Battery heating method, system, and vehicle

Abstract

The present disclosure relates to a battery heating method, system and vehicle, which comprises the following steps: when it is determined to start battery heating, controlling the specified switch to be closed, and obtaining the lower limit value and upper limit value of the switching frequency of the switch tube in each phase bridge arm; determining the target switching frequency of the switch tube in each phase bridge arm at the current time according to the lower limit value and upper limit value of the switching frequency, wherein the target switching frequency of each switch tube at the current time is different from the first switching frequency at the previous sampling time and the second switching frequency at the next sampling time; controlling the switch tube in the bridge arm to be turned on or off according to the target switching frequency of the switch tube in each phase bridge arm at the current time, so that the first battery pack and the second battery pack are alternately charged and discharged to heat the power battery, which can effectively reduce the superposition of noise and magnetic field energy at the same frequency.

Description

Technical Field

[0001] This disclosure relates to the field of battery heating technology, specifically to a battery heating method, system, and vehicle. Background Technology

[0002] Currently, commonly used power battery heating methods include external heating and internal heating. External heating uses a PTC (Positive Temperature Coefficient) heater or a heating wire heater to heat the coolant in the battery cooling circuit at low temperatures, thereby heating the battery cells to a predetermined temperature. Internal heating uses a high-frequency alternating current to pass through the battery, thereby generating heat inside the battery. Compared with external heating, internal heating is faster and more uniform, and it does not require external heating hardware, simplifying the topology and reducing costs.

[0003] However, current internal heating methods utilize components in the motor system, such as the motor's inductors, windings, and the motor controller's bridge arms. These components vibrate under the electromagnetic excitation of large-amplitude, high-frequency alternating currents, which radiates high-frequency sound through thin-walled components such as the motor housing and the electronic control cover. Since the human ear is sensitive to high-frequency noise, this severely affects the driving experience of passengers inside and outside the vehicle during the battery heating process. Summary of the Invention

[0004] The purpose of this disclosure is to provide a battery heating method, system, and vehicle.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a battery heating method applied to a designated controller in a battery heating system. The battery heating system includes a power battery, a motor controller, a motor, a designated switch, and the designated controller. The power battery is formed by connecting a first battery pack and a second battery pack in series. The motor controller includes a multi-phase bridge arm, and the motor includes multi-phase windings. The midpoint of each phase bridge arm is connected to the first end of a phase winding. The second ends of each phase winding in the multi-phase windings are connected together and then connected to the first end of the designated switch. The second end of the designated switch is connected between the first battery pack and the second battery pack. The first busbar of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second busbar of the multi-phase bridge arm is connected to the negative terminal of the second battery pack. The method includes:

[0006] When it is determined that battery heating will be started, the designated switch is controlled to close, and the lower limit and upper limit of the switching frequency of the switching transistor in each phase arm are obtained.

[0007] The target switching frequency of the switching transistor in each phase arm at the current moment is determined based on the lower limit value of the switching frequency and the upper limit value of the switching frequency, wherein the target switching frequency of each switching transistor at the current moment is different from the first switching frequency of the switching transistor at the previous sampling moment and the second switching frequency at the next sampling moment.

[0008] The switching transistors in each phase arm are controlled to be turned on or off according to the target switching frequency of the transistors in each phase arm at the current moment, so that the first battery pack and the second battery pack are alternately charged and discharged to heat the power battery.

[0009] Optionally, determining the target switching frequency of the switching transistor in each phase arm at the current moment based on the lower limit of the switching frequency and the upper limit of the switching frequency includes:

[0010] Within the switching frequency adjustment range corresponding to the lower limit and the upper limit of the switching frequency, the target switching frequency is determined in an incremental and / or decremental manner.

