Power battery heating method, power battery heating device and electric vehicle

Abstract

The application discloses a power battery heating method, a power battery heating device and an electric vehicle. The maximum alternating current power that each driving unit can output under different target charge-discharge frequencies and corresponding vibration noise indexes are acquired, and the target charge-discharge frequency corresponding to the maximum sum of the maximum alternating current power of each driving unit when the vibration noise indexes are less than a preset threshold is determined as a frequency reference value. The alternating phase of the bus current of any one of the driving units is acquired, and the acquired alternating phase of the bus current is determined as a phase reference value. Then, the charge-discharge frequencies of the driving units are adjusted according to the frequency reference value, so that the charge-discharge frequencies of the driving units are consistent with the frequency reference value. The alternating phases of the bus currents of the driving units are adjusted according to the phase reference value, so that the alternating phases of the bus currents of the driving units are consistent with the phase reference value. The application aims to improve the heating efficiency of the multi-driving-unit power battery.

Description

Technical Field

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

[0002] In electric vehicles, batteries cannot be charged in low-temperature environments. Therefore, the batteries are heated while the vehicle is stationary before charging. A common method for static heating is to generate a high-frequency alternating current in the battery by alternating the power of the motor. This heat is then generated by the internal resistance of the battery, and is also known as charge-discharge heating.

[0003] With the rapid development of the electric vehicle industry, in terms of the powertrain structure of the entire vehicle, in addition to the most common single-motor drive, dual-motor, tri-motor, and quad-motor drive solutions have also emerged. Dual-motor drive is commonly used in four-wheel drive vehicles, while tri-motor and quad-motor drive are also used in distributed drive models. However, current electric vehicle battery heating solutions still use a single drive unit to generate heating power, failing to leverage the advantages of multi-drive electric vehicles. Therefore, the heating power of the power battery in multi-drive electric vehicles needs to be improved to enhance heating efficiency. Summary of the Invention

[0004] The main objective of this invention is to provide a power battery heating method, a power battery heating device, and an electric vehicle, which aims to improve the heating power of multi-drive unit power batteries and thus enhance their heating efficiency.

[0005] To achieve the above objectives, the present invention proposes a power battery heating method, applicable to electric vehicles with multiple drive units, the power battery heating method comprising:

[0006] The maximum AC power output by each drive unit at different target charging and discharging frequencies and the corresponding vibration and noise indicators are obtained. The target charging and discharging frequency that meets the condition that the vibration and noise indicators are less than a preset threshold and the sum of the maximum AC power output by each drive unit is the maximum value is determined as the frequency reference value.

[0007] The AC phase of the bus current of any one of the drive units is obtained, and the obtained AC phase of the bus current is determined as the phase reference value.

[0008] The charging and discharging frequencies of each driving unit are adjusted according to the frequency reference value so that the charging and discharging frequencies of each driving unit are consistent with the frequency reference value; and

[0009] The AC phase of the bus current of each drive unit is adjusted according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value.

[0010] Optionally, the step of obtaining the target charging and discharging frequency corresponding to the maximum AC power output by each driving unit at different target charging and discharging frequencies, and determining the target charging and discharging frequency corresponding to the maximum AC power as the frequency reference value, specifically includes:

[0011] The sum of AC power output by multiple drive units at different target charging and discharging frequencies is obtained, and the sum of multiple AC power corresponding to different target charging and discharging frequencies is obtained.

[0012] Determine the maximum value among the sums of multiple AC power values;

[0013] The target charging and discharging frequency corresponding to the maximum value among the sums of multiple AC power values ​​is determined as the frequency reference value.

[0014] Optionally, adjusting the charging and discharging frequency of each driving unit according to the frequency reference value so that the charging and discharging frequency of each driving unit is consistent with the frequency reference value includes:

[0015] The charging and discharging frequency of each driving unit is adjusted according to the frequency reference value, including the rising slope of the AC power of each driving unit, the peak value of the AC power of the driving unit, and the time when the AC power of the driving unit is zero, so that the charging and discharging frequency of each driving unit is consistent with the frequency reference value.

[0016] Optionally, the step of obtaining the AC phase of the bus current of any one of the driving units and determining the obtained AC phase of the bus current as a phase reference value specifically includes:

[0017] One of the plurality of driving units is designated as the master driving unit, and the remaining driving units are designated as slave driving units. The phase of the master driving unit is obtained and set as the phase reference value.

[0018] Optionally, the step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes:

[0019] Select one of the multiple drive units as the target control object;

[0020] The selected target control object is turned on to heat the battery, while the battery heating function of other drive units is turned off.

[0021] Adjust the AC phase of the bus current of the target controlled object until the output current of the multi-drive unit power battery is at its maximum value, then return to the step of selecting one of the multiple slave drive units as the target controlled object, until all the slave drive units have been selected.

[0022] Optionally, the step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes:

[0023] Select one of the multiple drive units as the target control object;

[0024] The selected target control object is turned on to heat the battery, while the battery heating function of other drive units is turned off.

[0025] Adjust the AC phase of the bus current of the target controlled object until the fluctuation amplitude of the bus voltage of the target controlled object reaches its maximum value, then return to the step of selecting one of the multiple slave drive units as the target controlled object, until all the slave drive units have been selected.

[0026] Optionally, the step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes:

[0027] Select one of the multiple drive units as the target control object;

[0028] Obtain the phase reference value and timestamp of the main drive unit at a preset time;

[0029] The desired phase change of the target controlled object is determined based on the phase reference value and timestamp of the main drive unit at a preset time, and the AC phase and timestamp of the bus current of the target controlled object at a preset time.

[0030] Adjust the AC phase of the bus current of the target controlled object according to the phase change until the AC phase of the adjusted bus current of the target controlled object is consistent with the phase reference value. Then, return to the step of selecting one of the multiple slave drive units as the target controlled object until all the slave drive units have been selected.

[0031] Optionally, a transition carrier frequency period is inserted into the PWM control signal of the target controlled object to adjust the AC phase of the bus current of the target controlled object so that the AC phase of the bus current of the target controlled object is consistent with the phase reference value.

