Motor controller and motor control method for electric vehicles

Abstract

This invention discloses a motor controller and a motor control method for an electric vehicle. The motor control method is applied to a motor controller used to control a motor, and the motor controller is powered by a battery. The motor control method includes: when the main relay of the motor controller suddenly trips, in a first stage, the diode and the first current-limiting resistor of the first set of protection circuits of the motor controller inject the surge current back into the battery to suppress the surge current; and in a second stage, the control unit of the motor controller turns on the discharge switch of the second set of protection circuits of the motor controller, and the discharge switch and the second current-limiting resistor of the second set of protection circuits release the surge current to a reference voltage range.

Description

Technical Field

[0001] This invention relates to a motor controller and motor control method for electric vehicles. Background Technology

[0002] With rising environmental awareness, electric vehicles are receiving increasing attention. Under normal conditions, when the electric vehicle is traveling at high speed and the driver suddenly brakes, the back electromotive force energy of the motor can be recharged to the high-voltage battery through the internal current path. This is called brake recharge.

[0003] However, if the main relay has tripped and is uncontrollable, or if the driver turns off the power of the electric vehicle (key-off), the instantaneous surge current caused by the back electromotive force will damage the power components (such as power switches) and other devices on the DC bus (also known as the busbar) inside the electric vehicle.

[0004] Therefore, there is a need for a motor controller and motor control method for electric vehicles that can solve the problem of instantaneous surge current damage to power switches and other devices caused by the back electromotive force of the electric vehicle motor. Summary of the Invention

[0005] According to one aspect of this application, a motor controller for an electric vehicle is proposed for controlling a motor, the motor controller being powered by a battery. The motor controller includes: a power distribution unit coupled to the battery, and a control unit coupled to the power distribution unit, the control unit having a power holding function. The power distribution unit includes: a main relay, a first set of protection circuits, and a second set of protection circuits. A first terminal of the main relay is coupled to the positive terminal of the battery, and a second terminal of the main relay is coupled to the positive terminal of a DC bus. The first set of protection circuits is connected in parallel to the main relay and coupled to the battery, the first set of protection circuits including: a diode and a first current-limiting resistor, wherein the diode is connected in series with the first current-limiting resistor. The second set of protection circuits includes: a discharge switch and a second current-limiting resistor, the discharge switch being connected in series with the second current-limiting resistor, the second set of protection circuits being connected in parallel between the positive and negative terminals of the DC bus, and the second set of protection circuits being positioned between the second terminal of the main relay and the positive terminal of the DC bus. When the main relay trips suddenly, in the first stage, the diode and the first current-limiting resistor of the first protection circuit inject the surge current back into the battery to suppress the surge current. In the second stage, the control unit turns on the discharge switch, and the discharge switch and the second current-limiting resistor of the second protection circuit release the surge current to the reference voltage range.

[0006] The control unit receives electric vehicle status information, which includes: motor speed, voltage value of the main relay, and voltage value of the DC bus.

[0007] The control unit determines whether the back electromotive force has reached the triggering condition for causing the surge current based on the motor speed and the voltage value of the DC bus; and if the main relay has been turned on and the back electromotive force has reached the triggering condition for causing the surge current, the control unit turns on the discharge switch.

[0008] Specifically, when the control unit checks that the main relay is normal, it checks whether the electric vehicle's rotational speed is higher than a reference speed, whether the electric vehicle's power is off, and whether the main relay has tripped. When the electric vehicle's rotational speed is higher than the reference speed, the electric vehicle's power is off, and the main relay has tripped, in the first stage, the diode and the first current-limiting resistor of the first protection circuit suppress the surge current and reinject it into the battery. In the second stage, the control unit turns on the discharge switch to release the surge current through the discharge switch and the second current-limiting resistor of the second protection circuit. The control unit determines whether the DC bus voltage is less than a safe value. When the control unit determines that the DC bus voltage is less than the safe value, the control unit turns off the discharge switch of the second protection circuit.