[0011] Optionally, determining the target switching frequency within the switching frequency adjustment range corresponding to the lower and upper limits of the switching frequency, in an incremental and / or decremental manner, includes:

[0012] Determine the current switching frequency adjustment cycle;

[0013] Within the specified switching frequency adjustment period, the target switching frequency is first determined by increasing the lower limit of the switching frequency as the starting frequency and increasing by the first step value; then, the target switching frequency is determined by decreasing the upper limit of the switching frequency as the starting frequency and decreasing by the second step value; or

[0014] Within the specified switching frequency adjustment period, the target switching frequency is first determined by decreasing the starting frequency with the upper limit of the switching frequency and increasing it with the second step value. Then, the target switching frequency is determined by increasing the starting frequency with the lower limit of the switching frequency and increasing it with the first step value.

[0015] Optionally, the first step value and the second step value satisfy at least one of the following constraints, the constraints including:

[0016] The first step value and the second step value are positive integers that are not equal, and the first step value and the second step value belong to a specified interval;

[0017] The first step value and the second step value are coprime numbers.

[0018] Optionally, determining the target switching frequency of the switching transistor in each phase arm at the current moment based on the lower limit of the switching frequency and the upper limit of the switching frequency includes:

[0019] Determine multiple distinct integer frequency values ​​between the lower limit of the switching frequency and the upper limit of the switching frequency;

[0020] Determine the used integer frequency value within the specified switching frequency adjustment cycle at the current moment;

[0021] The target switching frequency is any one of the integer frequency values ​​other than the used integer frequency value among the plurality of different integer frequency values.

[0022] Optionally, controlling the switching transistors in each phase arm to turn on or off according to the target switching frequency of the switching transistors in each phase arm at the current time, so that the first battery pack and the second battery pack alternately charge and discharge to heat the power battery, includes:

[0023] Get the current ambient temperature;

[0024] Determine the target current for battery heating at the current moment based on the current ambient temperature;

[0025] The duty cycle of the switching transistor in each phase arm is determined based on the target switching frequency and the target current.

[0026] The switch in the bridge arm is turned on or off according to the duty cycle, so that the first battery pack and the second battery pack are alternately charged and discharged to heat the power battery.

[0027] Optionally, determining the duty cycle of the switching transistor in each phase arm based on the target switching frequency and the target current includes:

[0028] Obtain the current flowing through the specified switch;

[0029] The duty cycle of the switching transistor control signal is determined based on the target current, the current, and the target switching frequency.

[0030] Optionally, determining the target current for battery heating at the current moment based on the current ambient temperature includes:

[0031] The target heating current amplitude and target heating current frequency are determined based on the current ambient temperature.

[0032] The target current is determined based on the target heating current amplitude and the target heating current frequency.

[0033] A second aspect of this disclosure provides a battery heating system, including a power battery, a motor controller, a motor, a designated switch, and a designated controller. The power battery is formed by connecting a first battery pack and a second battery pack in series. The motor controller includes a multi-phase bridge arm, and the motor includes multi-phase windings. The midpoint of each phase bridge arm is connected to the first end of a phase winding. The second ends of each phase winding in the multi-phase winding are connected together and then connected to the first end of the designated switch. The second end of the designated switch is connected between the first battery pack and the second battery pack. The first busbar of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second busbar of the multi-phase bridge arm is connected to the negative terminal of the second battery pack.

[0034] The designated controller is used to implement the battery heating method described in the first aspect above.

[0035] A third aspect of this disclosure is to provide a vehicle that includes the battery heating system described in the second aspect above.

[0036] The above technical solution, by controlling the designated switch to close when battery heating is initiated, and obtaining the lower limit and upper limit of the switching frequency of the switching transistor in each phase arm; determining the target switching frequency of the switching transistor in each phase arm at the current moment based on the lower limit and upper limit of the switching frequency, wherein the target switching frequency of each switching transistor at the current moment is different from the first switching frequency at the previous sampling moment and the second switching frequency at the next sampling moment; controlling the switching transistor in the bridge arm to turn on or off according to the target switching frequency of the switching transistor in each phase arm at the current moment, so that the first battery pack and the second battery pack alternately charge and discharge to heat the power battery, can obtain a target switching frequency different from the first switching frequency at the previous sampling moment and the second switching frequency at the next sampling moment based on the lower limit and upper limit of the switching frequency, thereby effectively reducing the superposition of noise and magnetic field energy at the same frequency point.