[0032] Optionally, the step of inserting a transition carrier frequency period into the PWM control signal of the target controlled object to adjust the AC phase of the bus current of the target controlled object so that the AC phase of the bus current of the target controlled object is consistent with the phase reference value specifically includes:

[0033] Obtain the initial period and initial carrier frequency from the PWM control signal of the target controlled object;

[0034] The carrier frequency of the transition carrier frequency period is determined based on the phase reference value, the AC phase of the bus current of the target controlled object, and the frequency reference value.

[0035] The transition carrier frequency period of the target controlled object is determined based on the initial period, the initial carrier frequency, and the carrier frequency of the transition carrier frequency period.

[0036] The target control object is turned on to heat the battery, and the transition carrier frequency period is used as the period of the PWM control signal of the target control object when the heating time of the target control object is one initial cycle.

[0037] Re-enable the target control object to heat the battery, and use the initial period as the period of the PWM control signal of the target control object when the heating duration of the target control object is one transition carrier frequency cycle.

[0038] The present invention also proposes a power battery heating device, the power battery heating device comprising:

[0039] Memory;

[0040] Processor; and

[0041] A power battery heating control program stored in a memory and executable on a processor, wherein the processor executes the power battery heating control program to implement the power battery heating method described above.

[0042] The present invention also proposes an electric vehicle, which includes a multi-drive unit power battery and the power battery heating device described above.

[0043] In the power battery heating method of the present invention, the maximum AC power output of each drive unit at different target charge-discharge frequencies and the corresponding vibration and noise indicators are first obtained. The target charge-discharge frequency corresponding to the condition that the vibration and noise indicators are less than a preset threshold and the sum of the maximum AC power output of each drive unit is the maximum value is determined as the frequency reference value. Then, the AC phase of the bus current of any one of the drive units is obtained, and the obtained AC phase of the bus current is determined as the phase reference value. Then, the charge-discharge frequency of each drive unit is adjusted according to the frequency reference value so that the charge-discharge frequency of each drive unit is consistent with the frequency reference value. And the AC phase of the bus current of each drive unit is adjusted according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value. In this way, the charge-discharge frequency and phase of multiple drive units are consistent, so that multiple drive units coordinate to heat the power battery and maximize the heating power, thereby shortening the heating time of the multi-drive unit power battery and improving the heating efficiency of the multi-drive unit power battery. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0045] Figure 1 A simplified topology diagram for multiple drive units;

[0046] Figure 2 This is a flowchart of an embodiment of the power battery heating method of the present invention;

[0047] Figure 3 This is a flowchart of another embodiment of the power battery heating method of the present invention;

[0048] Figure 4 This is a flowchart of another embodiment of the power battery heating method of the present invention;

[0049] Figure 5 This is a flowchart of another embodiment of the power battery heating method of the present invention;

[0050] Figure 6 This is a flowchart of another embodiment of the power battery heating method of the present invention;

[0051] Figure 7 This is a single-drive unit three-phase four-bridge arm equivalent H-bridge circuit;

[0052] Figure 8The current waveform of a single-drive unit with three phases and four bridge arms;

[0053] Figure 9 The AC power waveform is shown when the phase is adjusted by the PWM carrier frequency period while the carrier frequency remains constant.

[0054] Figure 10 This is an AC power waveform diagram when the phase is adjusted by inserting a transition carrier frequency period according to the present invention.

[0055] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0057] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0058] It should be noted that step designations such as S100 and S200 are used in this document for the purpose of more clearly and concisely describing the corresponding content, and do not constitute a substantial limitation on the order. In specific implementation, those skilled in the art may execute S200 first and then S100, etc., but these should all be within the protection scope of this application.

[0059] A typical power battery charging and discharging heating scheme for a single-drive unit includes a power battery, a switching module, and a motor. The most commonly used switching module is a three-phase bridge. In this scheme, the motor's three-phase windings are not in phase, and the current frequency is high, leading to excessive motor vibration and noise. However, in a three-phase four-bridge scheme, the switching states of the corresponding bridge arms are consistent, resulting in completely equal three-phase currents in the motor windings. After coordinate transformation, the dq currents are found to be zero, thus the output torque is always zero, preventing vibration and noise. Therefore, a three-phase four-bridge charging and discharging heating scheme can be used.

[0060] Currently, multi-drive unit solutions are very common in vehicles. For the heating system of a multi-drive unit power battery, each drive unit can be considered a current source, and the entire system consists of multiple current sources connected in parallel. (Reference) Figure 1 , Figure 1 This is a simplified topology diagram equivalent to multiple drive units, by Figure 1 It can be determined that the battery's operating current is:

[0061] i bat =i1+i2+...+i N ,

[0062]

[0063] Among them, i n P represents the bus current of the nth drive unit, where N is the total number of drive units; n It is the effective value of the AC power of the nth drive unit.

[0064] Obviously, when the bus currents i1, i2, ..., i corresponding to each drive unit are... n When the frequency and phase are consistent, the total battery current i bat The effective value is maximized, thus maximizing the heating power of the multi-drive unit power battery. Conversely, if i1, i2, ..., i n If the frequencies or phases of i1 and i2 are different, the bus currents of each drive unit may cancel each other out at certain times, which will weaken the heating power of the multi-drive unit power battery. For a heating system of a dual-drive unit power battery, if i1 and i2 have the same frequency but opposite phase, then i bat = i1 + i2. Even if the values ​​of i1 and i2 are large, the heating power of the dual-drive unit power battery is still very small. Therefore, in order to ensure that the heating power of the multi-drive unit power battery is as large as possible to achieve better heating efficiency, it is necessary to ensure that the AC power frequency and phase of each drive unit are consistent.

[0065] Therefore, this invention proposes a power battery heating method, applicable to multi-drive unit power batteries, with reference to... Figure 2 The power battery heating method includes:

[0066] Step S100: Obtain the maximum AC power output by each drive unit at different target charging and discharging frequencies and the corresponding vibration and noise index. Determine the target charging and discharging frequency that satisfies the condition that the vibration and noise index is less than a preset threshold and the sum of the maximum AC power output by each drive unit is the maximum value as the frequency reference value.

