CN117719394A - Power battery heating method and system and vehicle electric drive device - Google Patents

Abstract

The invention provides a power battery heating method and system and a vehicle electric drive device, wherein the method comprises the following steps: correcting the d-axis voltage amplitude limit value corresponding to the d-axis voltage amplitude limit value initial instruction according to the heating environment of the power battery to obtain a d-axis voltage amplitude correction limit value; correcting the d-axis current limit value corresponding to the d-axis current limit value initial instruction to obtain a d-axis current correction limit value; carrying out current prediction on the d axis to obtain a d axis current predicted value; obtaining a real-time instruction of the d-axis voltage amplitude limit value through the d-axis voltage amplitude correction limit value, the d-axis current correction limit value and the d-axis current predicted value; based on the d-axis voltage amplitude limit real-time instruction, positive and negative abrupt change voltage is provided for the d axis, and pulse current is generated by using the d-axis inductor, so that the power battery is heated according to the pulse current. The invention can periodically charge and discharge the power battery by generating the pulse current, thereby heating the power battery.

Description

Power battery heating method and system and vehicle electric drive device

Technical Field

The invention relates to the technical field of batteries, in particular to a power battery heating method and system and a vehicle electric drive device.

Background

At present, a new energy automobile mostly adopts a power lithium battery as an energy storage device, the performance of the power lithium battery is greatly affected by temperature, the performance of the power lithium battery can be greatly deteriorated in a low-temperature environment, and the discharging capability is reduced, so that a scheme for heating the power lithium battery is needed.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a power battery heating method and system, and a vehicle electric driving device, which are used for solving the problem of how to quickly heat a power battery.

To achieve the above and other related objects, the present invention provides a power battery heating method, comprising the steps of:

acquiring a motor direct-axis voltage amplitude limit value initial instruction and a motor direct-axis current limit value initial instruction which are generated in advance or in real time;

correcting the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery to obtain a motor direct-axis voltage amplitude correction limit value; correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value;

Current prediction is carried out on the motor straight shaft to obtain a motor straight shaft current prediction value;

the initial command of the motor direct-axis voltage amplitude value is adjusted through the motor direct-axis voltage amplitude value correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current predicted value, so that a real-time command of the motor direct-axis voltage amplitude value is obtained;

based on the real-time instruction of the amplitude limit value of the motor direct-axis voltage, positive and negative abrupt change voltage is provided for the motor direct-axis, and pulse current is generated by utilizing the motor direct-axis inductance so as to heat the power battery according to the pulse current.

In an embodiment of the present invention, a process for predicting a current of a motor straight shaft to obtain a predicted value of the current of the motor straight shaft includes:

acquiring a motor direct-axis inductance value and a motor direct-axis voltage amplitude value of a current power battery heating period;

inputting the motor direct-axis inductance value and the motor direct-axis voltage amplitude value of the current power battery heating period into a current calculation equation, and predicting the motor direct-axis current variation of the next power battery heating period and the motor direct-axis current value of the next power battery heating period; wherein the current calculation equation includes:wherein Ud represents the motor direct-axis voltage amplitude value, L of the current power battery heating period _d Represents the direct axis inductance value of the motor, < >>The direct-axis current variation of the motor is shown, and t is the time of the heating cycle of the power battery.

In an embodiment of the present invention, a process for predicting a current of a motor straight shaft to obtain a predicted value of the current of the motor straight shaft includes:

and calculating a current difference value between the motor straight-axis current value of the current power battery heating period and the motor straight-axis current value of the previous power battery heating period, and predicting the motor straight-axis current value of the next power battery heating period based on the current difference value.

In an embodiment of the present invention, after obtaining the predicted value of the direct current of the motor, the method further includes:

comparing a motor direct-axis current predicted value with a motor direct-axis current limit value corresponding to the motor direct-axis current limit value initial instruction, and reversing a motor direct-axis voltage amplitude limit value corresponding to the motor direct-axis voltage amplitude limit value initial instruction when the motor direct-axis current predicted value is larger than the motor direct-axis current limit value, so as to carry out overcurrent protection on the motor through the reverse action of voltage;

or comparing the motor direct-axis current predicted value with the motor direct-axis current correction limit value, and reversing the motor direct-axis voltage amplitude correction limit value when the motor direct-axis current predicted value is larger than the motor direct-axis current correction limit value so as to carry out overcurrent protection on the motor through the reverse action of voltage.

In an embodiment of the present invention, based on the real-time command of the voltage amplitude limit value of the motor direct axis, the process of providing the positive and negative abrupt voltage to the motor direct axis includes:

responding to the real-time instruction of the amplitude limit value of the motor direct-axis voltage, and acquiring a motor torque equation;

and based on the motor torque equation, after the motor quadrature current and the motor quadrature voltage are controlled to be zero, positive and negative abrupt change voltages are provided for the motor direct axis.

In an embodiment of the present invention, when a positive and negative abrupt voltage is provided to a motor straight shaft, a waveform of the voltage includes: square wave, sine wave, triangular wave or trapezoidal wave.

In an embodiment of the present invention, before acquiring the initial command of the motor direct-axis voltage amplitude limit value and the initial command of the motor direct-axis current limit value, which are generated in advance or in real time, the method further includes:

detecting whether the motor has a fault or not, and detecting whether a motor controller has a fault or not;

if the motor has no fault, the motor controller normally receives a power battery heating instruction sent from the outside, and if the motor controller has no fault, a motor direct-axis voltage amplitude limit value initial instruction and a motor direct-axis current limit value initial instruction which are generated in advance or in real time are obtained;

If the motor fails, the motor controller can not normally receive the power battery heating command sent from the outside, and/or if the motor controller fails, the motor controller stops acquiring the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command which are generated in advance or in real time.