[0009] According to another aspect of this case, a motor control method for an electric vehicle is proposed, applied to a motor controller for controlling a motor, the motor controller being powered by a battery. The motor control method includes: when the main relay of the motor controller suddenly trips, in a first stage, a diode and a first current-limiting resistor of a first set of protection circuits of the motor controller inject the surge current back into the battery to suppress the surge current; and in a second stage, a control unit of the motor controller activates a discharge switch of a second set of protection circuits of the motor controller, the discharge switch and the second current-limiting resistor of the second set of protection circuits releasing the surge current to a reference voltage range.

[0010] The control unit has a power holding function; the first terminal of the main relay is coupled to the positive terminal of the battery, and the second terminal of the main relay is coupled to the positive terminal of the DC bus; the first set of protection circuits is connected in parallel to the main relay and coupled to the battery; the diode is connected in series with the first current-limiting resistor; the discharge switch is connected in series with the second current-limiting resistor; the second set of protection circuits is connected in parallel between the positive terminal and the negative terminal of the DC bus; and the second set of protection circuits is located between the second terminal of the main relay and the positive terminal of the DC bus.

[0011] The control unit receives electric vehicle status information, which includes: motor speed, voltage value of the main relay, and voltage value of the DC bus.

[0012] The control unit determines whether the back electromotive force has reached the triggering condition for causing the surge current based on the motor speed and the voltage value of the DC bus; and if the main relay has been turned on and the back electromotive force has reached the triggering condition for causing the surge current, the control unit turns on the discharge switch.

[0013] Specifically, when the control unit checks that the main relay is normal, it checks whether the electric vehicle's rotational speed is higher than a reference speed, whether the electric vehicle's power is off, and whether the main relay has tripped. When the electric vehicle's rotational speed is higher than the reference speed, the electric vehicle's power is off, and the main relay has tripped, in the first stage, the diode and the first current-limiting resistor of the first protection circuit suppress the surge current and reinject it into the battery. In the second stage, the control unit turns on the discharge switch to release the surge current through the discharge switch and the second current-limiting resistor of the second protection circuit. The control unit determines whether the DC bus voltage is lower than a safe value. When the control unit determines that the DC bus voltage is lower than the safe value, the control unit turns off the discharge switch of the second protection circuit.

[0014] To provide a better understanding of the above and other aspects of the present invention, specific embodiments are described below in conjunction with the accompanying drawings: Attached Figure Description

[0015] Figure 1 A circuit diagram of a motor controller for an electric vehicle according to an embodiment of this invention is shown.

[0016] Figure 2 A schematic diagram illustrating the operation of a motor controller for an electric vehicle according to an embodiment of this invention is shown.

[0017] Figure 3 This invention illustrates a motor control method for an electric vehicle according to an embodiment of the present invention.

[0018] In the attached figures, the following labels are used:

[0019] 100: Motor Controller

[0020] 110: Power stage

[0021] 120: Power Distribution Unit

[0022] 130: Control Unit

[0023] 140: Voltage converter

[0024] 50: Motor

[0025] 150, 160: Battery

[0026] 145: DC bus

[0027] 121: Main Relay

[0028] 123, 125: Protection circuit

[0029] D: Flywheel diode

[0030] R1, R2: Current-limiting resistors

[0031] SW: Discharge switch

[0032] P1, P2: Current paths

[0033] 310-360: Steps Detailed Implementation

[0034] The technical terms used in this specification are based on conventional terms in this technical field. Where this specification provides explanations or definitions for certain terms, the interpretation of those terms shall be based on the explanations or definitions provided in this specification. Each of the embodiments disclosed herein has one or more technical features. Where feasible, those skilled in the art may selectively implement some or all of the technical features in any embodiment, or selectively combine some or all of the technical features in these embodiments.

[0035] Figure 1 A circuit diagram of a motor controller for an electric vehicle according to an embodiment of this invention is shown. Figure 2 A schematic diagram illustrating the operation of a motor controller for an electric vehicle according to an embodiment of this invention is provided. Figure 1 As shown, a motor controller 100 for an electric vehicle according to an embodiment of this invention includes: a power stage 110, a power distribution unit (PDU) 120, a control unit 130, and a voltage converter 140. The motor controller 100 can control a motor 50. The motor controller 100 is further coupled to a first battery 150 and a second battery 160 to be powered by the first battery 150 and the second battery 160.