[0067] Step S200: Obtain the AC phase of the bus current of any one of the drive units, and determine the obtained AC phase of the bus current as the phase reference value;

[0068] Step S300: Adjust the charging and discharging frequency of each driving unit according to the frequency reference value, so that the charging and discharging frequency of each driving unit is consistent with the frequency reference value; and

[0069] The AC phase of the bus current of each drive unit is adjusted according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value.

[0070] In this embodiment, the power battery heating method of the present invention can be applied to a multi-drive unit power battery heating device. The power battery heating device integrates a memory for storing the power battery heating method of the present invention, and a processor for executing the power battery heating method of the present invention. The power battery heating device can be implemented using a main controller, such as an MCU, DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), PLC, or SOC (System on Chip).

[0071] Understandably, to improve work efficiency, each drive unit can be equipped with a corresponding power battery heating device, meaning each drive unit has a separate main controller to execute the power battery heating control program corresponding to the power battery heating method of this invention. Taking an MCU as an example, each MCU can integrate a frequency reference value calculation module, a frequency adjustment module, a phase reference value calculation module, and a phase adjustment module. These modules are used to perform corresponding operations on their respective drive units according to the power battery heating method of this invention. The frequency and phase reference values ​​can be pre-set by the developers, or the frequency reference value calculation module for each drive unit can calculate the AC power value of its respective drive unit at different charging and discharging frequencies to obtain the total AC power at different charging and discharging frequencies, thereby obtaining the charging and discharging frequency corresponding to the maximum value of the total AC power, and setting this as the frequency reference value.

[0072] It should be noted that for the charging and discharging heating scheme of a three-phase bridge, the selection of the frequency reference value needs to consider both heating power and NVH (Noise, Vibration, and Harshness) factors. Heating power refers to the allowable AC power output of each drive unit at different charging and discharging frequencies. For example, increasing the current freewheeling time can increase the charging and discharging cycle, thereby reducing the charging and discharging frequency and the AC power. NVH arises because the three-phase windings of the three-phase bridge motor are not in phase, and the current frequency is high, leading to excessive motor vibration and noise, which can cause potential vibration and noise problems. If the charging and discharging frequency is close to the resonant frequency of the motor or capacitor, NVH issues will occur. Therefore, the frequency reference value f... ref The selection of [the appropriate power source] aims to maximize the heating power of the multi-drive unit power battery while ensuring that the NVH (Noise, Vibration, and Harshness) of each drive unit meets the requirements. That is:

[0073]

[0074] Among them, P maxn (f ref ) refers to the nth driving unit in f ref The maximum AC power value that can be achieved at the charging and discharging frequency, N n (f ref ) refers to the nth driving unit in f ref The noise level at the charging and discharging frequency, N lim This refers to the maximum allowable noise level for each drive unit.

[0075] As described above, when the vibration and noise levels of each drive unit are less than a preset threshold (i.e., NVH requirements are met), the target charge-discharge frequency corresponding to the maximum sum of AC power of each drive unit at different target charge-discharge frequencies is used as the frequency reference value. Then, the charge-discharge frequency of each drive unit is adjusted to ensure it matches the frequency reference value. The preset threshold is set in advance by the R&D personnel. Furthermore, since the specific phase value is not important, the key is to ensure the phase of each drive unit is the same. Therefore, the phase reference value can be set in advance by the R&D personnel or, based on actual conditions, the phase of one of the multiple drive units can be selected as the phase reference value. The phase of each drive unit is then adjusted to ensure consistency among the phase reference values. In this way, the heating power of the multi-drive unit power battery is at its maximum, resulting in good heating efficiency and meeting the NVH requirements of each drive unit.

[0076] It should be noted that for a three-phase four-arm charging and discharging heating scheme, the selection of the frequency reference value only needs to consider the heating power, and does not need to consider vibration and noise indicators. That is, the charging and discharging frequency corresponding to the maximum value of the sum of AC power at different charging and discharging frequencies can be used as the frequency reference value.

[0077] Specifically, each drive unit's motor is equipped with a power battery heating device, such as a main controller (MCU). The main controller can control the frequency reference value calculation module to calculate the maximum AC power output of its own drive unit at different target charge / discharge frequencies. The vibration and noise levels of each drive unit operating at the target charge / discharge frequency must meet NVH requirements. The target charge / discharge frequency can be preset by the R&D personnel. For example, the main controller can control the frequency reference value calculation module to calculate the maximum AC power output of its own drive unit at different target charge / discharge frequencies and the corresponding vibration and noise levels. Then, the target charge / discharge frequency corresponding to when the vibration and noise levels of each drive unit are less than a preset threshold and the sum of the maximum AC power outputs of all drive units reaches the maximum value is selected as the frequency reference value. Alternatively, a frequency variation range that meets NVH requirements can be pre-set. This allows the frequency reference value calculation module of each drive unit to independently calculate the AC power output of its respective drive unit at different target charge / discharge frequencies within the frequency variation range, thereby obtaining the maximum AC power. This, in turn, yields the sum of AC power output by multiple drive units at different target charge / discharge frequencies. The maximum value among these sums is then determined, and the target charge / discharge frequency corresponding to this maximum value is set as the frequency reference value. The charge / discharge frequencies of each drive unit are then adjusted according to the frequency reference value to ensure consistency with the frequency reference value. Furthermore, the phases of each drive unit are adjusted according to the phase reference value to ensure consistency with the phase reference values. The specific numerical value of the phase reference value is not critical; the key is that the phases of all drive units remain consistent.