[0037] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0038] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0039] Figure 1 This is a block diagram illustrating a battery heating system according to an exemplary embodiment of the present disclosure;

[0040] Figure 2This is a schematic diagram of a battery heating circuit shown in an exemplary embodiment of the present disclosure;

[0041] Figure 3 This is a flowchart illustrating a battery heating method according to an exemplary embodiment of the present disclosure;

[0042] Figure 4 It is based on Figure 3 The illustrated embodiment shows a flowchart of a battery heating method. Detailed Implementation

[0043] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0044] Figure 1 This is a block diagram illustrating an exemplary embodiment of a battery heating system, such as... Figure 1 As shown, the battery heating system includes a power battery 101, a motor controller 102, a motor 103, a designated switch 104, and a designated controller 105. The power battery 101 is formed by connecting a first battery pack 1011 and a second battery pack 1012 in series. The motor controller 102 includes a multi-phase bridge arm, and the motor 103 includes a multi-phase winding. The midpoint of each phase bridge arm is connected to the first end of a phase winding. The second ends of each phase winding in the multi-phase winding are connected together and then connected to the first end of the designated switch 104. The second end of the designated switch 104 is connected between the first battery pack 1011 and the second battery pack 1012. The first busbar of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second busbar of the multi-phase bridge arm is connected to the negative terminal of the second battery pack.

[0045] The designated switch 104 can be a contactor, a relay, or other automatic control switch. The designated controller 105 can be a vehicle controller or another control unit in the vehicle besides the vehicle controller. The motor controller 102 can be a reversible PWM rectifier. The number of bridge arms in the motor controller 102 is the same as the number of phases in the windings of the motor 103. The motor 103 can be a three-phase, five-phase, six-phase, or nine-phase permanent magnet synchronous motor, or a three-phase or higher asynchronous motor. Each phase winding can include n coil branches. The n coil branches of each phase winding are connected to form a phase endpoint. One coil branch of each phase winding is also connected to one coil branch of another phase winding to form n connection points. Figure 2 As shown, Figure 2This is a schematic diagram of a battery heating circuit according to an exemplary embodiment of the present disclosure. The motor controller 102 includes three bridge arms, and the motor 103 is a three-phase motor, including four sets of three-phase windings. The first set of windings includes coil branches A1, B1, and C1; the second set of windings includes coil branches A2, B2, and C2; the third set of windings includes coil branches A3, B3, and C3; and the fourth set of windings includes coil branches A4, B4, and C4. Each of the four coil branches (A1, A2, A3, and A4) of the A-phase winding is also connected to one coil branch of each of the other phase windings to form connection points a1, a2, a3, and a4. The designated controller 105 can obtain the current required for each phase of the motor by adjusting the PWM duty cycle of each phase bridge arm input to the motor controller 102.

[0046] Figure 3 This is a flowchart illustrating a battery heating method according to an exemplary embodiment of this disclosure; as shown below. Figure 3 As shown, this battery heating method can be achieved by... Figure 1 The designated controller 105 in the battery heating system shown executes, such as Figure 3 As shown, the battery heating method may include:

[0047] Step 301: If it is determined that battery heating will be started, control the designated switch to close, and obtain the lower limit value and upper limit value of the switching frequency of the switching transistor in each phase bridge arm.

[0048] In this step, the implementation method for determining the start of battery heating may be as follows: when it is determined that the vehicle is in a non-faulty state, in response to determining that the vehicle is in a parked state, a first temperature of the first battery pack and a second temperature of the second battery pack are obtained; when the first temperature and / or the second temperature are greater than a preset temperature threshold, it is determined that battery heating is started.

