Battery heating control apparatus and method and electric vehicle

Abstract

The application provides a battery heating control device, method and electric vehicle, which comprises a motor controller and a motor, the motor controller and the motor are connected with a battery to form a heating loop, the motor controller comprises an inverter and a controller. The inverter comprises a three-phase bridge arm and a bus capacitor, the bus capacitor and the three-phase bridge arm are connected in parallel, the control ends of six switch modules of the three-phase bridge arm are connected with the controller respectively, and the midpoints of the three-phase bridge arm are electrically connected with three-phase stator windings of the motor respectively. The controller is used for detecting a rotor position angle of the motor. According to the detected rotor position angle, an angle range where the rotor position angle is located is confirmed. According to the angle range where the rotor position angle is located, the switching frequency or the duty cycle of the switch module in the inverter is adjusted. The application can avoid the problem of demagnetization of the motor magnetic steel in the battery heating process, can ensure the safety of the motor, and can also improve the heating efficiency of the battery.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a battery heating control device and method and an electric vehicle. Background Technology

[0002] Discharging batteries at low temperatures can easily lead to lithium plating, which can cause capacity degradation and battery safety hazards. Therefore, in low-temperature conditions, electric vehicles can only start operating when the battery is heated to a preset temperature.

[0003] Existing heating control methods involve fixing the duty cycle of the inverter's switching module in the battery heating system (e.g., D = 0.5). This allows the battery to alternate between rapid charging and discharging. Due to the battery's internal resistance, a large amount of heat is generated inside the battery, causing the temperature to rise rapidly. To maintain heating power, the losses in the motor's magnets will increase, potentially leading to demagnetization. This can cause significant damage to the motor, resulting in low heating safety. Summary of the Invention

[0004] In view of this, this application provides a battery heating control device and method and an electric vehicle, which can avoid the problem of demagnetization of the motor magnets during battery heating, ensure the safety of the motor, and improve the heating efficiency of the battery.

[0005] In a first aspect, embodiments of this application provide a battery heating control device, including a motor controller and a motor. The motor controller, the motor, and the battery are connected to form a heating circuit. The motor controller includes an inverter and a controller. The inverter includes a three-phase bridge arm and a bus capacitor. The bus capacitor and the three-phase bridge arm are connected in parallel. The control terminals of the six switching modules of the three-phase bridge arm are respectively connected to the controller. The midpoints of the three-phase bridge arm are respectively electrically connected to the three-phase stator windings of the motor. The controller is used to: detect the rotor position angle of the motor; confirm the angle range of the rotor position angle; and adjust the switching frequency or duty cycle of the switching modules in the inverter according to the angle range of the rotor position angle.

[0006] By employing the embodiments of this application, the angular range of the motor rotor position can be determined by detecting the rotor position. Therefore, the embodiments of this application can adjust the switching frequency or duty cycle of the switching module accordingly based on the angular range of the motor rotor position. This avoids the problem of demagnetization of the motor's magnets during battery heating, ensuring motor safety and improving battery heating efficiency.

[0007] As an optional implementation, the controller is further configured to: increase the switching frequency of the switching module when the motor loss corresponding to the rotor position angle of the motor reaches a first threshold; and decrease the switching frequency of the switching module when the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, wherein the second threshold is less than the first threshold. Based on this design, the switching frequency is increased at angles with low motor loss and decreased at angles with high motor loss, ensuring the thermal safety of the motor under heating conditions and improving the heating efficiency of battery internal resistance heating.

[0008] As an optional implementation, the controller is further configured to: reduce the duty cycle of the switching module when the motor loss corresponding to the rotor position angle of the motor reaches a first threshold; and increase the duty cycle of the switching module when the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, wherein the second threshold is less than the first threshold. Based on this design, the duty cycle is increased at angles with low motor loss and decreased at angles with high motor loss, ensuring the thermal safety of the motor under heating conditions and improving the heating efficiency of battery internal resistance heating.

[0009] As an optional implementation, the controller is further configured to: increase the switching frequency of the switching module and decrease the duty cycle of the switching module when the motor loss corresponding to the rotor position angle of the motor reaches a first threshold; and decrease the switching frequency of the switching module and increase the duty cycle of the switching module when the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, wherein the second threshold is less than the first threshold. Based on this design, the embodiments of this application can ensure the thermal safety of the motor under heating conditions and improve the heating efficiency of battery internal resistance heating.

[0010] As an optional implementation, the controller is further configured to: increase the switching frequency of the switching module when the motor torque corresponding to the rotor position angle of the motor reaches a third threshold; and decrease the switching frequency of the switching module when the motor torque corresponding to the rotor position angle of the motor reaches a fourth threshold, wherein the fourth threshold is less than the third threshold. Based on this design, the switching frequency is increased at angles with low motor torque and decreased at angles with high motor torque, ensuring the thermal safety of the motor under heating conditions and improving the heating efficiency of battery internal resistance heating.

[0011] As an optional implementation, the controller is further configured to: reduce the duty cycle of the switching module when the motor torque corresponding to the rotor position angle of the motor reaches a third threshold; and increase the duty cycle of the switching module when the motor torque corresponding to the rotor position angle of the motor reaches a fourth threshold, wherein the fourth threshold is less than the third threshold. Based on this design, the duty cycle is increased at angles with low motor torque and decreased at angles with high motor torque, ensuring the thermal safety of the motor under heating conditions and improving the heating efficiency of battery internal resistance heating.

[0012] As an optional implementation, the controller is further configured to: increase the switching frequency of the switching module and decrease the duty cycle of the switching module when the motor torque corresponding to the rotor position angle of the motor reaches a third threshold; and decrease the switching frequency of the switching module and increase the duty cycle of the switching module when the motor torque corresponding to the rotor position angle of the motor reaches a fourth threshold, wherein the fourth threshold is less than the third threshold. Based on this design, the embodiments of this application can ensure the thermal safety of the motor under heating conditions and improve the heating efficiency of battery internal resistance heating.