[0036] Power stage 110 is coupled to motor 50 to provide power to motor 50. In one embodiment of this invention, power stage 110 is, for example, but not limited to, a three-phase six-arm power stage. Power stage 110 includes: switches S1-S6 and capacitor CAP. Switches S1 and S4 are connected in series between the positive and negative terminals of DC bus 145. Switches S2 and S5 are connected in series between the positive and negative terminals of DC bus 145. Switches S3 and S6 are connected in series between the positive and negative terminals of DC bus 145. Switches S1-S6 are controlled by control unit 130. Capacitor CAP spans between the positive and negative terminals of DC bus 145.

[0037] The power distribution unit 120 includes: a main relay 121, a first set of protection circuits 123 and a second set of protection circuits 125.

[0038] A first terminal (negative terminal) of the main relay 121 is coupled to a positive terminal of the first battery 150, and a second terminal (positive terminal) of the main relay 121 is coupled to the positive terminal of the DC bus 145.

[0039] The first set of protection circuits 123 is connected in parallel with the main relay 121. The first set of protection circuits 123 includes a flywheel diode D and a first current-limiting resistor R1, wherein the flywheel diode D is connected in series with the first current-limiting resistor R1. This first set of protection circuits 123 is used to suppress surge current to prevent damage to other components. This first set of protection circuits 123 can inject surge current into the first battery 150 to suppress surge current.

[0040] The second protection circuit 125 includes a discharge switch SW and a second current-limiting resistor R2, with the discharge switch SW connected in series with the second current-limiting resistor R2. The second protection circuit 125 is connected in parallel between the positive and negative terminals of the DC bus 145. The second protection circuit 125 is positioned between the positive terminal of the main relay and the positive terminal of the DC bus 145, and can quickly suppress surge current and release surge voltage to a low voltage range.

[0041] In one embodiment of this case, when the main relay 121 suddenly trips, in the first stage, the flywheel diode D and the first current-limiting resistor R1 of the first protection circuit 123 inject the surge current back to the first battery 150 to achieve surge current suppression and achieve the effect of immediate current suppression. The surge current path in the first stage is as follows: Figure 2 The current path P1 is shown. Next, in the second stage, the surge current is released to the ground terminal by the discharge switch SW and the second current-limiting resistor R2 of the second set of protection circuits 125, so as to quickly release the surge current to an allowable low voltage range. The surge current path in the second stage is as follows: Figure 2 The current path P2 is shown.

[0042] Control unit 130 is coupled to power stage 110 and power distribution unit 120. Control unit 130 has a power hold function. That is, when the power supply to the electric vehicle is suddenly cut off, the power supply to control unit 130 will not be cut off immediately, and it can still temporarily maintain power for control operation.

[0043] In one embodiment of this invention, the control unit 130 may be, for example but not limited to, a vehicle control unit (VCU). The control unit 130 includes an electronic control unit (not shown) and control wiring (not shown). The electronic control unit can receive electric vehicle status information. The electric vehicle status information includes, for example but not limited to, motor speed, main relay voltage, and DC bus voltage. The electronic control unit can control the opening or closing of the discharge switch SW. The control unit 130 may be implemented by hardware, software, or firmware, all of which are within the spirit and scope of this invention.

[0044] A voltage converter 140 is coupled to a second battery 160 to convert the battery voltage of the second battery 160 and provide it to a DC bus 145. In one embodiment of this invention, the voltage converter 140 is, for example, but not limited to, a DC-DC voltage converter.

[0045] The first battery 150 is, for example but not limited to, a high-voltage battery. The first battery 150 is coupled to the main relay 121.

[0046] The second battery 160 is, for example but not limited to, a 12V battery. The second battery 160 is coupled to the voltage converter 140.

[0047] The motor control method of an electric vehicle according to one embodiment of this invention, or the motor back electromotive force energy recovery control method, can be used to control the motor controller 100. The motor control method of the electric vehicle is stored or installed in the control unit 130 in the form of software, firmware or circuit, and is read or started by the control unit 130 to execute the following steps: (1) The control unit 130 determines whether the back electromotive force has reached the triggering condition for causing a surge current based on the motor speed and the voltage value on the DC bus 145; (2) If the main relay 121 has been turned on and the back electromotive force has reached the triggering condition for causing a surge current, the control unit 130 turns on the discharge switch SW to achieve the effect of suppressing the current.