[0049] It should be noted that temperature sensors can be installed in the first and second battery packs to obtain the first and second temperatures. The above-described method for determining that the vehicle is in a non-faulty state can be as follows: if it is determined that the CAN communication is normal, the temperatures of the power battery, motor windings, and electronic control power switching devices are normal, and no hardware faults are detected in the vehicle control unit, battery system, or electronic control system, then the vehicle is determined to be in a non-faulty state.

[0050] In addition, the lower and upper limits of the switching frequency can be parameters given at the factory of the motor controller, or they can be obtained through experimental testing. For example, using an NVH (Noise, Vibration, Harshness) microphone testing device on a motor assembly bench, different switching frequencies can be fixed. Under the conditions of maximum heating current amplitude and optimal heating current frequency, the lower limit of the switching frequency f of the switching transistor can be determined from two dimensions: the subjective electromagnetic howling perceived by multiple testers and the test values ​​of the microphone testing device. min The inventors discovered that the higher the switching frequency, the better the sinusoidal nature of the motor phase current, which means less vibration in the motor winding coils and lower noise. Therefore, the highest switching frequency currently designed for the motor controller 102 can be selected as the upper limit value f of the switching frequency of the switching transistor. max .

[0051] Step 302: Determine the target switching frequency of the switching transistor in each phase arm at the current time based on the lower limit of the switching frequency and the upper limit of the switching frequency, wherein the target switching frequency of each switching transistor at the current time is different from the first switching frequency of the switching transistor at the previous sampling time and the second switching frequency at the next sampling time.

[0052] In this step, one possible implementation is to determine the target switching frequency in an incremental and / or decremental manner within the switching frequency adjustment range corresponding to the lower limit and the upper limit of the switching frequency.

[0053] For example, within each switching frequency adjustment cycle, the switching frequency at each moment is determined by incrementing the lower limit of the switching frequency as the starting frequency and incrementing by a first step value, wherein the switching frequency at each moment is less than the upper limit of the switching frequency; or, within each switching frequency adjustment cycle, the switching frequency at each moment is determined by decrementing the upper limit of the switching frequency as the starting frequency and decrementing by a second step value, wherein the switching frequency at each moment is greater than the lower limit of the switching frequency; alternatively, within each switching frequency adjustment cycle, the switching frequency can be determined by first incrementing the lower limit of the switching frequency as the starting frequency and incrementing by a first step value, then by decrementing the upper limit of the switching frequency as the starting frequency and decrementing by a second step value; or, within each switching frequency adjustment cycle, the switching frequency can be determined by first incrementing the upper limit of the switching frequency as the starting frequency and decrementing by a second step value, then by incrementing the lower limit of the switching frequency as the starting frequency and incrementing by a first step value.

[0054] It should be noted that the first step value and the second step value satisfy at least one of the following restrictions, the restrictions include: the first step value and the second step value are not equal positive integers, and the first step value and the second step value belong to a specified interval; the first step value and the second step value are prime numbers, and the specified interval can be a subset of [1, 9] or any positive integer interval.

[0055] In this step, another possible implementation is as follows: determine a plurality of different integer frequency values ​​between the lower limit of the switching frequency and the upper limit of the switching frequency; determine the used integer frequency value within the specified switching frequency adjustment cycle at the current moment; and take any integer frequency value other than the used integer frequency value among the plurality of different integer frequency values ​​as the target switching frequency.

[0056] For example, if the lower limit of the switching frequency is 1 and the upper limit of the switching frequency is 15, then the integer frequency values ​​between the lower limit of the switching frequency and the upper limit of the switching frequency include 1, 2, 3...15. If 15, 14, 11, 7 and 9 have been used in the current cycle, then any integer frequency value other than 15, 14, 11, 7 and 9 from 1 to 15 can be used as the target switching frequency.

[0057] By setting different first and second step values, it is possible to effectively avoid the problem of noise and magnetic field energy superposition at the same frequency when the switching frequency is the same at different times, thereby effectively improving the driving experience of vehicle users.