[0013] Secondly, embodiments of this application also provide a battery heating control method, applied in a battery heating control device. The battery heating control device includes a motor controller and a motor, the motor controller and the motor being connected to a battery to form a heating circuit. The motor controller includes an inverter and a controller; the inverter includes three-phase bridge arms and a bus capacitor, the bus capacitor and the three-phase bridge arms being connected in parallel, the control terminals of the six switching modules of the three-phase bridge arms being respectively connected to the controller, and the midpoints of the three-phase bridge arms being respectively electrically connected to the three-phase stator windings of the motor. The method includes: detecting the rotor position angle of the motor; confirming the angle range of the rotor position angle; and adjusting the switching frequency or duty cycle of the switching modules in the inverter according to the angle range of the rotor position angle.

[0014] By employing the embodiments of this application, the angular range of the motor rotor position can be determined by detecting the rotor position. Therefore, the embodiments of this application can adjust the switching frequency or duty cycle of the switching module accordingly based on the angular range of the motor rotor position. This avoids the problem of demagnetization of the motor's magnets during battery heating, ensuring motor safety and improving battery heating efficiency.

[0015] As an optional implementation, when the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the switching frequency of the switching module is increased; when the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the switching frequency of the switching module is decreased, wherein the second threshold is less than the first threshold. Based on this design, the switching frequency is increased at angles with low motor loss and decreased at angles with high motor loss, ensuring the thermal safety of the motor under heating conditions and improving the heating efficiency of battery internal resistance heating.

[0016] As an optional implementation, when the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the duty cycle of the switching module is reduced; when the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the duty cycle of the switching module is increased, wherein the second threshold is less than the first threshold. Based on this design, the duty cycle is increased at angles with low motor loss and decreased at angles with high motor loss, ensuring the thermal safety of the motor under heating conditions and improving the heating efficiency of battery internal resistance heating.

[0017] As an optional implementation, when the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the switching frequency of the switching module is increased and the duty cycle of the switching module is decreased; when the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the switching frequency of the switching module is decreased and the duty cycle of the switching module is increased, wherein the second threshold is less than the first threshold. Based on this design, the embodiments of this application can ensure the thermal safety of the motor under heating conditions and improve the heating efficiency of battery internal resistance heating.

[0018] As an optional implementation, when the motor torque corresponding to the rotor position angle of the motor reaches a third threshold, the switching frequency of the switching module is increased; when the motor torque corresponding to the rotor position angle of the motor reaches a fourth threshold, the switching frequency of the switching module is decreased, wherein the fourth threshold is less than the third threshold. Based on this design, the switching frequency is increased at angles with low motor torque and decreased at angles with high motor torque, ensuring the thermal safety of the motor under heating conditions and improving the heating efficiency of battery internal resistance heating.

[0019] As an optional implementation, when the motor torque corresponding to the rotor position angle of the motor reaches a third threshold, the duty cycle of the switching module is reduced; when the motor torque corresponding to the rotor position angle of the motor reaches a fourth threshold, the duty cycle of the switching module is increased, wherein the fourth threshold is less than the third threshold. Based on this design, the duty cycle is increased at angles with low motor torque and decreased at angles with high motor torque, ensuring the thermal safety of the motor under heating conditions and improving the heating efficiency of battery internal resistance heating.

[0020] As an optional implementation, when the motor torque corresponding to the rotor position angle of the motor reaches a third threshold, the switching frequency of the switching module is increased and the duty cycle of the switching module is decreased; when the motor torque corresponding to the rotor position angle of the motor reaches a fourth threshold, the switching frequency of the switching module is decreased and the duty cycle of the switching module is increased, wherein the fourth threshold is less than the third threshold. Based on this design, the embodiments of this application can ensure the thermal safety of the motor under heating conditions and improve the heating efficiency of battery internal resistance heating.

[0021] Thirdly, embodiments of this application also provide an electric vehicle, which includes the battery heating control device described above.

[0022] The embodiments of this application detect the rotor position angle of the motor and control the switching frequency and duty cycle of the switching module in the inverter to be different under different rotor position angles. Based on this design, the embodiments of this application can increase the switching frequency and the lithium plating threshold of the battery, thereby improving the reliability and efficiency of battery heating. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a battery heating control device provided according to an embodiment of this application.

[0024] Figure 2 This is another schematic diagram of a battery heating control device provided according to an embodiment of this application.

[0025] Figure 3 This is another schematic diagram of a battery heating control device provided according to an embodiment of this application.

[0026] Figure 4 This is a flowchart of a battery heating control method provided according to an embodiment of this application.

[0027] Figure 5 This is a graph showing the relationship between the rotor position angle of the motor and the motor losses.

[0028] Figure 6 This is a graph showing the relationship between the rotor position angle and the motor torque.

[0029] Figure 7 This is a schematic diagram of the ripple current of a motor at different rotor position angles according to an embodiment of this application.

[0030] Figure 8 This is another flowchart of a battery heating control method provided according to an embodiment of this application.

[0031] Figure 9 This is another flowchart of a battery heating control method provided according to an embodiment of this application.

[0032] Figure 10 This is a schematic diagram of an electric vehicle provided according to an embodiment of this application. Detailed Implementation

[0033] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] With the widespread use of new energy sources, batteries can be used as power sources in various fields. The performance of a battery is affected by the environment in which it is used as a power source. For example, the performance of a battery in low-temperature environments is significantly reduced compared to normal temperatures. Specifically, at zero temperature, the battery's discharge capacity decreases as the temperature drops. At -30℃, the battery's discharge capacity is essentially zero, rendering it unusable. To use the battery in low-temperature environments, it needs to be preheated before use. In some scenarios, the battery acts as the power source, and the motor inductor acts as the load for energy storage. The motor inductor can discharge, charging the battery, causing the battery's internal resistance to generate heat, thus heating the battery.

[0036] This application provides a battery heating control device, method, and electric vehicle. In specific scenarios where battery heating is required due to low battery temperature, the battery heating control device and method provided in this application can be used to control battery heating. It is understood that the battery can be used in electric vehicles to power the motor, serving as the power source for the electric vehicle. The battery can also power other electrical components in the electric vehicle, such as the in-vehicle air conditioner and in-vehicle media player.