[0078] Taking a dual-drive unit in a vehicle equipped with front and rear wheels as an example, each uses a three-phase bridge as its switching module. The frequency reference value calculation module in the main controller of the front drive calculates the AC power of the front drive at the target charging and discharging frequencies of f1, f2, and f3 as 0.9KW, 0.95KW, and 1KW, respectively, and calculates the vibration and noise index of the front drive at the target charging and discharging frequencies of f1, f2, and f3. The frequency reference value calculation module in the main controller of the rear drive calculates the AC power of the rear drive at the target charging and discharging frequencies of f1, f2, and f3 as 0.95KW, 1KW, and 0.8KW, respectively, and calculates the vibration and noise index of the rear drive at the target charging and discharging frequencies of f1, f2, and f3. If the vibration and noise indices of both the front-drive and rear-drive units at target charging and discharging frequencies f1, f2, and f3 are all less than the preset threshold, meaning the NVH requirements are met, then the total AC power at the target charging and discharging frequencies f1, f2, and f3 is calculated to be 1.85KW, 1.95KW, and 1.8KW, respectively. Therefore, the maximum value among the multiple AC power sums is 1.95KW, so f2 corresponding to 1.95KW should be used as the frequency reference value. If, at target charging and discharging frequencies f1, f2, and f3, the vibration and noise indices of either the front-drive or rear-drive unit at the target charging and discharging frequency f2 are greater than the preset threshold, then the target charging and discharging frequency f2 cannot be used as the frequency reference value, and f1 should be selected as the frequency reference value. Then, the frequency adjustment module in the main controller of each drive unit adjusts its own charging and discharging frequency to be consistent with the frequency reference value, and the phase adjustment module of each drive unit adjusts its own phase to be consistent with the phase reference value based on the phase reference value.

[0079] In the power battery heating method of the present invention, the maximum AC power output of each drive unit at different target charge-discharge frequencies and the corresponding vibration and noise indicators are first obtained. The target charge-discharge frequency corresponding to the condition that the vibration and noise indicators are less than a preset threshold and the sum of the maximum AC power output of each drive unit is the maximum value is determined as the frequency reference value. Then, the AC phase of the bus current of any one of the drive units is obtained, and the obtained AC phase of the bus current is determined as the phase reference value. Then, the charge-discharge frequency of each drive unit is adjusted according to the frequency reference value so that the charge-discharge frequency of each drive unit is consistent with the frequency reference value. And the AC phase of the bus current of each drive unit is adjusted according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value. In this way, the charge-discharge frequency and phase of multiple drive units are consistent, so that multiple drive units coordinate to heat the power battery and maximize the heating power, thereby shortening the heating time of the multi-drive unit power battery and improving the heating efficiency of the multi-drive unit power battery.

[0080] It should be noted that, taking a three-phase four-arm bridge as an example, its equivalent circuit diagram is as follows: Figure 7 As shown, each bridge arm adopts a complementary conduction mode. The working process is divided into four stages: 1. When T135 is on and T7 is off, the battery charges inductor L through T135 and T8, and the inductor current rises from 0 to Imax. 2. When T135 is off and T7 is off, the inductor current freewheels through T8 and D246 and remains constant. At this time, there is no energy exchange between the inductor and the battery. 3. When T135 is off and T7 is on, the inductor current freewheels through D7 and D246 and decreases from Imax. At this time, the inductor charges the battery. 4. When T135 is on and T7 is on, the inductor current freewheels through D7 and T135 and remains constant. At this time, there is no energy exchange between the inductor and the battery. During this process, the relationship between the current of the three-phase windings, the motor center point current, and the battery current under different states is illustrated in the diagram below. Figure 8 As shown in Figure a, the motor center point current is shown; Figure b, the motor three-phase current is shown; and Figure c, the battery current is shown. It can be seen that in states 1 and 3, the current slope is basically constant. This is because the motor resistance is relatively small, and it can be approximated as a purely inductive load. The current rise and fall slope k is related to the total inductance L and the bus voltage U. dc It is related to the slope k = U dc / L. The heating of the motor's three-phase windings limits the three-phase current, which in turn limits the neutral point current and the battery current. Let's assume the maximum neutral point current is I. max Furthermore, let the sum of the times in states 2 and 4 be T0, i.e., let the freewheeling time be T0. Then the battery charge / discharge cycle is: T1 = I max / k×2+T0. Therefore, change I max , k or T0 can both change the charging and discharging frequency.

[0081] Therefore, in one embodiment of the present invention, adjusting the charging and discharging frequency of each driving unit according to a frequency reference value so that the charging and discharging frequency of each driving unit is consistent with the frequency reference value includes:

[0082] The charging and discharging frequency of each driving unit is adjusted according to the frequency reference value, including the rising slope of the AC power of each driving unit, the peak value of the AC power of the driving unit, and the time when the AC power of the driving unit is zero, so that the charging and discharging frequency of each driving unit is consistent with the frequency reference value.

[0083] In this embodiment, referring to the above embodiments, a dual-drive unit is used as an example. Each drive unit uses a three-phase bridge as a switching module. The power battery heating device controls the frequency reference value calculation modules of the front drive and rear drive to calculate the AC power corresponding to different target charge and discharge frequencies. Then, the maximum value among the sums of multiple AC power values ​​is obtained. The target charge and discharge frequency corresponding to the maximum sum of AC power values ​​is used as the frequency reference value, that is, the frequency corresponding to the maximum sum of AC power that each drive unit can output at different target charge and discharge frequencies. The vibration and noise index of each drive unit when operating at the frequency reference value must meet the NVH requirements. If the NVH of any drive unit operating at the frequency corresponding to the maximum sum of maximum AC power values ​​does not meet the requirements, then the target charge and discharge frequency corresponding to the maximum sum of maximum AC power output by each drive unit that meets the NVH requirements must be selected as the frequency reference value. That is, the frequency reference value must meet the requirement that the vibration and noise index of each drive unit corresponding to the frequency reference value is less than a preset threshold. After obtaining the frequency reference value, the frequency adjustment modules of the front drive and rear drive can adjust the rising slope k of the AC power of the corresponding drive unit. For example, this can be achieved in software by chopping the bus voltage of the multi-drive unit's power battery, or in hardware by changing the resistance of the series inductor. This changes the charging and discharging frequency to match the frequency reference value. Alternatively, the frequency adjustment modules of the front drive and rear drive can adjust the peak value of the AC power to change I. max To ensure the charging and discharging frequency matches the frequency reference value, the frequency adjustment modules of the front drive and rear drive can be adjusted by adding a period of zero AC power, i.e., changing the current freewheeling time, thereby changing T0, and ultimately adjusting the charging and discharging frequency to match the frequency reference value. When the frequencies of both the front drive and rear drive are consistent with the frequency reference value, the phase of each drive unit can be adjusted accordingly to match the phase reference value.