[0058] Step 303: Control the switching transistors in each phase arm to be turned on or off according to the target switching frequency of the switching transistors in each phase arm at the current time, so that the first battery pack and the second battery pack are alternately charged and discharged to heat the power battery.

[0059] In this step, the current ambient temperature can be obtained; the target current for battery heating at the current moment can be determined based on the current ambient temperature; the duty cycle of the switching transistor in each phase arm can be determined based on the target switching frequency and the target current; and the switching transistor in the arm can be turned on or off based on the duty cycle, so that the first battery pack and the second battery pack alternately charge and discharge to heat the power battery.

[0060] The above technical solution can obtain a target switching frequency that is different from the first switching frequency of the switching transistor at the previous sampling time and the second switching frequency at the next sampling time, based on the lower limit and upper limit of the switching frequency, thereby effectively reducing the superposition of noise and magnetic field energy at the same frequency point.

[0061] Preferably, determining the target switching frequency within the switching frequency adjustment range corresponding to the lower and upper limits of the switching frequency, in an incremental and / or decremental manner, may include:

[0062] Determine the specified switching frequency adjustment period at the current time; within the specified switching frequency adjustment period, first use the lower limit of the switching frequency as the starting frequency to increase, and then use the first step value to increase to determine the target switching frequency; then use the upper limit of the switching frequency as the starting frequency to decrease, and then use the second step value to decrease to determine the target switching frequency; or, within the specified switching frequency adjustment period, first use the upper limit of the switching frequency as the starting frequency to decrease, and then use the second step value to increase to determine the target switching frequency; then use the lower limit of the switching frequency as the starting frequency to increase, and then use the first step value to increase to determine the target switching frequency.

[0063] Wherein, the first step value and the second step value satisfy at least one of the following constraints, the constraints including: the first step value and the second step value are not equal positive integers; the first step value and the second step value are prime numbers; the first step value and the second step value belong to a specified interval of positive integers.

[0064] Figure 4 It is based on Figure 3 The illustrated embodiment shows a flowchart of a battery heating method; as shown Figure 4 As shown, Figure 3 The implementation method described in step 303, which controls the switching transistors in each phase arm to be turned on or off according to the target switching frequency of the switching transistors in each phase arm at the current time, so that the first battery pack and the second battery pack are alternately charged and discharged to heat the power battery, may include:

[0065] Step 3031: Obtain the current ambient temperature.

[0066] In this step, the ambient temperature at the current moment can be collected by the ambient temperature sensor installed on the vehicle to obtain the current ambient temperature.

[0067] Step 3032: Determine the target current for battery heating at the current moment based on the current ambient temperature.

[0068] This step can be achieved through the steps shown in S1 and S2 below:

[0069] S1, determine the target heating current amplitude and target heating current frequency based on the current ambient temperature.

[0070] In one possible implementation, both the target heating current amplitude and the target heating current frequency can be preset empirical values. For example, a preset database stores the target heating current amplitude and target heating current frequency at different ambient temperatures, and the target heating current amplitude and target heating current frequency corresponding to the current ambient temperature are obtained by looking up the table.

[0071] Another possible implementation is that the target heating current amplitude can be determined by acquiring the first maximum charge / discharge current of the first battery pack and the second maximum charge / discharge current of the second battery pack within a preset historical time period, and using the smaller of the first maximum charge / discharge current and the second maximum charge / discharge current as the target heating current amplitude. The implementation for determining the target heating current frequency can be as follows: acquiring the first impedance of the first battery pack and the second impedance of the second battery pack at the current ambient temperature; determining the first current frequency corresponding to the current fastest temperature rise rate of the first battery pack based on the current ambient temperature and the first impedance; determining the second current frequency corresponding to the current fastest temperature rise rate of the second battery pack based on the current ambient temperature and the second impedance; and using the larger of the first current frequency and the second current frequency as the target heating current frequency, wherein the target heating current frequency is the heating current frequency of the current fastest temperature rise rate of the power battery.