[0037] The battery heating control device, method, and electric vehicle in this application embodiment can control the heating of the battery, avoid the problem of demagnetization of the motor magnets during battery heating, ensure motor safety, and improve battery heating efficiency. Using the battery heating control device and method provided in this application embodiment, the heating temperature distribution is uniform, the heating speed is fast, and the energy utilization rate is high.

[0038] Please see Figure 1 , Figure 1 The diagram shown is a schematic representation of a battery heating control device 100 according to an embodiment of this application. It can be understood that, in the embodiments of this application, the battery heating control device 100 can be applied to electric vehicles.

[0039] The battery heating control device 100 may include a battery 10, a motor controller 20, and a motor 30. The motor controller 20 is electrically connected between the battery 10 and the motor 30. In one possible application scenario, the high-voltage direct current provided by the battery 10 can be converted into alternating current by the motor controller 20 and supplied to the motor 30 to drive the electric vehicle.

[0040] In this embodiment, the motor controller 20 may include an inverter 22 and a controller 24.

[0041] The inverter 22 can be used to convert the DC power provided by the battery 10 into AC power and then transmit it to the three-phase motor. The input terminal of the inverter 22 can be used as the input terminal of the motor controller 20, and the output terminal of the inverter 22 can be used as the output terminal of the motor controller 20.

[0042] It is understood that when the electric vehicle is in motion, the battery 10 discharges, the input terminal of the inverter 22 receives the AC power transmitted by the battery 10, and the output terminal can transmit AC power to the motor 30. When the electric vehicle is AC charging, the output terminal of the inverter 22 receives the AC power input from the AC power source, and the input terminal of the inverter 22 outputs DC power to the battery 10.

[0043] The inverter 22 may include three-phase bridge arms connected in parallel. Each phase of the three-phase bridge arm has an upper bridge arm and a lower bridge arm, and each upper bridge arm is provided with a switching module, and each lower bridge arm is provided with a switching module, wherein the switching module has a diode.

[0044] In one alternative implementation, the controller 24 can detect the rotor position angle of the motor 30 and determine the angular range within which the rotor position angle of the motor 30 falls. Based on this design, the controller 24 can adjust the switching frequency or duty cycle of the switching module in the inverter 22 according to the rotor position angle of the motor 30.

[0045] like Figure 1 As shown, the three-phase bridge arms can be the U-phase bridge arm, V-phase bridge arm, and W-phase bridge arm. Specifically, the upper bridge arm switch module 201 of the U-phase bridge arm is the first switch module, and the lower bridge arm switch module 202 of the U-phase bridge arm is the second switch module. The upper bridge arm switch module 203 of the V-phase bridge arm is the third switch module, and the lower bridge arm switch module 204 of the V-phase bridge arm is the fourth switch module. The upper bridge arm switch module 205 of the W-phase bridge arm is the fifth switch module, and the lower bridge arm switch module 206 of the W-phase bridge arm is the sixth switch module.

[0046] It is understood that in some possible implementations, each switching module in the inverter 22 may include one or more power switching devices such as an Insulated Gate Bipolar Transistor (IGBT) chip, an IGBT module, and a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). The embodiments of this application do not limit the combination and connection methods of the IGBT and MOSFET devices in the switching modules. The material type of the aforementioned power switching devices is also not limited, and the power switching devices include diodes. Specifically, these can be parasitic diodes or intentionally designed diodes.

[0047] For example, the upper bridge arm switch module 201 may include a switch Q1 and a diode D1, and the lower bridge arm switch module 202 may include a switch Q2 and a diode D2. The first terminal of switch Q1 may be electrically connected to the controller 24, the second terminal of switch Q1 may be electrically connected to the positive terminal of the battery 10, and the third terminal of switch Q1 may be electrically connected to the second terminal of switch Q2. The first terminal of switch Q2 may be electrically connected to the controller 24, and the third terminal of switch Q2 may be electrically connected to the negative terminal of the battery 10. The cathode of diode D1 is electrically connected to the positive terminal of the battery 10, and the anode of diode D1 is electrically connected to the third terminal of switch Q1. The cathode of diode D2 is electrically connected to the second terminal of switch Q2, and the anode of diode D2 is electrically connected to the negative terminal of the battery 10. The first terminal of switch Q1 may serve as the control terminal of switch Q1, and the first terminal of switch Q2 may serve as the control terminal of switch Q2.

[0048] The upper bridge arm switch module 203 may include switch Q3 and diode D3, and the lower bridge arm switch module 204 may include switch Q4 and diode D4. The first terminal of switch Q3 may be electrically connected to the controller 24, the second terminal of switch Q3 may be electrically connected to the positive terminal of battery 10, and the third terminal of switch Q3 may be electrically connected to the second terminal of switch Q4. The first terminal of switch Q4 may be electrically connected to the controller 24, and the third terminal of switch Q4 may be electrically connected to the negative terminal of battery 10. The cathode of diode D3 is electrically connected to the positive terminal of battery 10, and the anode of diode D3 is electrically connected to the third terminal of switch Q3. The cathode of diode D4 is electrically connected to the second terminal of switch Q4, and the anode of diode D4 is electrically connected to the negative terminal of battery 10. The first terminal of switch Q3 may serve as the control terminal of switch Q3, and the first terminal of switch Q4 may serve as the control terminal of switch Q4.

[0049] The upper bridge arm switch module 205 may include switch Q5 and diode D5, and the lower bridge arm switch module 206 may include switch Q6 and diode D6. The first terminal of switch Q1 may be electrically connected to the controller 24, the second terminal of switch Q1 may be electrically connected to the positive terminal of battery 10, the third terminal of switch Q1 may be electrically connected to the second terminal of switch Q2, the first terminal of switch Q2 may be electrically connected to the controller 24, and the third terminal of switch Q2 may be electrically connected to the negative terminal of battery 10. The cathode of diode D1 is electrically connected to the positive terminal of battery 10, and the anode of diode D1 is electrically connected to the third terminal of switch Q1. The cathode of diode D2 is electrically connected to the second terminal of switch Q2, and the anode of diode D2 is electrically connected to the negative terminal of battery 10. The first terminal of switch Q5 may serve as the control terminal of switch Q5, and the first terminal of switch Q6 may serve as the control terminal of switch Q6.

