibration device, and an electric drive system including the motor inverter. Background Art

[0002] In the process of motor drive control of the vehicle, the phase current detection of the motor is a key link, and its measurement results directly affect the overall driving performance of the vehicle. For example, for permanent magnet synchronous motors, its phase current detection mostly adopts direct measurement method, that is, the three-phase line current after the drive circuit is inverted is directly measured by current sensor. The specific measurement circuit can usually be divided into resistance sampling, current transformer sampling and sampling through Hall current sensor. The current detection accuracy of these measurement circuits has certain limitations.

[0003] In particular, for mass-produced motor products, the calculation parameters currently used to implement current measurement mostly use the same theoretical parameters, and it is impossible to perform separate parameter calibration and correction for different products. Due to the differences between different batches of motor products, applying the same calculation parameters to differentiated products will result in poor consistency in current measurement accuracy, which in turn leads to poor consistency in motor torque control accuracy, affecting the overall performance of the vehicle. Summary of the invention

[0004] In view of this, according to a first aspect of the present application, a calibration device for determining a phase current correction coefficient of a motor is provided, wherein the motor is driven by a motor inverter, the motor inverter comprises a motor control board and an inverter bridge composed of a plurality of bridge arms, the motor control board is used to control the on and off of each bridge arm in the inverter bridge, and the calibration device comprises:

[0005] Current source;

[0006] At least one sampling resistor, each sampling resistor is connected in series between a corresponding bridge arm in the inverter bridge and the current source;

[0007] At least one switch element, each switch element is connected in series with a corresponding one of the at least one sampling resistor, a corresponding one of the bridge arms of the inverter bridge, and the current source to form a current detection loop; and

[0008] a control unit, wherein the control unit is configured to selectively connect the corresponding current detection loop by controlling the on and off of the at least one switch element in the calibration procedure, and collect the actual current value flowing through the corresponding current detection loop,

[0009] Wherein, the control unit is further configured to read the phase current values inside the motor from the motor control board, and calculate the current correction coefficients of each phase winding of the motor based on the read current values and the actual current values collected from the current detection circuit.

[0010] Advantageously, the inverter bridge is a three-phase inverter bridge, and the calibration device includes three sampling resistors and three switching elements, and each sampling resistor and each switching element are respectively connected in series with a corresponding lower arm of the inverter bridge.

[0011] Advantageously, the control unit and the motor control board communicate via a CAN bus. Wherein, when entering the calibration program, the control unit sends corresponding control instructions to the motor control board via the CAN bus to make the inverter bridge enter the active short-circuit mode.

[0012] Advantageously, the motor control board is configured to turn off all the upper arms of the inverter bridge and turn on all the lower arms of the inverter bridge when receiving the control instructions.

[0013] Advantageously, in the calibration program, the control unit is further configured to:

[0014] Disconnect all the three switching elements, and read the phase current value I1' on the motor winding where the first sampling resistor is located from the motor control board;

[0015] Connect the current detection circuit where the first sampling resistor is located by means of the first switching element, collect the actual current value I2 flowing through the current detection circuit, and read the phase current value I2' on the motor winding where the first sampling resistor is located from the motor control board; and

[0016] Calculate the current correction coefficient Kx for this motor winding based on the following formula:

[0017] Kx = (I2' - I1') / (I2).

[0018] Advantageously, the control unit is further configured to send the calculated current correction coefficient Kx to the motor control board via the CAN bus. During the normal operation of the motor, the motor control board is configured to compensate the measurement result of the motor phase current by using the current correction coefficient Kx.

[0019] Advantageously, the control unit is integrated in the motor control board.

[0020] Advantageously, each arm of the inverter bridge is selected from the group including field effect transistors, insulated gate bipolar transistors, and bipolar junction transistors.

[0021] According to a second aspect of the present application, a motor inverter is also provided, the motor inverter comprising:

[0022] An inverter bridge, the inverter bridge being composed of a plurality of bridge arms connected to each phase winding of the motor;

[0023] The calibration device for determining the phase current correction factor of the motor as described above; and

[0024] A motor control board is configured to control the on and off of each bridge arm in the inverter bridge, and to compensate the measurement result of the motor phase current by using the current correction coefficient obtained by the calibration device.

[0025] According to a third aspect of the present application, an electric drive system for a vehicle is also provided, the electric drive system comprising:

[0026] Motor;

[0027] A power battery, the power battery is used to provide power for the operation of the motor; and

[0028] The motor inverter as described above is configured to control the operation of the motor.