In an embodiment of the present invention, the generating process of the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command includes:

and generating the initial command of the amplitude limit value of the motor direct-axis voltage and the initial command of the current limit value of the motor direct-axis in advance or in real time according to the state of the motor, the state of the motor controller and the state of the power battery.

The invention also provides a power battery heating system, which comprises:

the initial command module is used for acquiring a motor direct-axis voltage amplitude limit value initial command and a motor direct-axis current limit value initial command which are generated in advance or in real time;

the correction module is used for correcting the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery to obtain a motor direct-axis voltage amplitude correction limit value; correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value;

The current prediction module is used for predicting the current of the motor straight shaft to obtain a motor straight shaft current predicted value;

the command adjustment module is used for adjusting the initial command of the motor direct-axis voltage amplitude limit value through the motor direct-axis voltage amplitude correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current predicted value to obtain a real-time command of the motor direct-axis voltage amplitude limit value;

and the power battery heating module is used for providing positive and negative abrupt change voltage for the motor direct shaft according to the real-time instruction of the voltage amplitude limit value of the motor direct shaft, and generating pulse current by utilizing the inductance of the motor direct shaft so as to heat the power battery according to the pulse current.

The invention also provides a vehicle electric drive apparatus for performing the power battery heating method as set forth in any one of the above.

As described above, the invention provides a power battery heating method and system, and a vehicle electric drive device, which have the following beneficial effects: the method comprises the steps of obtaining a motor direct-axis voltage amplitude limit value initial instruction and a motor direct-axis current limit value initial instruction which are generated in advance or in real time; then, correcting the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery to obtain a motor direct-axis voltage amplitude correction limit value; correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value; carrying out current prediction on the motor straight shaft to obtain a motor straight shaft current prediction value; the initial command of the motor direct-axis voltage amplitude limit value is adjusted through the motor direct-axis voltage amplitude correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current predicted value, so that the real-time command of the motor direct-axis voltage amplitude limit value is obtained; and finally, providing positive and negative abrupt change voltage for the motor direct shaft based on the real-time instruction of the motor direct shaft voltage amplitude limit value, and generating pulse current by utilizing the motor direct shaft inductance so as to heat the power battery according to the pulse current. Therefore, the invention can periodically charge and discharge the power battery by generating pulse current, thereby heating the power battery. In addition, the motor is protected by combining the motor direct-axis current predicted value to adjust and generate the motor direct-axis voltage amplitude limit value real-time instruction, so that the motor is prevented from being failed due to transient overcurrent of the real-time current of the motor direct axis. In addition, before positive and negative abrupt change voltage is provided for the motor direct shaft, the motor cross shaft current and the motor cross shaft voltage can be controlled to be zero according to a motor torque equation, so that motor torque is avoided, and damage to power devices in a motor controller is reduced.

Drawings

FIG. 1 is a flow chart of a power battery heating method according to an embodiment of the invention;

FIG. 2 is a schematic diagram showing a relationship between temperature and time when a power battery is heated according to an embodiment of the present invention;

FIG. 3 is a schematic flow chart of a method for heating a power battery according to another embodiment of the present invention;

FIG. 4 is a schematic diagram of circuit connection for heating a power battery according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a motor direct-axis voltage waveform according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a circuit connection of a power battery according to an embodiment of the present invention when discharging;

FIG. 7 is a schematic diagram of circuit connection for charging a power battery according to an embodiment of the present invention;

fig. 8 is a schematic hardware structure of a power battery heating system according to an embodiment of the invention.

Detailed Description

Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.

It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.

The existing power battery heating technology mainly utilizes cooling liquid heated by other devices (such as PTC thermistors, electric drive systems and the like) to heat the battery through a whole vehicle thermal management system, and the disadvantage of indirect heating is that the heating speed is not high. In addition, there are schemes in which a pulse current is directly generated by an electric drive system to heat, which generates a pulse current by using a motor inductance and then generates heat by using a battery internal resistance. However, this solution has common problems of easily triggering an electric drive system to overcurrent, overheat, generate torque, generate noise, and the like. While there are currently some drawbacks to optimizing by modifying the modulation algorithm, such as freewheeling the current back into the power cell by turning off the power device; however, the corresponding optimization process is easy to damage the inverter power device, especially the SiC MOS power module, because the body diode has large internal resistance and small overcurrent capability when the SiC device freewheels, and is easy to generate heat and damage. In addition, by modifying the scheme of the modulation algorithm, the software is greatly changed, algorithms such as SVPWM (Space Vector Pulse Width Modulation, space vector pulse width modulation, SVPWM for short) and the like commonly used for motor control cannot be multiplexed, development complexity is increased, and functional stability is reduced. In view of the above problems or drawbacks, the present embodiments provide a power battery heating method and system to solve the above problems or drawbacks.