[0072] It should be noted that the battery management system can store charging and discharging data of the first and second battery packs within a specified time period. This charging and discharging data typically includes information such as charging and discharging current, voltage status, and remaining capacity. The first maximum charging and discharging current can be obtained by retrieving the maximum charging and discharging current of the first battery pack within the preset historical time period from the battery management system; and the second maximum charging and discharging current can be obtained by retrieving the maximum charging and discharging current of the second battery pack within the preset historical time period.

[0073] S2, determine the target current based on the target heating current amplitude and the target heating current frequency.

[0074] For example, if the target heating current amplitude is I1A (RMS value) and the heating current frequency with the fastest temperature rise rate (i.e., the target heating current frequency) is f Tvmax If the Hz value is 1, then the target current is I. _ref =I1*sin(2πf Tvmax *t), where t is the battery heating time.

[0075] Step 3033: Determine the duty cycle of the switching transistor in each phase arm based on the target switching frequency and the target current.

[0076] In this step, the current flowing through the designated switch can be obtained; the duty cycle of the switch control signal can be determined based on the target current, the current current, and the target switch frequency.

[0077] For example, if the target current is I _ref The current flowing through the designated switch is used as the feedback current to provide the target heating current I. _ref The feedback current (which can be the neutral line current I from the motor) N_fdk The error current I is obtained by subtracting the error current. _err After passing through the PR controller or PI controller, the control voltage value U of each bridge arm of the motor controller corresponding to the battery heating current is obtained. Nref The control voltage value U of each phase bridge arm Nref The PWM duty cycle of the switching transistors in each phase bridge arm is obtained by modulating the carrier wave with the target switching frequency. It should be noted that the current flowing through the specified switch is the N-line current I from the motor. N_fdk The current can be obtained by inverting the N-line current using a current Hall sensor, or by calculating the current of the motor phases.

[0078] Step 3034: Control the switch tube in the bridge arm to turn on or off according to the duty cycle, so that the first battery pack and the second battery pack are alternately charged and discharged to heat the power battery.

[0079] In this step, the switching transistor can be controlled by providing a PWM signal with the specified duty cycle, so that it is turned on when the PWM signal is high and turned off when the PWM signal is low.

[0080] The above technical solution determines the duty cycle of the switching transistor in each phase arm based on the target switching frequency and the target current, and controls the switching transistor in the arm to be turned on or off according to the duty cycle to heat the power battery, thereby effectively ensuring the battery heating efficiency.

[0081] Another exemplary embodiment of this disclosure provides a vehicle, the vehicle comprising the above... Figure 1 The aforementioned battery heating system not only ensures efficient battery heating but also effectively reduces the superposition of noise and magnetic field energy at the same frequency.