[0048] Figure 3 This invention illustrates a motor control method for an electric vehicle according to an embodiment of the present invention. In step 310, the control unit 130 checks whether the main relay 121 is functioning correctly. When the main relay 121 is functioning correctly, the process continues to step 320. When the main relay 121 is not functioning correctly, the process repeats step 310.

[0049] In step 320, control unit 130 checks whether the electric vehicle's rotational speed is higher than a reference speed (e.g., but not limited to, 5000 rpm), and control unit 130 checks whether the electric vehicle's power is off (key-off), and control unit 130 checks whether the main relay 121 has tripped. If all three checks in step 320 are true, the process continues to step 330. If at least one of the three checks in step 320 is false, the process repeats step 320.

[0050] In step 330, during the first stage, the surge current is suppressed by the flywheel diode D and the first current limiting resistor R1 of the first protection circuit 123 (the surge current is injected into the first battery 150), achieving the effect of immediate current suppression.

[0051] In step 340, the control unit 130 turns on the discharge switch SW of the second protection circuit 125. That is, in step 340, during the second stage, the surge current is released to the ground terminal by the discharge switch SW of the second protection circuit 125 and the second current limiting resistor R2, so as to quickly release the surge current to an allowable low voltage range.

[0052] In step 350, the control unit 130 determines whether the voltage on the DC bus is less than a safe value (e.g., but not limited to, 80V+10%).

[0053] If step 350 is true, the process continues to step 360. If step 350 is false, the process repeats step 350.

[0054] In step 360, the control unit 130 turns off the discharge switch SW of the second protection circuit 125.

[0055] As described above, in one embodiment of this case, protection is implemented from the perspective of the entire vehicle system by utilizing two sets of protection circuits (123 and 125) to achieve the effects of injecting back electromotive force energy back to the high-voltage battery 150 and suppressing surge current. In the first stage when the main relay 121 suddenly trips, the surge current is suppressed by the flywheel diode D of the first protection circuit 123 and the first current-limiting resistor R1, achieving the effect of immediate current suppression. Then, in the second stage, the surge current is rapidly released to an allowable low voltage range (e.g., but not limited to, 80V + 10%) by the discharge switch SW and the second current-limiting resistor R2 of the second set of protection circuits 125.

[0056] Experimental simulations show that in existing technologies, when a surge occurs and the main relay trips, the voltage on the DC bus can reach as high as 120V, and it takes a considerable amount of time to clear the surge. Conversely, in one embodiment of this invention, even with the main relay tripping, the voltage on the DC bus is limited to approximately 82V, and the surge can be reinjected into the high-voltage battery. Therefore, this embodiment not only suppresses surge voltage but also effectively reinjects energy into the high-voltage battery, achieving a high energy reuse rate.

[0057] Therefore, in one embodiment of this case, the vehicle system adopts two sets of protection circuits and control technology as a protection strategy to achieve the effect of recovering back EMF energy to the high-voltage battery (150) and suppressing surge current, so as to solve the problem of damage to power switches and other controllers caused by back EMF surge current.

[0058] In summary, although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0059] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A motor controller for an electric vehicle, characterized by, A motor controller for controlling a motor, the motor controller being powered by a battery, the motor controller comprising: A power distribution unit, coupled to the battery; and A control unit, coupled to the power distribution unit, has a power holding function. in, The power distribution unit includes: a main relay, a first set of protection circuits, and a second set of protection circuits; The first terminal of the main relay is coupled to the positive terminal of the battery, and the second terminal of the main relay is coupled to the positive terminal of the DC bus. The first set of protection circuits is connected in parallel to the main relay and coupled to the battery. The first set of protection circuits includes a diode and a first current-limiting resistor, wherein the diode is connected in series with the first current-limiting resistor. The second set of protection circuits includes: a discharge switch and a second current-limiting resistor, the discharge switch being connected in series with the second current-limiting resistor; the second set of protection circuits being connected in parallel between the positive and negative terminals of the DC bus; and the second set of protection circuits being positioned between the second terminal of the main relay and the positive terminal of the DC bus. When the main relay trips suddenly, in the first stage, the diode and the first current-limiting resistor of the first set of protection circuits inject the surge current back into the battery to suppress the surge current. In the second stage, the control unit turns on the discharge switch, and the discharge switch and the second current-limiting resistor of the second set of protection circuits release the surge current to the reference voltage range.