[0050] In this embodiment, the motor 30 may include three-phase windings corresponding to the three-phase bridge arms respectively. One end of each of the three-phase windings is connected to the others, and the other end of each winding is connected to the connection point of the upper and lower bridge arms of their respective bridge arms. In one implementation, the three-phase windings may be stator inductors.

[0051] like Figure 1 As shown, there is a U-phase stator winding L1 corresponding to the U-phase bridge arm, a V-phase stator winding L2 corresponding to the V-phase bridge arm, and a W-phase stator winding L3 corresponding to the W-phase bridge arm. The first ends of the U-phase stator winding L1, the V-phase stator winding L2, and the W-phase stator winding L3 are connected. The second end of the U-phase stator winding L1 is connected to the connection point between the upper bridge arm switch module 201 and the lower bridge arm switch module 202; the second end of the V-phase stator winding L2 is connected to the connection point between the upper bridge arm switch module 203 and the lower bridge arm switch module 204; and the second end of the W-phase stator winding L3 is connected to the connection point between the upper bridge arm switch module 205 and the lower bridge arm switch module 206.

[0052] It is understood that in this embodiment, the battery heating control device 100 may further include a bus capacitor C1 connected in parallel with each phase arm of the inverter 22. The first terminal of the bus capacitor C1 may be electrically connected to the positive terminal of the battery 10, and the second terminal of the bus capacitor C1 may be electrically connected to the negative terminal of the battery 10. In one possible implementation, the bus capacitor C1 may be used to absorb the high pulsating voltage and current that may be generated when the switching module of the inverter 22 is disconnected, thereby keeping the voltage and current fluctuations in the battery heating control device within an allowable range and avoiding high voltage and current overshoot.

[0053] It is understandable that, in energy storage and freewheeling states, pulsed current can flow through the battery's internal resistance, causing the internal resistance to heat up, thereby achieving battery heating. Figure 2 The diagram shows the current flow of the battery heating control device in energy storage mode. The controller 24 can output a drive signal to the inverter 22 to control the upper arm switch module 201, lower arm switch module 204, and lower arm switch module 206 to conduct, and control the lower arm switch module 202, upper arm switch module 203, and upper arm switch module 205 to disconnect. When these are open, current flows from the positive terminal of the battery 10, through the upper arm switch module 201, into the U-phase stator winding L1, and then from the V-phase stator winding L2 and W-phase stator winding L3, through the lower arm switch module 204 and lower arm switch module 206 respectively, out of the motor controller 20, and finally into the negative terminal of the battery 10. This process can store energy in the U-phase stator winding L1, V-phase stator winding L2, and W-phase stator winding L3 of the three-phase motor. In this state, the current in the battery flows out from the positive terminal and into the negative terminal. The magnitude of the pulse current can be adjusted by regulating the conduction time of the upper bridge arm switch module 201, lower bridge arm switch module 204, and lower bridge arm switch module 206; the longer the conduction time, the larger the pulse current. The energy stored in the U-phase stator winding L1, V-phase stator winding L2, and W-phase stator winding L3 of the three-phase motor charges the battery through the freewheeling circuit.

[0054] Figure 3 The diagram shows the current flow of the battery heating control device in freewheeling mode. When the upper bridge arm switch module 201, lower bridge arm switch module 204, and lower bridge arm switch module 206 are turned on, and the lower bridge arm switch module 202, upper bridge arm switch module 203, and upper bridge arm switch module 205 are turned off, due to the characteristics of inductance, the current direction in the U-phase stator winding L1, V-phase stator winding L2, and W-phase stator winding L3 does not change immediately. The current flows out of the W-phase stator winding L3, then through the freewheeling diode of the upper bridge arm switch module 205, flows out of the motor controller 20, and then flows into the positive terminal of the battery 10. The current flows out of the V-phase stator winding L2, then through the freewheeling diode of the upper bridge arm switch module 203, flows out of the motor controller 20, and then flows into the positive terminal of the battery 10. The current flows out of the negative terminal of the battery 10, then through the freewheeling diode of the lower bridge arm switch module 202, and flows into the U-phase stator winding L1, thus forming a freewheeling circuit. In this state, the current in the battery flows in from the positive terminal and flows out from the negative terminal. The direction of the current flowing through the battery in this process is opposite to that in the energy storage state.

[0055] In one possible scenario, when the switching frequency in the inverter 22 remains fixed, the peak inductor current of the motor 30 will change under different rotor position angles with varying motor losses. A large peak inductor current will lead to excessive heat generation in the motor, potentially causing demagnetization of the motor's magnets. Conversely, a small peak inductor current will result in low battery heating efficiency.

[0056] It is understandable that in some possible scenarios, the motor 30 may have different motor losses at different rotor position angles.

[0057] In one optional implementation, the controller 24 can adjust the switching frequency of the switching module in the inverter 22 based on the motor losses corresponding to different rotor position angles of the motor 30. For example, if the motor loss corresponding to the rotor position angle of the motor 30 reaches a first threshold, the controller 24 increases the switching frequency of the switching module. If the motor loss corresponding to the rotor position angle of the motor 30 reaches a second threshold, the controller 24 decreases the switching frequency of the switching module, wherein the second threshold is less than the first threshold.

[0058] In one alternative implementation, the controller 24 can adjust the duty cycle of the switching module in the inverter 22 based on the motor losses corresponding to different rotor position angles of the motor 30. For example, if the motor loss corresponding to the rotor position angle of the motor 30 reaches a first threshold, the controller 24 reduces the duty cycle of the switching module. If the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the controller 24 increases the duty cycle of the switching module.