Specifically, in an exemplary embodiment, fig. 1 shows a schematic flow chart of a power battery heating method according to an embodiment of the present invention. As shown in fig. 1, this embodiment provides a power battery heating method including the steps of:

s110, acquiring a motor direct-axis voltage amplitude limit value initial command and a motor direct-axis current limit value initial command which are generated in advance or in real time. As an example, in the present embodiment, the generation process of the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command includes: and generating an initial command of the motor direct-axis voltage amplitude limit value and an initial command of the motor direct-axis current limit value in advance or in real time according to the state of the motor, the state of the motor controller and the state of the power battery. Specifically, the initial command of the motor direct-axis voltage amplitude limit value and the initial command of the motor direct-axis current limit value can be generated by adopting preset values, and can also be generated according to the state of a three-electric system; for example, setting a motor direct-axis voltage amplitude limit value according to the magnitude of the bus voltage, and then generating a corresponding instruction to obtain an initial instruction of the motor direct-axis voltage amplitude limit value. In this embodiment, the three-electric system includes, but is not limited to, a motor controller, and a power battery in the new energy vehicle. In this or other embodiments, the motor direct axis may also be referred to as the d-axis, and the motor quadrature axis may be referred to as the q-axis; the motor may be configured or referred to as an electric drive, and the motor controller may also be configured by an inverter.

S120, correcting the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery to obtain a motor direct-axis voltage amplitude correction limit value; and correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value. As an example, in the present embodiment, the power cell heating environment includes, but is not limited to: external water temperature, external voltage, motor controller temperature, motor controller voltage, power battery temperature, power battery voltage, stator temperature in the motor, rotor temperature in the motor, inverter power device temperature in the motor controller, and the like.

S130, current prediction is carried out on the motor straight shaft, and a motor straight shaft current predicted value is obtained;

s140, adjusting an initial command of the motor direct-axis voltage amplitude limit value through the motor direct-axis voltage amplitude correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current predicted value to obtain a real-time command of the motor direct-axis voltage amplitude limit value;

and S150, providing positive and negative abrupt voltage for the motor direct shaft based on the real-time instruction of the motor direct shaft voltage amplitude limit value, and generating pulse current by utilizing the motor direct shaft inductance so as to heat the power battery according to the pulse current. As an example, when the present embodiment provides positive and negative abrupt voltages to the motor direct shaft, waveforms of the voltages include, but are not limited to: square wave, sine wave, triangular wave or trapezoidal wave.

It is understood that the present embodiment can periodically charge and discharge the power battery by generating the pulse current, thereby heating the power battery. In addition, the motor can be protected by combining the motor direct-axis current predicted value to adjust and generate the motor direct-axis voltage amplitude limit value real-time instruction, and the motor is prevented from being failed due to transient overcurrent of the real-time current of the motor direct axis. In addition, before the positive and negative abrupt change voltage is provided for the motor direct axis, the motor cross axis current and the motor cross axis voltage can be controlled to be zero according to a motor torque equation, so that the motor torque is avoided, and the damage to power devices in a motor controller is reduced. The relationship between the temperature and time when the power battery is heated by the power battery heating scheme provided by the embodiment is shown in fig. 2. Therefore, the power battery heating scheme provided by the embodiment can enable the heating speed of the power battery to reach more than 2 cameras per minute. Compared with other existing heating schemes, the heating efficiency is improved, and the heating time is saved. In this embodiment, the circuit connection when the power battery is discharged is shown in fig. 6, and the circuit connection when the power battery is charged is shown in fig. 7.

In the heating process of the power battery, the motor winding resistance and the motor direct-axis inductance change due to the physical characteristics of motor temperature change, inductance saturation and the like, so that phase current transient overcurrent is caused, and therefore, the motor direct-axis current needs to be controlled to avoid overcurrent. Specifically, in an exemplary embodiment, the process of predicting the current of the motor direct shaft to obtain the predicted value of the current of the motor direct shaft may include: acquiring a motor direct-axis inductance value and a motor direct-axis voltage amplitude value of a current power battery heating period; inputting the motor direct-axis inductance value and the motor direct-axis voltage amplitude value of the current power battery heating period into a current calculation equation, and predicting the motor direct-axis current variation of the next power battery heating period and the motor direct-axis current value of the next power battery heating period; wherein the current calculation equation includes:wherein Ud represents the motor direct-axis voltage amplitude value, L of the current power battery heating period _d Represents the direct axis inductance value of the motor, < >>The direct-axis current variation of the motor is shown, and t is the time of the heating cycle of the power battery. In addition, after obtaining the predicted value of the motor direct-axis current, the embodiment may further include: and comparing the motor direct-axis current predicted value with a motor direct-axis current limit value corresponding to the motor direct-axis current limit value initial instruction, and reversing the motor direct-axis voltage amplitude limit value corresponding to the motor direct-axis voltage amplitude limit value initial instruction when the motor direct-axis current predicted value is larger than the motor direct-axis current limit value, so as to carry out overcurrent protection on the motor through the reverse action of voltage.

According to the above description, in another exemplary embodiment, the process of predicting the current of the motor direct shaft to obtain the predicted value of the current of the motor direct shaft according to the present embodiment may further include: and calculating a current difference value between the motor straight-axis current value of the current power battery heating period and the motor straight-axis current value of the previous power battery heating period, and predicting the motor straight-axis current value of the next power battery heating period based on the current difference value. In addition, after obtaining the predicted value of the motor direct-axis current, the embodiment may further include: and comparing the motor direct-axis current predicted value with a motor direct-axis current correction limit value, and reversing the motor direct-axis voltage amplitude correction limit value when the motor direct-axis current predicted value is larger than the motor direct-axis current correction limit value so as to carry out overcurrent protection on the motor through the reverse action of voltage.

Therefore, since the motor controller has time delay when generating the control voltage, the embodiment can predict the current of the motor direct shaft, then control the current according to the predicted current, and avoid the overcurrent of the motor direct shaft current, thereby protecting the motor.