[0029] According to the calibration device for determining the phase current correction coefficient of the motor of the present application, it is proposed to obtain two sets of different phase current values ​​for each motor product, and to deduce the correction coefficient unique to each motor product based on the mathematical relationship between the detected value and the actual value. The correction coefficient can be further sent and stored in the motor control board, so that in the subsequent normal drive control process of the motor, the current correction coefficient stored in each motor product can be used to compensate and correct the measurement result of the motor phase current, thereby reducing the problem of poor consistency of current and torque control accuracy caused by individual differences between various motor products. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] By incorporating the accompanying drawings and Figure 1 With reference to the specific implementation methods used to illustrate certain principles of the present application, other features and advantages of the method of the present application will become clear or be described in more detail.

[0031] Figure 1 A schematic diagram of a conventional vehicle electric drive system is shown.

[0032] Figure 2 A circuit diagram of a calibration device for determining a phase current correction factor of a motor according to an exemplary embodiment of the present application is shown. DETAILED DESCRIPTION

[0033] The calibration device for determining the phase current correction coefficient of the motor according to the present application will be described below with reference to the accompanying drawings and by way of example. In the following description, many specific details are set forth so that those skilled in the art can have a more comprehensive understanding of the present application. However, it is obvious to those skilled in the art that the implementation of the present application may not have some of these specific details. Instead, it may be considered to implement the present application with any combination of the following features and elements, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments and advantages are for illustrative purposes only and should not be regarded as elements or limitations of the claims.

[0034] Figure 1 FIG. 1 shows a schematic diagram of a conventional vehicle electric drive system. Figure 1 As shown in , the electric drive system is mainly composed of a motor M (which is shown as a three-phase motor), a motor inverter and a power battery.

[0035] Corresponding to the three-phase motor, the motor inverter may include a three-phase inverter bridge H, which is connected to the three-phase winding of the motor in a star connection. The inverter bridge H may be composed of six switch tubes VT1 to VT6, wherein the switch tubes VT1, VT3, and VT5 form an upper bridge arm, and the switch tubes VT2, VT4, and VT6 form a lower bridge arm. The gate control end of each switch tube in the inverter bridge H may be connected to the motor control circuit board CP, which controls the conduction of each switch tube by outputting a PWM duty cycle signal to the switch tube, thereby controlling the running speed and direction of the motor.

[0036] During the operation of the above motors, the detection of motor phase current is particularly important, and the detection accuracy of phase current directly affects the control accuracy of motor torque. For mass-produced motor products, the calculation parameters currently used to implement current measurement mostly use the same theoretical parameters. Due to the differences between different batches of motor products, applying the same calculation parameters to differentiated products will lead to poor consistency in current measurement accuracy, which in turn leads to poor consistency in motor torque control accuracy, affecting the overall performance of the vehicle.

[0037] In order to ensure the consistency between the phase current measurement results of different motor products, the present application proposes a calibration device for determining the phase current correction coefficient of the motor. Figure 2 A circuit diagram of an exemplary embodiment of the calibration device is shown.

[0038] exist Figure 2In the embodiment shown in , the motor M can be selected as a three-phase motor, especially a permanent magnet synchronous motor M (abbreviated as "PMSM") that can be applied to the BSG system of a hybrid vehicle. The motor can be driven by a motor inverter, which specifically includes a motor control board CP and an inverter bridge H composed of multiple bridge arms VT1, VT2, VT3, VT4, VT5, and VT6, wherein the switch tubes VT1, VT3, and VT5 form an upper bridge arm, and the switch tubes VT2, VT4, and VT6 form a lower bridge arm. The motor control board CP can be connected to the control end of each bridge arm to control the on and off of each bridge arm in the inverter bridge H.

[0039] Here, each bridge arm may be selected from the group consisting of a field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT) and a bipolar junction transistor (BJT). Figure 2 The internal structure of the calibration device and its connection relationship with the existing motor control board are described by taking an N-channel MOS tube as an example.

[0040] For a three-phase motor, the calibration device can generally be composed of a current source CS1, three sampling resistors R1-R3, three switch elements K1-K3 and a control unit 10. Each sampling resistor is connected in series to a corresponding bridge arm ( Figure 2 Each switch element is connected in series with a corresponding one of the at least one sampling resistor, a corresponding one of the bridge arms in the inverter bridge, and the current source CS1 to form a current detection loop.

[0041] In the calibration procedure, the control unit 10 can selectively connect the corresponding current detection loop by controlling the on and off of each switch element, and collect the actual current values ​​I1 and I2 flowing through the corresponding current detection loop. In addition, the control unit 10 and the motor control board CP can communicate through the CAN bus. For example, the control unit 10 can read the current values ​​I1' and I2' of each phase inside the motor from the motor control board CP via the CAN bus, and calculate the current correction coefficient Kx of each phase winding of the motor based on the read current value and the actual current value collected from the current detection loop.