[0059] In another optional implementation, the controller 24 can adjust the switching frequency and duty cycle of the switching module in the inverter 22 based on the motor losses corresponding to different rotor position angles of the motor 30. For example, if the motor loss corresponding to the rotor position angle of the motor 30 reaches a first threshold, the controller 24 increases the switching frequency of the switching module and decreases the duty cycle of the switching module. If the motor loss corresponding to the rotor position angle of the motor 30 reaches a second threshold, the controller 24 decreases the switching frequency of the switching module and increases the duty cycle of the switching module.

[0060] It is understood that, among the above-mentioned multiple optional implementation methods, the second threshold is less than the first threshold.

[0061] In other possible scenarios, the motor 30 can correspond to different motor torques at different rotor position angles.

[0062] In one optional implementation, the controller 24 can adjust the switching frequency of the switching module in the inverter 22 based on the motor torque corresponding to different rotor position angles of the motor 30. For example, if the motor torque corresponding to the rotor position angle of the motor 30 reaches a third threshold, the controller 24 increases the switching frequency of the switching module. If the motor torque corresponding to the rotor position angle of the motor 30 reaches a fourth threshold, the controller 24 decreases the switching frequency of the switching module.

[0063] In another alternative implementation, the controller 24 can adjust the duty cycle of the switching module in the inverter 22 based on the motor torque corresponding to different rotor position angles of the motor 30. For example, if the motor torque corresponding to the rotor position angle of the motor 30 reaches a third threshold, the controller 24 reduces the duty cycle of the switching module. If the motor torque corresponding to the rotor position angle of the motor 30 reaches a fourth threshold, the controller 24 increases the duty cycle of the switching module.

[0064] In one optional implementation, the controller 24 can adjust the switching frequency and duty cycle of the switching module in the inverter 22 based on the motor torque corresponding to different rotor position angles of the motor 30. For example, if the motor torque corresponding to the rotor position angle of the motor 30 reaches a third threshold, the controller 24 increases the switching frequency of the switching module and decreases the duty cycle of the switching module. If the motor torque corresponding to the rotor position angle of the motor 30 reaches a fourth threshold, the controller 24 decreases the switching frequency of the switching module and increases the duty cycle of the switching module.

[0065] It is understood that, among the above-mentioned optional implementations, the fourth threshold is less than the third threshold. For details regarding the method by which the controller 24 controls the duty cycle or switching frequency of the switching module, please refer to the following... Figures 4 to 9 The relevant description in the document.

[0066] Please see Figure 4 , Figure 4 The diagram shown is a flowchart of a battery heating control method according to an embodiment of this application. The battery heating control method can be applied to the battery heating control device 100, and the method may include the following steps:

[0067] Step S41: Detect the rotor position angle of the motor.

[0068] by Figure 1 Taking the battery heating control device 100 shown as an example, the controller 24 can detect the rotor position angle of the motor 30 in real time. It can be understood that 0 degrees of rotor position angle can be defined as the angle at which the A-axis and D-axis coincide.

[0069] Step S42: Confirm the angular range of the rotor position angle of the motor.

[0070] In this embodiment, the controller 24 can be set with multiple angle ranges. For example, angle range 1 can be 30–70 degrees, angle range 2 can be 20–30 degrees and 70–80 degrees, angle range 3 can be 15–20 degrees and 80–85 degrees, angle range 4 can be 10–15 degrees and 85–90 degrees, and angle range 5 can be 0–10 degrees and 90–120 degrees.

[0071] Therefore, the controller 24 can determine the specific angular range of the rotor position of the motor 30 based on the detected rotor position angle of the motor 30.

[0072] For example, if the controller 24 detects that the rotor position angle of the motor 30 is 40 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 1. If the controller 24 detects that the rotor position angle of the motor 30 is 25 degrees or 75 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 2. If the controller 24 detects that the rotor position angle of the motor 30 is 82 degrees or 17 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 3. If the controller 24 detects that the rotor position angle of the motor 30 is 12 degrees or 87 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 4. If the controller 24 detects that the rotor position angle of the motor 30 is 95 degrees or 5 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 5.

[0073] Step S43: Adjust the switching frequency of the switching module in the inverter according to the angle range of the rotor position angle of the motor.

[0074] In one optional implementation, the rotor position angle of the motor 30 can correspond to different motor losses within different angle ranges. It is understood that, in another optional implementation, the rotor position angle of the motor 30 can also correspond to different motor torques within different angle ranges.

[0075] The controller 24 can adjust the switching frequency of the switching module in the inverter according to the motor loss or motor torque corresponding to the rotor position angle of the motor 30.

[0076] The following example illustrates how the switching frequency is adjusted based on the motor loss corresponding to the rotor position angle of the motor 30.

[0077] Please see Figure 5 , Figure 5 This is a graph showing the relationship between the rotor position angle of the motor 30 and the motor loss. When the rotor position angle of the motor 30 is within angle range 1, for example, angle range 1 is 30 to 70 degrees, the motor loss P of the motor 30 can be as follows: Figure 5 As shown in curve S1. When the rotor position angle of the motor 30 is within angle range 2, for example, angle range 2 is 20-30 degrees and 70-80 degrees, the motor loss P of the motor 30 can be as follows. Figure 5 Curves S2 and S3 are shown in the figure. When the rotor position angle of the motor 30 is within angle range 3, for example, angle range 3 is 15-20 degrees and 80-85 degrees, the motor loss P of the motor 30 can be as follows: Figure 5 Curves S4 and S5 are shown in the figure. When the rotor position angle of the motor 30 is within the angle range 4, for example, the angle range 4 is 10-15 degrees and 85-90 degrees, the motor loss P of the motor 30 can be as follows: Figure 5 Curves S6 and S7 are shown in the figure. When the rotor position angle of the motor 30 is within the angle range 5, for example, the angle range 5 is 0 to 10 degrees and 90 to 120 degrees, the motor loss P of the motor 30 can be as follows: Figure 5 Curves S8 and S9 are shown in the figure. In this embodiment, the motor loss P may include winding loss, magnet loss, silicon steel loss, and eddy current loss, etc.