In an exemplary embodiment, based on the motor direct-axis voltage amplitude limit real-time command, the process of providing positive and negative abrupt voltages to the motor direct-axis may include: responding to a real-time instruction of the amplitude limit value of the motor direct-axis voltage, and acquiring a motor torque equation; based on a motor torque equation, after motor quadrature current and motor quadrature voltage are controlled to be zero respectively, positive and negative abrupt change voltages are provided for a motor direct axis. As an example, when the present embodiment provides positive and negative abrupt voltages to the motor direct shaft, waveforms of the voltages include, but are not limited to: square wave, sine wave, triangular wave or trapezoidal wave. As an example, when the present embodiment heats the power battery according to the circuit connection shown in fig. 4, the motor is in a state of a lower three-pipe short circuit or an upper three-pipe short circuit, in which a current flows inside the motor without entering the battery, and therefore, the use of a voltage vector corresponding to the lower three-pipe short circuit or the upper three-pipe short circuit should be reduced as much as possible, and it is required that the effective value of the given motor straight-axis voltage amplitude Ud is as large as possible, so that the present embodiment can select a square wave as the most effective waveform corresponding to the straight-axis voltage command. In the circuit connection shown in fig. 4, the lower three transistors may be constituted by a mosfet U2, a mosfet V2, and a mosfet W2; the upper three transistors may be formed by a mosfet U1, a mosfet V1 and a mosfet W1. The voltage vector of the lower three-tube short circuit may be set to 000 and the voltage vector of the upper three-tube short circuit may be set to 111.

In an exemplary embodiment, before acquiring the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command, which are generated in advance or in real time, the embodiment may further include:

detecting whether the motor has a fault or not, and detecting whether a motor controller has a fault or not;

if the motor has no fault, the motor controller normally receives a power battery heating instruction sent from the outside, and if the motor controller has no fault inside, a motor straight shaft voltage amplitude limit value initial instruction and a motor straight shaft current limit value initial instruction which are generated in advance or in real time are obtained;

if the motor fails, the motor controller can not normally receive the power battery heating command sent from the outside and/or the motor controller fails, and the acquisition of the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command which are generated in advance or in real time is stopped.

It can be seen that, before the initial command of the motor direct-axis voltage amplitude limit value and the initial command of the motor direct-axis current limit value are generated, the embodiment can check whether the function can be normally started, and the starting conditions include but are not limited to: 1) Receiving an instruction of starting a function of an upper controller; 2) No fault exists in the motor controller; 3) No faults exist in the motor.

In another exemplary embodiment of the present invention, fig. 3 is a schematic flow chart of a power battery heating method according to an embodiment of the present invention. As shown in fig. 3, this embodiment provides a power battery heating method including the steps of:

step A is implemented: it is checked whether the function can be normally turned on, and the starting conditions include, but are not limited to: 1) Receiving an instruction of starting a function of an upper controller; 2) No fault exists in the motor controller; 3) No faults exist in the motor.

And (B) implementing the step (B): after the function is normally turned on, d-axis voltage amplitude limit and current limit commands need to be generated. According to the motor torque equation, if torque is to be avoided, the q-axis current needs to be controlled to 0, and therefore, the q-axis voltage should be given to 0, and the q-axis current is controlled to 0. Meanwhile, given positive and negative alternating d-axis voltage, alternating current is generated by using d-axis inductance of the motor, and as the d-axis voltage is always given by a modulation algorithm, the situation that six bridge arms are completely turned off does not exist, so that current cannot flow to a bus battery through a body diode, and a power module cannot be damaged. The d-axis voltage amplitude limit value and the current limit value command can be preset values, and can also be generated according to the state of a three-electric system, such as setting the d-axis voltage amplitude limit value according to the bus voltage. In this embodiment, the three-electric system includes, but is not limited to, a motor controller, and a power battery in the new energy vehicle.

And C, implementing the step: and adjusting the real-time d-axis voltage amplitude limit value instruction. In the motor control modulation algorithm, when the voltage vector is 000 or 111, the motor is in a state of a lower three-pipe short circuit or an upper three-pipe short circuit, and in this state, current flows inside the motor without entering the battery. Thus, the use of these two vectors should be reduced as much as possible, so the effective value of a given d-axis voltage amplitude Ud needs to be as large as possible, so the most effective waveform for the d-axis voltage amplitude limit command is a square wave. The waveform of the d-axis voltage amplitude Ud is shown in fig. 5. In the working process, the resistance of the motor winding and the d-axis inductance can be changed due to the physical characteristics of motor temperature change, inductance saturation and the like, so that phase current transient state overcurrent is caused. Therefore, it is necessary to control the d-axis current to avoid overcurrent. The d-axis current may be controlled by reversing the d-axis voltage amplitude limit command value when the d-axis current is detected to be excessively large, and the d-axis current may be rapidly reduced by the reverse action of the voltage.

And D, implementing the step: the d-axis voltage amplitude limit and the d-axis current limit can be corrected by integrating a plurality of factors. Due to changes in external conditions, such as changes in water temperature, changes in voltage, electrical drive system or battery system failures, such as over-temperature, or over-voltage failures, may be caused. Therefore, the d-axis voltage amplitude limit and the d-axis current monitoring threshold need to be integrated with each temperature information, and the voltage information is dynamically adjusted, including but not limited to water temperature, stator temperature, rotor temperature, power module temperature, etc.

And E, implementing the step: in order to achieve better current control effect, the d-axis current is predicted. Because the delay condition exists in the final generated control voltage is calculated, a current prediction module is needed to predict the d-axis current, and the prediction method can be as follows: predicting the current of the next period through the current difference value of the last two periods, and adopting a control strategy in advance. The prediction method may also be: by d-axis inductance value L in motor parameters calibrated in advance _d By means ofTo predict the current variation of the next cycle and the current value of the next cycle.