2. The motor controller according to claim 1, characterized in that, The control unit receives electric vehicle status information, which includes: motor speed, voltage value of the main relay, and voltage value of the DC bus.

3. The motor controller according to claim 1, characterized in that, The control unit determines whether the back electromotive force reaches the triggering condition that causes the surge current based on the motor speed and the voltage value of the DC bus. as well as If the main relay is already turned on and the back electromotive force has reached the triggering condition that causes the surge current, the control unit turns on the discharge switch.

4. The motor controller according to claim 1, characterized in that, When the control unit checks that the main relay is normal, the control unit checks whether the speed of the electric vehicle is higher than the reference speed, whether the power supply of the electric vehicle is turned off, and whether the main relay has tripped. When the rotational speed of the electric vehicle is higher than the reference rotational speed, and the power supply of the electric vehicle is off, and the main relay is tripped, during the first stage, the surge current is suppressed and reinjected into the battery by the diode and the first current-limiting resistor of the first set of protection circuits. During the second stage, the control unit turns on the discharge switch so that the surge current is released by the discharge switch of the second set of protection circuits and the second current limiting resistor. The control unit determines whether the DC bus voltage is less than a safe value; as well as When the control unit determines that the DC bus voltage is less than the safe value, the control unit closes the discharge switch of the second set of protection circuits.

5. A motor control method for an electric vehicle, characterized in that, This method is applied to a motor controller that controls a motor. The motor controller is battery-powered, and the motor control method is stored or installed in the motor's control unit, and is read or executed by the control unit after activation: When the main relay of the motor controller suddenly trips, in the first stage, the diodes and the first current-limiting resistor of the first set of protection circuits of the motor controller will inject the surge current back into the battery to suppress the surge current. as well as During the second phase, the control unit activates the discharge switch of the second set of protection circuits of the motor controller, and the discharge switch and the second current-limiting resistor of the second set of protection circuits release the surge current to the reference voltage range.

6. The motor control method according to claim 5, characterized in that, This control unit has a power holding function; The first terminal of the main relay is coupled to the positive terminal of the battery, and the second terminal of the main relay is coupled to the positive terminal of the DC bus. The first set of protection circuits is connected in parallel to the main relay, the first set of protection circuits is coupled to the battery, and the diode is connected in series with the first current-limiting resistor; and The discharge switch is connected in series with the second current-limiting resistor, the second set of protection circuits is connected in parallel between the positive terminal and the negative terminal of the DC bus, and the second set of protection circuits is placed between the second terminal of the main relay and the positive terminal of the DC bus.

7. The motor control method according to claim 5, characterized in that, The control unit receives electric vehicle status information, which includes: motor speed, voltage value of the main relay, and voltage value of the DC bus.

8. The motor control method according to claim 5, characterized in that, The control unit determines whether the back electromotive force reaches the triggering condition that causes the surge current based on the motor speed and the voltage value of the DC bus. as well as If the main relay is already turned on and the back electromotive force has reached the triggering condition that causes the surge current, the control unit turns on the discharge switch.

9. The motor control method according to claim 5, characterized in that, When the control unit checks that the main relay is normal, the control unit checks whether the speed of the electric vehicle is higher than the reference speed, whether the power supply of the electric vehicle is turned off, and whether the main relay has tripped. When the rotational speed of the electric vehicle is higher than the reference rotational speed, and the power supply of the electric vehicle is off, and the main relay is tripped, during the first stage, the surge current is suppressed and reinjected into the battery by the diode and the first current-limiting resistor of the first set of protection circuits. During the second stage, the control unit turns on the discharge switch so that the surge current is released by the discharge switch of the second set of protection circuits and the second current limiting resistor. The control unit determines whether the DC bus voltage is lower than a safe value; as well as When the control unit determines that the DC bus voltage is less than the safe value, the control unit closes the discharge switch of the second set of protection circuits.

Images