[0042] It is worth noting that before entering the calibration procedure, the inverter bridge H must be put into active short circuit mode (ASC). To this end, when entering the calibration procedure, the control unit 10 can send corresponding control instructions to the motor control board CP via the CAN bus to put the inverter bridge H into active short circuit mode.

[0043] for Figure 2For example, upon receiving the control command, the motor control board CP turns off all the upper bridge arms VT1, VT3, and VT5 in the inverter bridge H and turns on all the lower bridge arms VT2, VT4, and VT6 in the inverter bridge H. At this time, the stator winding of the motor and the MOS tube of the lower bridge arm form a closed loop. Only in this ASC state can the calibration procedure of the current correction parameters be executed.

[0044] Specifically, in the calibration procedure, the control unit 10 may first disconnect all three switch elements K1 to K3, and read the phase current value I1' on the motor winding where each sampling resistor is located from the motor control board CP. For example, the phase current values ​​on the three-phase windings U, V, and W corresponding to R1, R2, and R3 read from the motor control board CP may be I1'_U, I1',_V, and I1'_W, respectively, and the phase current values ​​may be used as the zero drift corresponding to the corresponding motor winding, because the current values ​​I1_U, I1_V, and I1_W on R1, R2, and R3 actually collected by the ammeter at this time are all 0A.

[0045] Subsequently, one of the switch elements K1, K2, and K3 is turned on to start the corresponding current detection loop. For example, the current detection loop where the first sampling resistor R1 is located can be turned on by means of the switch element K1 disposed on the U-phase winding. The actual current value I2 in the current detection loop can be collected by means of an ammeter, and the phase current value I2' on the motor winding where the first sampling resistor R1 is located can be read from the motor control board CP.

[0046] Finally, the current correction factor Kx for the motor winding is calculated based on the following formula:

[0047] Kx=(I2′-I1′) / (I2).

[0048] Assuming that the switch elements K1, K2, and K3 are turned on separately, the actual current values ​​on the ammeter can be read as I2_U, I2_V, and I2_W, respectively, and the three-phase current detection signals inside the calibrated motor product can be read through the CAN bus as I2'_U, I2'_V, and I2'_W, respectively. Based on this, the correction coefficients Kx_U, Kx_V, and Kx_W of each phase winding can also be determined based on the above formula.

[0049] After determining the current correction coefficient Kx of each phase winding, the control unit 10 may send the current correction coefficient Kx to the motor control board CP via the CAN bus. During the normal operation of the motor, the motor control board CP may use the current correction coefficient Kx to compensate the measurement result of the motor phase current. As an optional example, the control unit 10 may be integrated in the motor control board CP or be a part of the motor control board CP.

[0050] An exemplary embodiment of the present application also proposes a motor inverter, which includes: an inverter bridge H, which is composed of multiple bridge arms VT1, VT2, VT3, VT4, VT5, and VT6 connected to each phase winding of the motor; a calibration device for determining the phase current correction coefficient of the motor described in the above embodiments of the present application; and a motor control board CP, which is configured to control the on and off of each bridge arm in the inverter bridge H, and use the current correction coefficient obtained by the calibration device to compensate for the measurement result of the motor phase current.

[0051] An exemplary embodiment of the present application also proposes an electric drive system for a vehicle, which includes: a motor; a power battery, the power battery is used to provide power for the operation of the motor; and the motor inverter as described above, which is configured to control the operation of the motor.

[0052] According to the calibration device for determining the phase current correction coefficient of the motor of the present application, it is proposed to obtain two sets of different phase current values ​​for each motor product, and to deduce the correction coefficient unique to each motor product based on the mathematical relationship between the detected value and the actual value. The correction coefficient can be further sent and stored in the motor control board, so that in the subsequent normal drive control process of the motor, the current correction coefficient stored in each motor product can be used to compensate and correct the measurement result of the motor phase current, thereby reducing the problem of poor consistency of current and torque control accuracy caused by individual differences between various motor products.

[0053] Those skilled in the art will appreciate that the steps of the method of the present application are not limited to being implemented in the order listed above. In addition, in the present application, the terms "comprising" and "including" indicate that in addition to the steps directly and clearly stated in the specification and claims, the technical solution of the present application does not exclude the situation of having other steps that are not directly or clearly stated.