The relationship between the temperature and time when the power battery is heated by the power battery heating scheme provided by the embodiment is shown in fig. 2. Therefore, the power battery heating scheme provided by the embodiment can enable the heating speed of the power battery to reach more than 2 cameras per minute. Compared with other existing heating schemes, the heating efficiency is improved, and the heating time is saved. In this embodiment, the circuit connection when the power battery is discharged is shown in fig. 6, and the circuit connection when the power battery is charged is shown in fig. 7. It is understood that the present embodiment can periodically charge and discharge the power battery by generating the pulse current, thereby heating the power battery. In addition, the motor can be protected by combining the motor direct-axis current predicted value to adjust and generate the motor direct-axis voltage amplitude limit value real-time instruction, and the motor is prevented from being failed due to transient overcurrent of the real-time current of the motor direct axis. In addition, before the positive and negative abrupt change voltage is provided for the motor direct axis, the motor cross axis current and the motor cross axis voltage can be controlled to be zero according to a motor torque equation, so that the motor torque is avoided, and the damage to power devices in a motor controller is reduced.

In summary, the invention provides a power battery heating method, which comprises the steps of obtaining a motor direct-axis voltage amplitude limit value initial command and a motor direct-axis current limit value initial command which are generated in advance or in real time; then, correcting the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery to obtain a motor direct-axis voltage amplitude correction limit value; correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value; carrying out current prediction on the motor straight shaft to obtain a motor straight shaft current prediction value; the initial command of the motor direct-axis voltage amplitude limit value is adjusted through the motor direct-axis voltage amplitude correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current predicted value, so that the real-time command of the motor direct-axis voltage amplitude limit value is obtained; and finally, providing positive and negative abrupt change voltage for the motor direct shaft based on the real-time instruction of the motor direct shaft voltage amplitude limit value, and generating pulse current by utilizing the motor direct shaft inductance so as to heat the power battery according to the pulse current. It is known that the method can periodically charge and discharge the power battery by generating pulse current, thereby heating the power battery. In addition, the method generates the real-time command of the amplitude limit value of the motor direct-axis voltage by combining with the predicted value of the motor direct-axis current, so that the motor can be protected, and the motor is prevented from being failed due to transient overcurrent of the real-time current of the motor direct-axis. In addition, the method can control the motor cross current and the motor cross voltage to be zero according to a motor torque equation before providing positive and negative abrupt change voltage for the motor direct axis, thereby avoiding generating motor torque and reducing damage to power devices in a motor controller.

In another exemplary embodiment of the present invention, as shown in fig. 8, there is provided a power battery heating system including:

the initial command module 810 is configured to obtain a motor direct-axis voltage amplitude limit initial command and a motor direct-axis current limit initial command that are generated in advance or in real time. As an example, in the present embodiment, the generation process of the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command includes: and generating an initial command of the motor direct-axis voltage amplitude limit value and an initial command of the motor direct-axis current limit value in advance or in real time according to the state of the motor, the state of the motor controller and the state of the power battery. Specifically, the initial command of the motor direct-axis voltage amplitude limit value and the initial command of the motor direct-axis current limit value can be generated by adopting preset values, and can also be generated according to the state of a three-electric system; for example, setting a motor direct-axis voltage amplitude limit value according to the magnitude of the bus voltage, and then generating a corresponding instruction to obtain an initial instruction of the motor direct-axis voltage amplitude limit value. In this embodiment, the three-electric system includes, but is not limited to, a motor controller, and a power battery in the new energy vehicle. In this or other embodiments, the motor direct axis may also be referred to as the d-axis, and the motor quadrature axis may be referred to as the q-axis; the motor may be configured or referred to as an electric drive, and the motor controller may also be configured by an inverter.

The correction module 820 is configured to correct the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery, so as to obtain a motor direct-axis voltage amplitude correction limit value; and correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value. As an example, in the present embodiment, the power cell heating environment includes, but is not limited to: external water temperature, external voltage, motor controller temperature, motor controller voltage, power battery temperature, power battery voltage, stator temperature in the motor, rotor temperature in the motor, inverter power device temperature in the motor controller, and the like.

The current prediction module 830 is configured to perform current prediction on the motor direct axis to obtain a current prediction value of the motor direct axis;

the instruction adjusting module 840 is configured to adjust the initial instruction of the motor direct-axis voltage amplitude limit value by using the motor direct-axis voltage amplitude correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current prediction value, to obtain a real-time instruction of the motor direct-axis voltage amplitude limit value;

the power battery heating module 850 is configured to provide positive and negative abrupt voltage to the motor direct axis according to the real-time command of the motor direct axis voltage amplitude limit value, and generate a pulse current by using the motor direct axis inductance, so as to heat the power battery according to the pulse current. As an example, when the present embodiment provides positive and negative abrupt voltages to the motor direct shaft, waveforms of the voltages include, but are not limited to: square wave, sine wave, triangular wave or trapezoidal wave.

It is understood that the present embodiment can periodically charge and discharge the power battery by generating the pulse current, thereby heating the power battery. In addition, the motor can be protected by combining the motor direct-axis current predicted value to adjust and generate the motor direct-axis voltage amplitude limit value real-time instruction, and the motor is prevented from being failed due to transient overcurrent of the real-time current of the motor direct axis. In addition, before the positive and negative abrupt change voltage is provided for the motor direct axis, the motor cross axis current and the motor cross axis voltage can be controlled to be zero according to a motor torque equation, so that the motor torque is avoided, and the damage to power devices in a motor controller is reduced. The relationship between the temperature and time when the power battery is heated by the power battery heating scheme provided by the embodiment is shown in fig. 2. Therefore, the power battery heating scheme provided by the embodiment can enable the heating speed of the power battery to reach more than 2 cameras per minute. Compared with other existing heating schemes, the heating efficiency is improved, and the heating time is saved. In this embodiment, the circuit connection when the power battery is discharged is shown in fig. 6, and the circuit connection when the power battery is charged is shown in fig. 7.