[0084] It should be noted that phase adjustment and frequency adjustment are not directly related, therefore, there is no specific order in the adjustment process. Furthermore, the charging and discharging frequency of the drive unit can be changed by adjusting two or three of the following: the rising slope of the AC power of each drive unit, the peak value of the AC power of the drive unit, and the time when the AC power of the drive unit is zero. This can improve working efficiency and increase the accuracy of the adjustment.

[0085] With the above settings, the charging and discharging frequency can be changed by various methods such as altering the rising slope of the AC power of each driving unit, the peak value of the AC power of the driving unit, or the time when the AC power of the driving unit is zero, thereby improving the operability and feasibility of the power battery heating method of the present invention.

[0086] Understandably, for multi-drive unit heating schemes, the order of frequency or phase adjustment does not need to be specified. However, in order to improve work efficiency and reduce errors, the working order of each drive unit, as well as the order of frequency and phase adjustment, can be set in advance so that orderly adjustment can be performed.

[0087] In one embodiment of the present invention, the step of obtaining the AC phase of the bus current of any one of the driving units and determining the obtained AC phase of the bus current as a phase reference value specifically includes:

[0088] One of the plurality of driving units is designated as the master driving unit, and the remaining driving units are designated as slave driving units. The phase of the master driving unit is obtained and set as the phase reference value.

[0089] In this embodiment, based on the above embodiments, a dual-drive electric vehicle is used as an example. The rear-drive unit is set as the primary drive unit, and the front-drive unit as the secondary drive unit. First, the maximum AC power output by the front and rear drives at different target charge / discharge frequencies and the corresponding vibration and noise indicators are calculated. The target charge / discharge frequency corresponding to the condition that the vibration and noise indicators are less than a preset threshold and the sum of the maximum AC power outputs of all drive units is the maximum value is determined as the frequency reference value. Then, with the primary drive unit as the main driver, the frequency of the rear drive is adjusted first. The rear drive begins charging / discharging and heating. The charging / discharging frequency of the rear drive is changed by adjusting one of the following: the rise slope of the rear drive's AC power, the peak value of the drive unit's AC power, or the time when the drive unit's AC power is zero, to make it consistent with the frequency reference value. When the charging / discharging frequency of the rear drive reaches the frequency reference value, the phase of the rear drive can be set as the phase reference value. Then, the phase of the front drive is adjusted to be consistent with the phase reference value. Thus, only the phase adjustment module of the front drive needs to be controlled to adjust the phase of the front drive; the phase of the rear drive does not need to be adjusted, improving the working efficiency of the power battery heating device.

[0090] It should be noted that, typically, the carrier frequency of a switching module is close to 10kHz, while the charging / discharging heating frequency is close to 2kHz. Therefore, shifting the frequency by one PWM carrier frequency cycle will result in a phase error of approximately 72°. This means that adjusting the phase by shifting the frequency by several PWM carrier frequency cycles while keeping the carrier frequency constant will result in a very large phase interval, which cannot meet the phase adjustment requirements of multiple drive units. Figure 9 As shown. Therefore, the power battery heating method of the present invention inserts a desired time period into the PWM control signal of the target controlled object during the phase adjustment process by inserting a transition carrier frequency period, thereby adjusting the AC phase of the bus current of the target controlled object so that the AC phase of the bus current of the target controlled object is consistent with the phase reference value.

[0091] As can be understood, taking the main controller as an example, the control chip can send a carrier-modulated PWM control signal to the inverter's driver chip. This carrier wave is implemented internally by a timer within the control chip. Typically, the PWM module is encapsulated as a peripheral of the control chip, allowing direct manipulation of the control chip's registers to change the waveform of the PWM control signal. For instance, the PWM carrier frequency can be changed by modifying the register value for the PWM period in the control chip.

[0092] Therefore, in one embodiment of the present invention, reference is made to Figure 6 and Figure 10 The step of inserting a transition carrier frequency period into the PWM control signal of the target controlled object to adjust the AC phase of the bus current of the target controlled object so that the AC phase of the bus current of the target controlled object is consistent with the phase reference value specifically includes:

[0093] Step S410: Obtain the initial period and initial carrier frequency from the PWM control signal of the target controlled object;

[0094] Step S420: Determine the carrier frequency of the transition carrier frequency period based on the phase reference value, the AC phase of the bus current of the target controlled object, and the frequency reference value;

[0095] Step S430: Determine the transition carrier frequency period of the target controlled object based on the initial period, the initial carrier frequency, and the carrier frequency of the transition carrier frequency period;

[0096] Step S440: Control the target control object to turn on in order to heat the battery, and when the heating time of the target control object is one initial cycle, use the transition carrier frequency period as the period of the PWM control signal of the target control object;

[0097] Step S450: Re-enable the target control object to heat the battery, and use the initial period as the period of the PWM control signal of the target control object when the heating duration of the target control object is one transition carrier frequency cycle.

[0098] Specifically, in the initial state without the insertion of a transition carrier frequency period, assuming the PWM period register value in the control chip is Reg_P0, and the corresponding PWM carrier frequency is fc0; therefore, the main controller of the target controlled object can obtain the initial period and the initial carrier frequency fc0 in the PWM control signal through the PWM period register value of Reg_P0; then, it obtains the AC phase change Δθ of the desired bus current, that is, the deviation Δθ between the AC phase of the actual bus current of the target controlled object and the phase reference value. Then, the insertion time should be: Δt=Δθ / 2πf ref Then, the carrier frequency of the corresponding transition period is calculated as f.ref =1 / Δt=2πf ref / △θ; Heat the target controlled object's battery, and after one charge-discharge heating cycle, pause the heating and change the PWM cycle register value of the control chip to Reg_P1, where: Reg_P1=Reg_P0*fc1 / fc0; Then continue heating the target controlled object, and after one transition carrier frequency cycle, change the PWM cycle register value of the control chip to Reg_P0. Subsequently, the target controlled object can continue to be charged and discharged for heating. At this time, the AC phase of the bus current of the target controlled object is consistent with the phase reference value.