[0078] like Figure 5 As shown, in this embodiment, when the motor loss P corresponding to the rotor position angle of the motor 30 reaches a first threshold P1, the controller 24 will correspondingly increase the switching frequency of the switching module in the inverter 22. When the motor loss P corresponding to the rotor position angle of the motor 30 reaches a second threshold P2, the controller 24 will correspondingly decrease the switching frequency of the switching module in the inverter 22. The second threshold P2 is less than the first threshold P1. It can be understood that the first threshold P1 may be the upper temperature limit of the motor corresponding to the winding loss, magnet loss, silicon steel loss, and eddy current loss.

[0079] It is understood that the controller 24 can determine the first threshold P1 based on the upper limit of the temperature at which the magnet of the motor 30 heats up.

[0080] For example, when the detected rotor position angle is 40 degrees, the rotor position angle is within angle range 1. The controller 24 will control the switching frequency of the switching module in the inverter 22 to f1 (e.g., 1 kHz) and can set the duty cycle D to 0.5. When the detected rotor position angle is 25 degrees or 75 degrees, the rotor position angle of the motor 30 is within angle range 2. The controller 24 will control the switching frequency of the switching module in the inverter 22 to f2 (e.g., 2 kHz) and set the duty cycle D to 0.5. When the detected rotor position angle of the motor 30 is 82 degrees or 17 degrees, the rotor position angle is within angle range 3. The controller 24 will control the switching frequency of the switching module in the inverter 22 to f3 (e.g., 3 kHz) and set the duty cycle D to 0.5. When the detected rotor position angle of the motor 30 is 12 degrees or 87 degrees, the rotor position angle is within angle range 4. The controller 24 will control the switching frequency of the switching module in the inverter 22 to f4 (e.g., 4kHz) and set the duty cycle D to 0.5. When the detected rotor position angle of the motor 30 is 95 degrees or 5 degrees, the rotor position angle is within angle range 5. The controller 24 will control the switching frequency of the switching module in the inverter 22 to f5 (e.g., 5kHz) and set the duty cycle D to 0.5.

[0081] It is understood that the switching frequency of the switching module in the inverter 22 can satisfy the following relationship: f1 <f2<f3<f4<f5。

[0082] Please see Figure 6 , Figure 6 This is a graph showing the relationship between the rotor position angle and the motor torque of the motor 30. When the rotor position angle of the motor 30 is within angle range 1, for example, angle range 1 is 30 to 90 degrees, the motor torque N of the motor 30 can be as follows: Figure 6 As shown in curve S11. When the rotor position angle of the motor 30 is within angle range 2, for example, angle range 2 is 10-30 degrees and 90-110 degrees, the motor torque N of the motor 30 can be as follows: Figure 6 Curves S12 and S13 are shown in the figure. When the rotor position angle of the motor 30 is within the angle range 3, for example, the angle range 3 is 0 to 10 degrees and 110 to 120 degrees, the motor torque N of the motor 30 can be as follows: Figure 6 Curves S14 and S15 are shown in the figure.

[0083] It is understood that, in another optional implementation, the controller 24 can adjust the switching frequency of the switching module in the inverter 22 based on the motor torque corresponding to the rotor position angle of the motor 30. For example, when the motor torque corresponding to the rotor position angle of the motor 30 reaches a third threshold N1, the controller 24 will increase the switching frequency of the switching module in the inverter 22. When the motor torque corresponding to the rotor position angle of the motor 30 reaches a fourth threshold N2, the controller 24 will decrease the switching frequency of the switching module in the inverter 22. The fourth threshold N2 is less than the third threshold N1.

[0084] In another alternative implementation, such as Figure 7 As shown, the peak current of the motor 30 can be close at different rotor position angles. Based on this design, the battery heating control method of this application embodiment can reduce the motor loss of the motor 30, ensure the thermal safety of the motor under heating conditions, and improve the heating efficiency of the battery internal resistance.

[0085] Please see Figure 8 , Figure 8 The diagram shown is a flowchart of a battery heating control method according to another embodiment of this application. The battery heating control method can be applied to the battery heating control device 100, and the method may include the following steps:

[0086] Step S81: Detect the rotor position angle of the motor.

[0087] by Figure 1 Taking the battery heating control device 100 shown as an example, the controller 24 can detect the rotor position angle of the motor 30 in real time.

[0088] Step S82: Confirm the angular range of the rotor position angle of the motor.

[0089] In this embodiment, the controller 24 can be set with multiple angle ranges. For example, angle range 1 can be 30–70 degrees, angle range 2 can be 20–30 degrees and 70–80 degrees, angle range 3 can be 15–20 degrees and 80–85 degrees, angle range 4 can be 10–15 degrees and 85–90 degrees, and angle range 5 can be 0–10 degrees and 90–120 degrees.

[0090] Therefore, the controller 24 can determine the specific angular range of the rotor position of the motor 30 based on the detected rotor position angle of the motor 30.

[0091] For example, if the controller 24 detects that the rotor position angle of the motor 30 is 40 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 1. If the controller 24 detects that the rotor position angle of the motor 30 is 25 degrees or 75 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 2. If the controller 24 detects that the rotor position angle of the motor 30 is 82 degrees or 17 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 3. If the controller 24 detects that the rotor position angle of the motor 30 is 12 degrees or 87 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 4. If the controller 24 detects that the rotor position angle of the motor 30 is 95 degrees or 5 degrees, then the controller 24 can confirm that the rotor position angle of the motor 30 is within angle range 5.

[0092] Step S83: Adjust the duty cycle of the switching module in the inverter according to the angle range of the rotor position angle.

[0093] It is understood that the controller 24 in this embodiment can adjust the duty cycle of the switching module in the inverter according to the motor loss or motor torque corresponding to the rotor position angle of the motor 30.

[0094] The following example illustrates how the duty cycle can be adjusted based on the motor loss corresponding to the rotor position angle of the motor 30.