[0082] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0083] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0084] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A battery heating method, characterized in that, A designated controller is applied to a battery heating system, the battery heating system including a power battery, a motor controller, a motor, a designated switch, and the designated controller. The power battery is formed by connecting a first battery pack and a second battery pack in series. The motor controller includes a multi-phase bridge arm, the motor includes multi-phase windings, the midpoint of each phase bridge arm is connected to the first end of a phase winding, the second ends of each phase winding in the multi-phase windings are connected together and then connected to the first end of the designated switch, the second end of the designated switch is connected between the first battery pack and the second battery pack, the first bus terminal of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second bus terminal of the multi-phase bridge arm is connected to the negative terminal of the second battery pack; the method includes: In response to determining that the vehicle is in a parked state, a first temperature of the first battery pack and a second temperature of the second battery pack are obtained; if the first temperature and / or the second temperature are greater than a preset temperature threshold, it is determined to start battery heating; If it is determined that the battery heating will be started, the designated switch will be closed, and the lower limit value and upper limit value of the switching frequency of the switching transistor in each phase arm will be obtained. The target switching frequency of the switching transistor in each phase arm at the current moment is determined based on the lower limit value of the switching frequency and the upper limit value of the switching frequency, wherein the target switching frequency of each switching transistor at the current moment is different from the first switching frequency of the switching transistor at the previous sampling moment and the second switching frequency at the next sampling moment. The switching transistors in each phase arm are controlled to be turned on or off according to the target switching frequency of the switching transistors in each phase arm at the current moment, so that the first battery pack and the second battery pack are alternately charged and discharged to heat the power battery. Determining the target switching frequency of the switching transistor in each phase arm at the current moment based on the lower limit and the upper limit of the switching frequency includes: Within the switching frequency adjustment range corresponding to the lower limit and the upper limit of the switching frequency, the target switching frequency is determined in an incremental and / or decremental manner. Determining the target switching frequency in an incremental and / or decremental manner within the switching frequency adjustment range corresponding to the lower and upper limits of the switching frequency includes: Determine the current switching frequency adjustment cycle; Within the specified switching frequency adjustment period, the target switching frequency is first determined by increasing the lower limit of the switching frequency as the starting frequency and increasing by the first step value; then, the target switching frequency is determined by decreasing the upper limit of the switching frequency as the starting frequency and decreasing by the second step value; or Within the specified switching frequency adjustment period, the target switching frequency is first determined by decreasing the starting frequency with the upper limit of the switching frequency and increasing it with the second step value. Then, the target switching frequency is determined by increasing the starting frequency with the lower limit of the switching frequency and increasing it with the first step value. The first step value and the second step value satisfy at least one of the following constraints, the constraints including: The first step value and the second step value are positive integers that are not equal, and the first step value and the second step value belong to a specified interval; The first step value and the second step value are coprime numbers.

2. The battery heating method according to claim 1, characterized in that, Determining the target switching frequency of the switching transistor in each phase arm at the current moment based on the lower limit and the upper limit of the switching frequency includes: Determine multiple distinct integer frequency values ​​between the lower limit of the switching frequency and the upper limit of the switching frequency; Determine the used integer frequency value within the specified switching frequency adjustment cycle at the current moment; The target switching frequency is any one of the integer frequency values ​​other than the used integer frequency value among the plurality of different integer frequency values.

3. The battery heating method according to claim 1, characterized in that, The step of controlling the switching transistors in each phase arm to be turned on or off according to the target switching frequency of the switching transistors in each phase arm at the current time, so as to alternately charge and discharge the first battery pack and the second battery pack to heat the power battery, includes: Get the current ambient temperature; Determine the target current for battery heating at the current moment based on the current ambient temperature; The duty cycle of the switching transistor in each phase arm is determined based on the target switching frequency and the target current. The switch in the bridge arm is turned on or off according to the duty cycle, so that the first battery pack and the second battery pack are alternately charged and discharged to heat the power battery.

4. The battery heating method according to claim 3, characterized in that, The step of determining the duty cycle of the switching transistor in each phase arm based on the target switching frequency and the target current includes: Obtain the current flowing through the specified switch; The duty cycle of the switching transistor control signal is determined based on the target current, the current, and the target switching frequency.

5. The battery heating method according to claim 3, characterized in that, Determining the target current for battery heating at the current moment based on the current ambient temperature includes: The target heating current amplitude and target heating current frequency are determined based on the current ambient temperature. The target current is determined based on the target heating current amplitude and the target heating current frequency.

6. A battery heating system, characterized in that, The system includes a power battery, a motor controller, a motor, a designated switch, and a designated controller. The power battery is formed by connecting a first battery pack and a second battery pack in series. The motor controller includes a multi-phase bridge arm, and the motor includes multi-phase windings. The midpoint of each phase bridge arm is connected to the first end of a phase winding. The second ends of each phase winding in the multi-phase winding are connected together and then connected to the first end of the designated switch. The second end of the designated switch is connected between the first battery pack and the second battery pack. The first busbar of the multi-phase bridge arm is connected to the positive terminal of the first battery pack, and the second busbar of the multi-phase bridge arm is connected to the negative terminal of the second battery pack. The designated controller is used to implement the battery heating method according to any one of claims 1-5.

7. A vehicle, characterized in that, The vehicle includes the battery heating system as described in claim 6.

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