In the heating process of the power battery, the motor winding resistance and the motor direct-axis inductance change due to the physical characteristics of motor temperature change, inductance saturation and the like, so that phase current transient overcurrent is caused, and therefore, the motor direct-axis current needs to be controlled to avoid overcurrent. Specifically, in an exemplary embodiment, the process of predicting the current of the motor direct shaft to obtain the predicted value of the current of the motor direct shaft may include: acquiring a motor direct-axis inductance value and a motor direct-axis voltage amplitude value of a current power battery heating period; inputting the motor direct-axis inductance value and the motor direct-axis voltage amplitude value of the current power battery heating period into a current calculation equation, and predicting the motor direct-axis current variation of the next power battery heating period and the motor direct-axis current value of the next power battery heating period; wherein the current calculation equation includes:wherein Ud represents the motor direct-axis voltage amplitude value, L of the current power battery heating period _d Represents the direct axis inductance value of the motor, < >>The direct-axis current variation of the motor is shown, and t is the time of the heating cycle of the power battery. In addition, after obtaining the predicted value of the motor direct-axis current, the embodiment may further include: and comparing the motor direct-axis current predicted value with a motor direct-axis current limit value corresponding to the motor direct-axis current limit value initial instruction, and reversing the motor direct-axis voltage amplitude limit value corresponding to the motor direct-axis voltage amplitude limit value initial instruction when the motor direct-axis current predicted value is larger than the motor direct-axis current limit value, so as to carry out overcurrent protection on the motor through the reverse action of voltage.

According to the above description, in another exemplary embodiment, the process of predicting the current of the motor direct shaft to obtain the predicted value of the current of the motor direct shaft according to the present embodiment may further include: and calculating a current difference value between the motor straight-axis current value of the current power battery heating period and the motor straight-axis current value of the previous power battery heating period, and predicting the motor straight-axis current value of the next power battery heating period based on the current difference value. In addition, after obtaining the predicted value of the motor direct-axis current, the embodiment may further include: and comparing the motor direct-axis current predicted value with a motor direct-axis current correction limit value, and reversing the motor direct-axis voltage amplitude correction limit value when the motor direct-axis current predicted value is larger than the motor direct-axis current correction limit value so as to carry out overcurrent protection on the motor through the reverse action of voltage.

Therefore, since the motor controller has time delay when generating the control voltage, the embodiment can predict the current of the motor direct shaft, then control the current according to the predicted current, and avoid the overcurrent of the motor direct shaft current, thereby protecting the motor.

In an exemplary embodiment, based on the motor direct-axis voltage amplitude limit real-time command, the process of providing positive and negative abrupt voltages to the motor direct-axis may include: responding to a real-time instruction of the amplitude limit value of the motor direct-axis voltage, and acquiring a motor torque equation; based on a motor torque equation, after motor quadrature current and motor quadrature voltage are controlled to be zero respectively, positive and negative abrupt change voltages are provided for a motor direct axis. As an example, when the present embodiment provides positive and negative abrupt voltages to the motor direct shaft, waveforms of the voltages include, but are not limited to: square wave, sine wave, triangular wave or trapezoidal wave. As an example, when the present embodiment heats the power battery according to the circuit connection shown in fig. 4, the motor is in a state of a lower three-pipe short circuit or an upper three-pipe short circuit, in which a current flows inside the motor without entering the battery, and therefore, the use of a voltage vector corresponding to the lower three-pipe short circuit or the upper three-pipe short circuit should be reduced as much as possible, and it is required that the effective value of the given motor straight-axis voltage amplitude Ud is as large as possible, so that the present embodiment can select a square wave as the most effective waveform corresponding to the straight-axis voltage command. In the circuit connection shown in fig. 4, the lower three transistors may be constituted by a mosfet U2, a mosfet V2, and a mosfet W2; the upper three transistors may be formed by a mosfet U1, a mosfet V1 and a mosfet W1. The voltage vector of the lower three-tube short circuit may be set to 000 and the voltage vector of the upper three-tube short circuit may be set to 111.

In an exemplary embodiment, before acquiring the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command, which are generated in advance or in real time, the embodiment may further include:

detecting whether the motor has a fault or not, and detecting whether a motor controller has a fault or not;

if the motor has no fault, the motor controller normally receives a power battery heating instruction sent from the outside, and if the motor controller has no fault inside, a motor straight shaft voltage amplitude limit value initial instruction and a motor straight shaft current limit value initial instruction which are generated in advance or in real time are obtained;

if the motor fails, the motor controller can not normally receive the power battery heating command sent from the outside and/or the motor controller fails, and the acquisition of the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command which are generated in advance or in real time is stopped.

It can be seen that, before the initial command of the motor direct-axis voltage amplitude limit value and the initial command of the motor direct-axis current limit value are generated, the embodiment can check whether the function can be normally started, and the starting conditions include but are not limited to: 1) Receiving an instruction of starting a function of an upper controller; 2) No fault exists in the motor controller; 3) No faults exist in the motor.