[0099] By employing the above settings, the AC phase of the target object's bus current is adjusted by inserting a transitional carrier frequency cycle into the PWM control signal of the target object, thereby achieving the purpose of adjusting the AC phase of the bus current of each drive unit. Compared to the method of adjusting the phase by staggering several PWM carrier frequency cycles while keeping the carrier frequency constant, this method can meet the phase adjustment requirements of multi-drive unit power batteries, improving the feasibility and ease of operation of the power battery heating method of this invention.

[0100] In one embodiment of the present invention, reference is made to... Figure 5 The step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes:

[0101] Step S331: Select one of the multiple drive units as the target control object;

[0102] Step S332: Obtain the phase reference value and timestamp of the main drive unit at a preset time;

[0103] Step S333: Determine the desired phase change of the target controlled object based on the phase reference value and timestamp of the main drive unit at a preset time, and the AC phase and timestamp of the bus current of the target controlled object at a preset time.

[0104] Step S334: Adjust the AC phase of the bus current of the target controlled object according to the phase change until the AC phase of the adjusted bus current of the target controlled object is consistent with the phase reference value. Then return to the step of selecting one of the multiple slave drive units as the target controlled object until all the slave drive units have been selected.

[0105] Specifically, a transition carrier frequency period is inserted into the control signal of the target controlled object to adjust the AC phase of the bus current of the target controlled object, so that the AC phase of the bus current of the target controlled object is consistent with the phase reference value.

[0106] In this embodiment, since the main controllers of each drive unit are independent, it is necessary to achieve time synchronization among the drive units. For example, timestamps can be transmitted via a bus to achieve time synchronization among the drive units. Specifically, the main drive unit transmits its current timestamp T1 and current phase θ1 to the slave drive unit. The slave drive unit's phase reference value calculation module then combines this with its own current timestamp T1. n To calculate the expected phase change θ at the current moment n , where θ n =θ1+2πf ref ×(T n -T1). Thus, the phase reference value calculation module of each drive unit calculates the time to be inserted based on the expected phase change at the current moment, and then calculates the carrier frequency of the transition period. Then, the phase adjustment module adjusts the phase of its own drive unit to be consistent with the phase reference value by inserting the transition carrier frequency period.

[0107] Specifically, taking a distributed drive vehicle as an example, each of the four wheels has a motor and electronic control unit, denoted as left rear-wheel drive, right rear-wheel drive, left front-wheel drive, and right front-wheel drive, respectively. Therefore, it belongs to a four-drive unit. If each uses a three-phase four-arm switch module, there are no NVH issues during charging, discharging, and heating, so vibration and noise indicators do not need to be considered. The frequency reference value calculation module of each of the four drive units calculates the maximum AC power output and corresponding vibration and noise indicators at different target charging and discharging frequencies. Then, the maximum value among the sums of the maximum AC power is obtained. The target charging and discharging frequency corresponding to the condition that the vibration and noise indicators are less than a preset threshold and the sum of the maximum AC power is the maximum value is used as the frequency reference value. For example, if the left rear-wheel drive is the main drive unit, and the right rear-wheel drive, left front-wheel drive, and right front-wheel drive are all slave drive units, then the left rear-wheel drive can be charged, discharged, and heated first. During the charging, discharging, and heating process, at least one of the following can be adjusted: the rising slope of the left rear-wheel drive's AC power, the peak value of the drive unit's AC power, and the time when the drive unit's AC power is zero, to change the charging and discharging frequency of the left rear-wheel drive, so that the charging and discharging frequency of the left rear-wheel drive is consistent with the frequency reference value. After the heating frequency of the left rear drive reaches the frequency reference value, the frequency of other drive units can be adjusted according to a preset adjustment sequence. For example, the preset adjustment sequence is right rear drive, left front drive, right front drive. That is, the charging and discharging heating of the right rear drive is started first. At least one of the following is adjusted: the rising slope of the AC power of the right rear drive, the peak value of the AC power of the drive unit, and the time when the AC power of the drive unit is zero, to change the charging and discharging frequency of the right rear drive so that it is consistent with the frequency reference value. It can be understood that when the charging and discharging frequency of the left rear drive reaches the frequency reference value, the current phase and timestamp are transmitted to the right rear drive through the bus so that the phase reference value calculation module of the right rear drive can calculate the expected phase change at the current moment, calculate the time to be inserted, and then calculate the carrier frequency of the transition period. Then, the phase adjustment module adjusts the phase of its own drive unit to be consistent with the phase of the left rear drive by inserting the transition carrier frequency period. Then, the charging and discharging heating of the left front drive is started. At least one of the following is adjusted: the rising slope of the AC power of the left front drive, the peak value of the AC power of the drive unit, and the time when the AC power of the drive unit is zero, to change the charging and discharging frequency of the left front drive so that its charging and discharging frequency is consistent with the frequency reference value. When the charging and discharging frequency of the right rear drive reaches the frequency reference value, the current phase and timestamp are transmitted to the left front drive through the bus so that the phase reference value calculation module of the left front drive can calculate the expected phase change at the current moment, calculate the time to be inserted, and then calculate the carrier frequency of the transition period. Then, the phase adjustment module adjusts the phase of its own drive unit to be consistent with the phase of the right rear drive by inserting the transition carrier frequency period.Similarly, by activating the charging and discharging heating of the right front drive unit, the charging and discharging frequency of the right front drive unit is changed by adjusting at least one of the following: the rising slope of the AC power of the right front drive unit, the peak value of the AC power of the drive unit, and the time when the AC power of the drive unit is zero. Then, the phase and timestamp transmitted by the left front drive unit via the bus are received. The phase adjustment module of the right front drive unit then adjusts its own phase to match the phase of the left front drive unit by inserting a transition carrier frequency cycle. It should be noted that the preset adjustment sequence is set in advance by the R&D personnel. In this way, the frequency and phase of all four drive units are consistent, thereby ensuring the maximum sum of the AC power of each drive unit, i.e., maximizing the heating power of the multi-drive unit power battery, and improving the heating efficiency of the multi-drive unit power battery.