[0095] Please refer to it again. Figure 5 When the rotor position angle of the motor 30 is within the angle range 1, the motor loss P of the motor 30 can be as follows: Figure 5 As shown in curve S1. When the rotor position angle of the motor 30 is within the angle range 2, the motor loss P of the motor 30 can be as follows. Figure 5 Curves S2 and S3 are shown in the figure. When the rotor position angle of the motor 30 is within the angle range 3, the motor loss P of the motor 30 can be as follows: Figure 5 Curves S4 and S5 are shown in the figure. When the rotor position angle of the motor 30 is within the angle range 4, the motor loss P of the motor 30 can be as follows: Figure 5 Curves S6 and S7 are shown in the figure. When the rotor position angle of the motor 30 is within the angle range 5, the motor loss P of the motor 30 can be as follows: Figure 5 Curves S8 and S9 are shown in the figure.

[0096] like Figure 5As shown, in this embodiment, when the motor loss corresponding to the rotor position angle of the motor 30 reaches the first threshold P1, the controller 24 will reduce the duty cycle of the switching modules in the inverter 22. For example, the controller 24 can reduce the duty cycle of switches Q1, Q4, and Q6. It can be understood that in this embodiment, the duty cycle can be such that at least one upper bridge arm and one lower bridge arm switch are simultaneously turned on.

[0097] When the motor loss corresponding to the rotor position angle of the motor 30 reaches the second threshold P2, the controller 24 will increase the duty cycle of the switching modules in the inverter 22. For example, the controller 24 can increase the duty cycle of switches Q1, Q4, and Q6.

[0098] For example, when the detected rotor position angle is 40 degrees, the rotor position angle is within angle range 1, and the controller 24 will control the duty cycle of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 to D1 (e.g., 0.5). When the detected rotor position angle is 25 degrees or 75 degrees, the rotor position angle of the motor 30 is within angle range 2, and the controller 24 will control the duty cycle of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 to D2 (e.g., 0.45). When the detected rotor position angle of the motor 30 is 82 degrees or 17 degrees, the rotor position angle is within angle range 3, and the controller 24 will control the duty cycle of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 to D3 (e.g., 0.4). When the detected rotor position angle of the motor 30 is 12 degrees or 87 degrees, the rotor position angle is within angle range 4, and the controller 24 controls the duty cycle of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 to D4 (e.g., 0.35). When the detected rotor position angle of the motor 30 is 95 degrees or 5 degrees, the rotor position angle is within angle range 5, and the controller 24 will control the duty cycle of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 to D5 (e.g., 0.3).

[0099] In this embodiment, the duty cycle of the switching module in the inverter 22 can satisfy the following relationship: D1≥D2≥D3≥D4≥D5.

[0100] The controller 24 can adjust the duty cycle of the switching module in the inverter 22 according to the rotor position angle of the motor 30 within different angle ranges.

[0101] Please refer to it again. Figure 6When the rotor position angle of the motor 30 is within the angle range 1, the motor torque N of the motor 30 can be as follows: Figure 6 As shown in curve S11. When the rotor position angle of the motor 30 is within the angle range 2, the motor torque N of the motor 30 can be as follows. Figure 6 Curves S12 and S13 are shown in the figure. When the rotor position angle of the motor 30 is within the angle range 3, the motor torque N of the motor 30 can be as follows: Figure 6 Curves S14 and S15 are shown in the figure.

[0102] It is understood that, in another optional implementation, the controller 24 can adjust the duty cycle of the switching module in the inverter 22 based on the motor torque corresponding to the rotor position angle of the motor 30. For example, when the motor torque corresponding to the rotor position angle of the motor 30 reaches a third threshold N1, the controller 24 will increase the duty cycle of the switching module in the inverter 22. When the motor torque corresponding to the rotor position angle of the motor 30 reaches a fourth threshold N2, the controller 24 will decrease the duty cycle of the switching module in the inverter 22. The fourth threshold N2 is less than the third threshold N1.

[0103] Please see Figure 9 , Figure 9 The diagram shown is a flowchart of a battery heating control method according to another embodiment of this application. The battery heating control method can be applied to the battery heating control device 100, and the method may include the following steps:

[0104] Step S91: Detect the rotor position angle of the motor 30.

[0105] by Figure 1 Taking the battery heating control device 100 shown as an example, the controller 24 can detect the rotor position angle of the motor 30 in real time.

[0106] Step S92: Confirm the angular range of the rotor position angle of the motor.

[0107] Step S93: Adjust the switching frequency and duty cycle of the switching module in the inverter according to the angle range of the rotor position angle.

[0108] The controller 24 can adjust the switching frequency and duty cycle of the switching module in the inverter according to the motor loss or motor torque corresponding to the rotor position angle of the motor 30.

[0109] Please refer to it again. Figure 5When the motor loss due to the rotor position angle of the motor 30 reaches a first threshold P1, the controller 24 will increase the switching frequency of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 and decrease the duty cycle of the switching modules. When the motor loss due to the rotor position angle of the motor 30 reaches a second threshold, the controller 24 will decrease the switching frequency of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 and increase the duty cycle of the switching modules. The second threshold P2 is less than the first threshold P1.

[0110] In another possible scenario, please refer again. Figure 6 When the motor torque at the rotor position angle of the motor 30 reaches the third threshold N1, the controller 24 will increase the switching frequency of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 and decrease the duty cycle of the switching modules. When the motor torque at the rotor position angle of the motor 30 reaches the fourth threshold N2, the controller 24 will decrease the switching frequency of the switching modules (e.g., switches Q1, Q4, and Q6) in the inverter 22 and increase the duty cycle of the switching modules.

[0111] It is understandable that during the battery heating process, a large peak-to-peak ripple value will lead to the risk of temperature rise in the motor's magnets. At different rotor position angles of the motor, due to different motor losses or motor torques of the motor 30, the peak-to-peak ripple value of the heating will be different. In this embodiment, the switching frequency or duty cycle can be adjusted according to the rotor position angle of the motor to ensure that the ripple current does not exceed the magnet's tolerance temperature, improve the heating power, and ensure that the motor's magnets will not demagnetize.