In another exemplary embodiment of the present invention, the embodiment provides a power cell heating system for performing the steps of:

step A is implemented: it is checked whether the function can be normally turned on, and the starting conditions include, but are not limited to: 1) Receiving an instruction of starting a function of an upper controller; 2) No fault exists in the motor controller; 3) No faults exist in the motor.

And (B) implementing the step (B): after the function is normally turned on, d-axis voltage amplitude limit and current limit commands need to be generated. According to the motor torque equation, if torque is to be avoided, the q-axis current needs to be controlled to 0, and therefore, the q-axis voltage should be given to 0, and the q-axis current is controlled to 0. Meanwhile, given positive and negative alternating d-axis voltage, alternating current is generated by using d-axis inductance of the motor, and as the d-axis voltage is always given by a modulation algorithm, the situation that six bridge arms are completely turned off does not exist, so that current cannot flow to a bus battery through a body diode, and a power module cannot be damaged. The d-axis voltage amplitude limit value and the current limit value command can be preset values, and can also be generated according to the state of a three-electric system, such as setting the d-axis voltage amplitude limit value according to the bus voltage. In this embodiment, the three-electric system includes, but is not limited to, a motor controller, and a power battery in the new energy vehicle.

And C, implementing the step: and adjusting the real-time d-axis voltage amplitude limit value instruction. In the motor control modulation algorithm, when the voltage vector is 000 or 111, the motor is in a state of a lower three-pipe short circuit or an upper three-pipe short circuit, and in this state, current flows inside the motor without entering the battery. Thus, the use of these two vectors should be reduced as much as possible, so the effective value of a given d-axis voltage amplitude Ud needs to be as large as possible, so the most effective waveform for the d-axis voltage amplitude limit command is a square wave. The waveform of the d-axis voltage amplitude Ud is shown in fig. 5. In the working process, the resistance of the motor winding and the d-axis inductance can be changed due to the physical characteristics of motor temperature change, inductance saturation and the like, so that phase current transient state overcurrent is caused. Therefore, it is necessary to control the d-axis current to avoid overcurrent. The d-axis current may be controlled by reversing the d-axis voltage amplitude limit command value when the d-axis current is detected to be excessively large, and the d-axis current may be rapidly reduced by the reverse action of the voltage.

And D, implementing the step: the d-axis voltage amplitude limit and the d-axis current limit can be corrected by integrating a plurality of factors. Due to changes in external conditions, such as changes in water temperature, changes in voltage, electrical drive system or battery system failures, such as over-temperature, or over-voltage failures, may be caused. Therefore, the d-axis voltage amplitude limit and the d-axis current monitoring threshold need to be integrated with each temperature information, and the voltage information is dynamically adjusted, including but not limited to water temperature, stator temperature, rotor temperature, power module temperature, etc.

And E, implementing the step: in order to achieve better current control effect, the d-axis current is predicted. Because the delay condition exists in the final generated control voltage is calculated, a current prediction module is needed to predict the d-axis current, and the prediction method can be as follows: predicting the current of the next period through the current difference value of the last two periods, and adopting a control strategy in advance. The prediction method may also be: by d-axis inductance value L in motor parameters calibrated in advance _d By means ofTo predict the current variation of the next cycle and the current value of the next cycle.

The relationship between the temperature and time when the power battery is heated by the power battery heating scheme provided by the embodiment is shown in fig. 2. Therefore, the power battery heating scheme provided by the embodiment can enable the heating speed of the power battery to reach more than 2 cameras per minute. Compared with other existing heating schemes, the heating efficiency is improved, and the heating time is saved. In this embodiment, the circuit connection when the power battery is discharged is shown in fig. 6, and the circuit connection when the power battery is charged is shown in fig. 7. It is understood that the present embodiment can periodically charge and discharge the power battery by generating the pulse current, thereby heating the power battery. In addition, the motor can be protected by combining the motor direct-axis current predicted value to adjust and generate the motor direct-axis voltage amplitude limit value real-time instruction, and the motor is prevented from being failed due to transient overcurrent of the real-time current of the motor direct axis. In addition, before the positive and negative abrupt change voltage is provided for the motor direct axis, the motor cross axis current and the motor cross axis voltage can be controlled to be zero according to a motor torque equation, so that the motor torque is avoided, and the damage to power devices in a motor controller is reduced.

In summary, the invention provides a power battery heating system, which obtains an initial command of a motor direct-axis voltage amplitude limit value and an initial command of a motor direct-axis current limit value, which are generated in advance or in real time; then, correcting the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery to obtain a motor direct-axis voltage amplitude correction limit value; correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value; carrying out current prediction on the motor straight shaft to obtain a motor straight shaft current prediction value; the initial command of the motor direct-axis voltage amplitude limit value is adjusted through the motor direct-axis voltage amplitude correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current predicted value, so that the real-time command of the motor direct-axis voltage amplitude limit value is obtained; and finally, providing positive and negative abrupt change voltage for the motor direct shaft based on the real-time instruction of the motor direct shaft voltage amplitude limit value, and generating pulse current by utilizing the motor direct shaft inductance so as to heat the power battery according to the pulse current. It is known that the system can periodically charge and discharge the power battery by generating pulse current, thereby heating the power battery. In addition, the system generates a motor direct-axis voltage amplitude limit value real-time instruction by combining with the motor direct-axis current predicted value adjustment, so that the motor can be protected, and the motor is prevented from being failed due to transient overcurrent of the real-time current of the motor direct axis. In addition, before the positive and negative abrupt change voltage is provided for the motor direct shaft, the system can control the motor cross shaft current and the motor cross shaft voltage to be zero according to a motor torque equation, so that the generation of motor torque is avoided, and the damage to power devices in a motor controller is reduced.