[0108] It is understandable that if the AC phase of the bus current of each drive unit is consistent, the total output current amplitude of the battery will be the largest. That is, it is possible to determine whether the AC phase of the bus current of the drive unit is consistent with that of the main drive unit by detecting the AC current amplitude of the battery.

[0109] Therefore, in another embodiment of the invention, reference is made to... Figure 3 The step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes:

[0110] Step S311: Select one of the multiple drive units as the target control object;

[0111] Step S312: Control the selected target control object to turn on in order to heat the battery, and turn off the battery heating function of other drive units.

[0112] Step S313: Adjust the AC phase of the bus current of the target controlled object until the output current of the multi-drive unit power battery is at its maximum value, then return to the step of selecting one of the multiple slave drive units as the target controlled object, until all the slave drive units have been selected.

[0113] Based on the above embodiments, taking the left rear drive as the main drive unit in a four-drive unit as an example, the charging and discharging frequencies of each drive unit can be adjusted first to ensure they are consistent with the frequency reference value. Then, any one of the drive units can be selected as the target control object, and its battery heating function can be activated. For example, if the left front drive is selected, its battery heating function is activated, while the battery heating functions of the right rear drive and right front drive are deactivated. Then, the AC phase of the bus current of the left front drive is adjusted by inserting a transition carrier frequency cycle until the output current of the multi-drive unit's power battery reaches its maximum value, i.e., the operating current of the multiple drive units. When the total sum reaches its maximum value, i.e., when the total battery AC current is at its maximum, phase adjustment for the left front drive is stopped, and the phase of the left front drive is fixed at this phase. Similarly, the battery heating function of the right rear drive is activated, while the battery heating functions of other slave drive units are deactivated. Then, the AC phase of the bus current of the right rear drive is adjusted by inserting a transition carrier frequency cycle until the sum of the operating currents of multiple drive units reaches its maximum value, i.e., when the total battery AC current is at its maximum, phase adjustment for the right rear drive is stopped, and the phase of the right rear drive is fixed at this phase. The next step is to use the right front drive as the target control object for phase adjustment until all the slave drive units are selected, i.e., to achieve phase consistency of the four drive units. It should be noted that the activation order of each drive unit can be set in advance by the R&D personnel. In addition, a current detection circuit can be set in the power battery heating device, such as a shunt to detect the total current of the power battery, or when the total battery AC current is at its maximum, the power battery heating device can receive feedback signals from the vehicle controller or BMS battery management system, etc., to know that the sum of the current of the current battery is at its maximum, and the phase at this time needs to be fixed to be consistent with the phase reference value. In this way, when all driving units have the same frequency, the phase of each slave driving unit is kept consistent with that of the master driving unit, thus improving the heating efficiency of the battery.

[0114] It is understandable that the greater the AC power on the battery bus, the greater the amplitude of the bus voltage fluctuation. Therefore, the AC phase of the bus current from the drive unit can be determined by detecting the amplitude of the bus voltage fluctuation.

[0115] In one embodiment of the present invention, reference is made to Figure 4 The step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes:

[0116] Step S321: Select one of the multiple drive units as the target control object;

[0117] Step S322: Control the selected target control object to turn on in order to heat the battery, and turn off the battery heating function of other drive units.

[0118] Step S323: Adjust the AC phase of the bus current of the target controlled object until the fluctuation amplitude of the bus voltage of the selected target controlled object is at its maximum value, then return to the step of selecting one of the multiple slave drive units as the target controlled object, until all the slave drive units have been selected.

[0119] In this embodiment, a four-drive unit is used as an example. Based on the above embodiments, the charging and discharging frequencies of each drive unit are adjusted to ensure they match the frequency reference value. Then, any one of the drive units is selected as the target control object, and its battery heating function is activated. For example, if the left front drive is selected, its battery heating function is activated, while the right rear drive and right front drive batteries are deactivated. Then, the AC phase of the left front drive bus current is adjusted by inserting a transition carrier frequency cycle until the fluctuation amplitude of the target control object's bus voltage reaches its maximum value, i.e., the bus voltage fluctuation detected by the left front drive. When the amplitude fluctuation is at its maximum, phase adjustment of the left front drive is stopped, and the phase of the left front drive is fixed at that phase. Similarly, the battery heating function of the right rear drive is turned on, and the battery heating function of other slave drive units is turned off. Then, the AC phase of the bus current of the right rear drive is adjusted by inserting a transition carrier frequency cycle until the fluctuation amplitude of the bus voltage of the target controlled object is at its maximum value, that is, when the bus voltage fluctuation amplitude detected by the right rear drive is at its maximum, phase adjustment of the right rear drive is stopped, and the phase of the right rear drive is fixed at that phase. The next step is to use the right front drive as the target controlled object for phase adjustment until all the slave drive units are selected, that is, to achieve phase consistency of the four drive units. It should be noted that the turn-on order of each drive unit can be arbitrarily selected. It should also be noted that the main controller in each drive unit can be set to detect the detection circuit for its own bus voltage. When it is the target controlled object, it outputs a corresponding detection signal when it detects that its own bus voltage fluctuation amplitude is at its maximum, so that the phase adjustment module of the target controlled object stops working and the AC phase of the target object's bus current is fixed to be consistent with the phase reference value. In addition, the main controller can also receive feedback signals from the vehicle controller or BMS battery management system, thereby knowing that the current bus voltage fluctuation amplitude is the largest and that the phase at this time needs to be fixed to keep in line with the phase reference value.