[0112] Please see Figure 10 The embodiments of this application also provide an electric vehicle 200, which may include the battery heating control device 100 described in the above embodiments.

[0113] By employing embodiments of this application, the switching frequency and duty cycle of the switching module in the inverter can be adjusted by detecting the rotor position angle of the motor and adjusting the switching frequency and duty cycle under different rotor position angles. Based on this design, embodiments of this application can increase the switching frequency and the lithium plating threshold of the battery, thereby improving the reliability and efficiency of battery heating.

[0114] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although the preferred embodiment has been disclosed above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A battery heating control device, characterized in that, The device includes a motor controller and a motor, the motor controller and the motor being connected to a battery to form a heating circuit, the motor controller including an inverter and a controller; The inverter includes a three-phase bridge arm and a bus capacitor. The bus capacitor and the three-phase bridge arm are connected in parallel. The control terminals of the six switching modules of the three-phase bridge arm are respectively connected to the controller. The midpoint of the three-phase bridge arm is electrically connected to the three-phase stator windings of the motor. The controller is used for: Detect the rotor position angle of the motor; Confirm the angular range within which the rotor position angle falls; Based on the angular range of the rotor position angle, the switching frequency or duty cycle of the switching module in the inverter is adjusted to control the ripple current of the motor at the rotor position angle.

2. The battery heating control device according to claim 1, characterized in that, The controller is used for: When the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the switching frequency of the switching module is increased. When the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the switching frequency of the switching module is reduced, wherein the second threshold is less than the first threshold.

3. The battery heating control device according to claim 1 or 2, characterized in that, The controller is also used for: When the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the duty cycle of the switching module is reduced. When the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the duty cycle of the switching module is increased, wherein the second threshold is less than the first threshold.

4. The battery heating control device according to claim 1, characterized in that, The controller is also used for: When the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the switching frequency of the switching module is increased and the duty cycle of the switching module is decreased. When the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the switching frequency of the switching module is reduced and the duty cycle of the switching module is increased, wherein the second threshold is less than the first threshold.

5. The battery heating control device according to claim 1, characterized in that, The controller is also used for: When the motor torque corresponding to the rotor position angle of the motor reaches the third threshold, the switching frequency of the switching module is increased. When the motor torque corresponding to the rotor position angle of the motor reaches a fourth threshold, the switching frequency of the switching module is reduced, wherein the fourth threshold is less than the third threshold.

6. The battery heating control device according to claim 1 or 5, characterized in that, The controller is also used for: When the motor torque corresponding to the rotor position angle of the motor reaches the third threshold, the duty cycle of the switching module is reduced. When the motor torque corresponding to the rotor position angle of the motor reaches the fourth threshold, the duty cycle of the switching module is increased, wherein the fourth threshold is less than the third threshold.

7. The battery heating control device according to claim 1, characterized in that, The controller is also used for: When the motor torque corresponding to the rotor position angle of the motor reaches the third threshold, the switching frequency of the switching module is increased and the duty cycle of the switching module is decreased. When the motor torque corresponding to the rotor position angle of the motor reaches the fourth threshold, the switching frequency of the switching module is reduced and the duty cycle of the switching module is increased, wherein the fourth threshold is less than the third threshold.

8. A battery heating control method, applied in a battery heating control device, the battery heating control device comprising a motor controller and a motor, the motor controller and the motor being connected to a battery to form a heating circuit, the motor controller comprising an inverter and a controller; the inverter comprising three-phase bridge arms and a bus capacitor, the bus capacitor and the three-phase bridge arms being connected in parallel, the control terminals of six switching modules of the three-phase bridge arms being respectively connected to the controller, and the midpoints of the three-phase bridge arms being respectively electrically connected to the three-phase stator windings of the motor, characterized in that... The method includes: Detect the rotor position angle of the motor; Confirm the angular range within which the rotor position angle falls; Based on the angular range of the rotor position angle, the switching frequency or duty cycle of the switching module in the inverter is adjusted to control the ripple current of the motor at the rotor position angle.

9. The battery heating control method according to claim 8, characterized in that, When the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the switching frequency of the switching module is increased. When the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the switching frequency of the switching module is reduced, wherein the second threshold is less than the first threshold.

10. The battery heating control method according to claim 8 or 9, characterized in that, When the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the duty cycle of the switching module is reduced. When the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the duty cycle of the switching module is increased, wherein the second threshold is less than the first threshold.

11. The battery heating control method according to claim 8, characterized in that, When the motor loss corresponding to the rotor position angle of the motor reaches a first threshold, the switching frequency of the switching module is increased and the duty cycle of the switching module is decreased. When the motor loss corresponding to the rotor position angle of the motor reaches a second threshold, the switching frequency of the switching module is reduced and the duty cycle of the switching module is increased, wherein the second threshold is less than the first threshold.

12. The battery heating control method according to claim 8, characterized in that, When the motor torque corresponding to the rotor position angle of the motor reaches the third threshold, the switching frequency of the switching module is increased. When the motor torque corresponding to the rotor position angle of the motor reaches a fourth threshold, the switching frequency of the switching module is reduced, wherein the fourth threshold is less than the third threshold.

13. The battery heating control method according to claim 8 or 12, characterized in that, When the motor torque corresponding to the rotor position angle of the motor reaches the third threshold, the duty cycle of the switching module is reduced. When the motor torque corresponding to the rotor position angle of the motor reaches the fourth threshold, the duty cycle of the switching module is increased, wherein the fourth threshold is less than the third threshold.

14. The battery heating control method according to claim 8, characterized in that, When the motor torque corresponding to the rotor position angle of the motor reaches the third threshold, the switching frequency of the switching module is increased and the duty cycle of the switching module is decreased. When the motor torque corresponding to the rotor position angle of the motor reaches the fourth threshold, the switching frequency of the switching module is reduced and the duty cycle of the switching module is increased, wherein the fourth threshold is less than the third threshold.

15. An electric vehicle, characterized in that, The electric vehicle includes a battery heating control device as described in any one of claims 1-7.

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