[0054] Although the present application has been disclosed as above with preferred embodiments, the present application is not limited thereto. Any changes and modifications made by any person skilled in the art without departing from the spirit and scope of the present application should be included in the protection scope of the present application, and therefore the protection scope of the present application should be subject to the scope defined by the claims.

Claims

1. A calibration device for determining a phase current correction factor of a motor, It is characterized in that The motor is driven by a motor inverter, the motor inverter comprises a motor control board (CP) and an inverter bridge (H) composed of a plurality of bridge arms (VT1, VT2, VT3, VT4, VT5, VT6), the motor control board (CP) is used to control the on and off of each bridge arm in the inverter bridge (H), and the calibration device comprises: Current source (CS1); At least one sampling resistor (R1, R2, R3), each sampling resistor being connected in series between a corresponding bridge arm in the inverter bridge and the current source (CS1); at least one switch element (K1, K2, K3), each switch element being connected in series with a corresponding one of the at least one sampling resistor, a corresponding one of the bridge arms of the inverter bridge, and the current source (CS1) to form a current detection loop; and A control unit (10), the control unit being configured to selectively connect a corresponding current detection loop by controlling the on and off of the at least one switch element in a calibration procedure, and to collect an actual current value flowing through the corresponding current detection loop, The control unit is further configured to read the current value of each phase inside the motor from the motor control board (CP), and calculate the current correction coefficient of each phase winding of the motor based on the read current value and the actual current value collected from the current detection circuit.

2. The calibration device for determining the phase current correction coefficient of the motor according to claim 1, It is characterized in that The inverter bridge (H) is a three-phase inverter bridge, and the calibration device comprises three sampling resistors and three switching elements, each sampling resistor and each switching element are respectively connected in series with a corresponding lower bridge arm in the inverter bridge.

3. The calibration device for determining the phase current correction coefficient of the motor according to claim 2, It is characterized in that The control unit (10) and the motor control board (CP) communicate via a CAN bus, wherein when a calibration program is entered, the control unit (10) sends a corresponding control instruction to the motor control board (CP) via the CAN bus to cause the inverter bridge (H) to enter an active short-circuit mode.

4. The calibration device for determining the phase current correction coefficient of the motor according to claim 3, It is characterized in that The motor control board (CP) is configured to turn off all upper bridge arms (VT1, VT3, VT5) in the inverter bridge (H) and turn on all lower bridge arms (VT2, VT4, VT6) in the inverter bridge (H) when receiving the control instruction.

5. The calibration device for determining the phase current correction coefficient of the motor according to claim 4, It is characterized in that In the calibration procedure, the control unit (10) is further configured to: All the three switch elements are disconnected, and a phase current value I1' on the motor winding where the first sampling resistor (R1) is located is read from the motor control board (CP); By means of a first switch element (K1), a current detection loop in which the first sampling resistor (R1) is connected, an actual current value I2 flowing through the current detection loop is collected, and a phase current value I2' on the motor winding in which the first sampling resistor (R1) is located is read from the motor control board (CP); and The current correction factor Kx for the motor winding is calculated based on the following formula: Kx = (I2' - I1') / (I2).

6. The calibration device for determining the phase current correction coefficient of the motor according to claim 5, It is characterized in that The control unit (10) is further configured to send the calculated current correction coefficient Kx to the motor control board (CP) via the CAN bus. During normal operation of the motor, the motor control board (CP) is configured to compensate the measurement result of the motor phase current using the current correction coefficient Kx.

7. A calibration device for determining a phase current correction factor of a motor according to any one of claims 1 to 6, It is characterized in that The control unit (10) is integrated in the motor control board (CP).

8. The calibration device for determining the phase current correction coefficient of a motor according to any one of claims 1 to 6, It is characterized in that Each bridge arm in the inverter bridge (H) is selected from the group consisting of field effect transistors, insulated gate bipolar transistors and bipolar junction transistors.

9. A motor inverter, It is characterized in that The motor inverter includes: An inverter bridge (H), which is composed of a plurality of bridge arms (VT1, VT2, VT3, VT4, VT5, VT6) connected to each phase winding of the motor; A calibration device for determining a phase current correction factor of a motor according to any one of claims 1 to 8; and A motor control board (CP) is configured to control the on and off of each bridge arm in the inverter bridge (H) and compensate the measurement result of the motor phase current using the current correction coefficient obtained by the calibration device.

10. An electric drive system for a vehicle, It is characterized in that The electric drive system includes: Motor; A power battery, the power battery is used to provide power for the operation of the motor; and The motor inverter according to claim 9, configured to control the operation of the motor.

Images