[0120] The above settings enable phase adjustment of multiple drive units to ensure that the AC phase of the bus current of each drive unit in the multi-drive unit power battery is consistent, so as to achieve better heating efficiency when the charging and discharging frequencies of each drive unit are consistent.

[0121] The present invention also proposes a power battery heating device, comprising:

[0122] Memory;

[0123] Processor; and

[0124] A power battery heating control program stored in a memory and executable on a processor, wherein the processor executes the power battery heating control program to implement the power battery heating method described above.

[0125] It is worth noting that since the power battery heating device of the present invention is based on the above-described power battery heating method, the embodiments of the power battery heating device of the present invention include all the technical solutions of all embodiments of the above-described power battery heating method, and the technical effects achieved are exactly the same, so they will not be repeated here.

[0126] The present invention also proposes an electric vehicle, including a multi-drive unit power battery and the control device described in the above embodiments.

[0127] It is worth noting that since the electric vehicle of the present invention is based on the above-mentioned power battery heating device, the embodiments of the electric vehicle of the present invention include all the technical solutions of all embodiments of the above-mentioned power battery heating device, and the technical effects achieved are exactly the same, so they will not be repeated here.

[0128] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for heating a power battery, applied to an electric vehicle with multiple drive units, characterized in that, The power battery heating method includes: The maximum AC power output by each drive unit at different target charging and discharging frequencies and the corresponding vibration and noise indicators are obtained. The target charging and discharging frequency that meets the condition that the vibration and noise indicators are less than a preset threshold and the sum of the maximum AC power output by each drive unit is the maximum value is determined as the frequency reference value. The AC phase of the bus current of any one of the drive units is obtained, and the obtained AC phase of the bus current is determined as the phase reference value. The charging and discharging frequencies of each driving unit are adjusted according to the frequency reference value so that the charging and discharging frequencies of each driving unit are consistent with the frequency reference value; and The AC phase of the bus current of each drive unit is adjusted according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value. The step of obtaining the AC phase of the bus current of any one of the driving units and determining the obtained AC phase of the bus current as a phase reference value specifically includes: One of the plurality of driving units is designated as the master driving unit, and the remaining driving units are designated as slave driving units. The phase of the master driving unit is obtained and set as the phase reference value. Select one of the multiple drive units as the target control object; A transition carrier frequency period is inserted into the PWM control signal of the target controlled object to adjust the AC phase of the bus current of the target controlled object so that the AC phase of the bus current of the target controlled object is consistent with the phase reference value.

2. The power battery heating method as described in claim 1, characterized in that, The step of adjusting the charging and discharging frequency of each driving unit according to the frequency reference value, so that the charging and discharging frequency of each driving unit is consistent with the frequency reference value, includes: The charging and discharging frequency of each driving unit is adjusted according to the frequency reference value, including the rising slope of the AC power of each driving unit, the peak value of the AC power of the driving unit, and the time when the AC power of the driving unit is zero, so that the charging and discharging frequency of each driving unit is consistent with the frequency reference value.

3. The power battery heating method as described in claim 1, characterized in that, The step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes: Select one of the multiple drive units as the target control object; The selected target control object is turned on to heat the battery, while the battery heating function of other drive units is turned off. Adjust the AC phase of the bus current of the target controlled object until the output current of the multi-drive unit power battery is at its maximum value, then return to the step of selecting one of the multiple slave drive units as the target controlled object, until all the slave drive units have been selected.

4. The power battery heating method as described in claim 1, characterized in that, The step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes: Select one of the multiple drive units as the target control object; The selected target control object is turned on to heat the battery, while the battery heating function of other drive units is turned off. Adjust the AC phase of the bus current of the target controlled object until the fluctuation amplitude of the bus voltage of the selected target controlled object is at its maximum value, then return to the step of selecting one of the multiple slave drive units as the target controlled object, until all the slave drive units have been selected.

5. The power battery heating method as described in claim 1, characterized in that, The step of adjusting the AC phase of the bus current of each drive unit according to the phase reference value so that the AC phase of the bus current of each drive unit is consistent with the phase reference value specifically includes: Select one of the multiple drive units as the target control object; Obtain the phase reference value and timestamp of the main drive unit at a preset time; The desired phase change of the target controlled object is determined based on the phase reference value and timestamp of the main drive unit at a preset time, and the AC phase and timestamp of the bus current of the target controlled object at a preset time. Adjust the AC phase of the bus current of the target controlled object according to the phase change until the AC phase of the adjusted bus current of the target controlled object is consistent with the phase reference value. Then, return to the step of selecting one of the multiple slave drive units as the target controlled object until all the slave drive units have been selected.

6. The power battery heating method as described in claim 1, characterized in that, The step of inserting a transition carrier frequency period into the PWM control signal of the target controlled object to adjust the AC phase of the bus current of the target controlled object so that the AC phase of the bus current of the target controlled object is consistent with the phase reference value specifically includes: Obtain the initial period and initial carrier frequency from the PWM control signal of the target controlled object; The carrier frequency of the transition carrier frequency period is determined based on the phase reference value, the AC phase of the bus current of the target controlled object, and the frequency reference value. The transition carrier frequency period of the target controlled object is determined based on the initial period, the initial carrier frequency, and the carrier frequency of the transition carrier frequency period. The target control object is turned on to heat the battery, and the transition carrier frequency period is used as the period of the PWM control signal of the target control object when the heating time of the target control object is one initial cycle. Re-enable the target control object to heat the battery, and use the initial period as the period of the PWM control signal of the target control object when the heating duration of the target control object is one transition carrier frequency cycle.

7. A power battery heating device, characterized in that, The power battery heating device includes: Memory; Processor; and A power battery heating control program stored in a memory and executable on a processor, wherein the processor, when executing the power battery heating control program, implements the power battery heating method as described in any one of claims 1-6.

8. An electric vehicle, characterized in that, The electric vehicle includes a multi-drive unit power battery and a power battery heating device as described in claim 7.

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