It should be noted that, the power battery heating system provided in the above embodiment and the power battery heating method provided in the above embodiment belong to the same concept, and the specific manner in which each module performs the operation has been described in detail in the method embodiment, which is not repeated here. In practical application, the power battery heating system provided in the above embodiment may be configured by different functional modules according to needs, that is, the internal structure of the system is divided into different functional modules to complete all or part of the functions described above, which is not limited herein.

In another embodiment of the present invention, the embodiment also provides a vehicle electric drive apparatus for performing the power battery heating method as described in some embodiments or some embodiments above. As an example, the vehicle electric drive apparatus in the present embodiment may be constituted by an electric motor. It should be noted that, the vehicle electric driving device provided in the present embodiment and the power battery heating method provided in the foregoing embodiment belong to the same concept, where a specific manner of performing an operation of the vehicle electric driving device has been described in detail in the foregoing method embodiment, and the corresponding technical effects are only required by referring to the foregoing method embodiment, and this implementation is not repeated herein.

The above embodiments are performed with or without user consent when processing related data (e.g., d-axis voltage amplitude limit command and d-axis current limit command, power battery heating environment data, etc.), such as collecting, storing, using, processing, transmitting, providing, disclosing, deleting, etc. For example, the power battery heating environment data is authorized if the user knows and agrees; either the user is actively provided after reading the relevant description, or the user is actively authorized/provided/uploaded, or otherwise obtained through or informed of the user's consent, while using some or all of the functions described in the above embodiments.

The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims (10)

1. A method for heating a power battery, comprising the steps of:

acquiring a motor direct-axis voltage amplitude limit value initial instruction and a motor direct-axis current limit value initial instruction which are generated in advance or in real time;

correcting the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery to obtain a motor direct-axis voltage amplitude correction limit value; correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value;

current prediction is carried out on the motor straight shaft to obtain a motor straight shaft current prediction value;

the initial command of the motor direct-axis voltage amplitude value is adjusted through the motor direct-axis voltage amplitude value correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current predicted value, so that a real-time command of the motor direct-axis voltage amplitude value is obtained;

based on the real-time instruction of the amplitude limit value of the motor direct-axis voltage, positive and negative abrupt change voltage is provided for the motor direct-axis, and pulse current is generated by utilizing the motor direct-axis inductance so as to heat the power battery according to the pulse current.

2. The method of claim 1, wherein the step of predicting the current of the motor's straight shaft to obtain a predicted value of the current of the motor's straight shaft comprises:

acquiring a motor direct-axis inductance value and a motor direct-axis voltage amplitude value of a current power battery heating period;

inputting the motor direct-axis inductance value and the motor direct-axis voltage amplitude value of the current power battery heating period into a current calculation equation, and predicting the motor direct-axis current variation of the next power battery heating period and the motor direct-axis current value of the next power battery heating period; wherein the current calculation equation includes:wherein Ud represents the motor direct-axis voltage amplitude value, L of the current power battery heating period _d Represents the direct axis inductance value of the motor, < >>The direct-axis current variation of the motor is shown, and t is the time of the heating cycle of the power battery.

3. The method of claim 1, wherein the step of predicting the current of the motor's straight shaft to obtain a predicted value of the current of the motor's straight shaft comprises:

and calculating a current difference value between the motor straight-axis current value of the current power battery heating period and the motor straight-axis current value of the previous power battery heating period, and predicting the motor straight-axis current value of the next power battery heating period based on the current difference value.

4. A power cell heating method according to claim 2 or 3, wherein after obtaining the predicted value of the motor direct-axis current, the method further comprises:

comparing a motor direct-axis current predicted value with a motor direct-axis current limit value corresponding to the motor direct-axis current limit value initial instruction, and reversing a motor direct-axis voltage amplitude limit value corresponding to the motor direct-axis voltage amplitude limit value initial instruction when the motor direct-axis current predicted value is larger than the motor direct-axis current limit value, so as to carry out overcurrent protection on the motor through the reverse action of voltage;

or comparing the motor direct-axis current predicted value with the motor direct-axis current correction limit value, and reversing the motor direct-axis voltage amplitude correction limit value when the motor direct-axis current predicted value is larger than the motor direct-axis current correction limit value so as to carry out overcurrent protection on the motor through the reverse action of voltage.

5. The method of claim 1, wherein providing positive and negative abrupt voltage to the motor shaft based on the motor shaft voltage amplitude limit real-time command comprises:

responding to the real-time instruction of the amplitude limit value of the motor direct-axis voltage, and acquiring a motor torque equation;

And based on the motor torque equation, after the motor quadrature current and the motor quadrature voltage are controlled to be zero, positive and negative abrupt change voltages are provided for the motor direct axis.

6. The method according to claim 1 or 5, wherein when the positive and negative abrupt voltage is supplied to the motor straight shaft, the waveform of the voltage includes: square wave, sine wave, triangular wave or trapezoidal wave.

7. The power battery heating method according to claim 1, characterized in that, before acquiring the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command, which are generated in advance or in real time, the method further comprises:

detecting whether the motor has a fault or not, and detecting whether a motor controller has a fault or not;

if the motor has no fault, the motor controller normally receives a power battery heating instruction sent from the outside, and if the motor controller has no fault, a motor direct-axis voltage amplitude limit value initial instruction and a motor direct-axis current limit value initial instruction which are generated in advance or in real time are obtained;

if the motor fails, the motor controller can not normally receive the power battery heating command sent from the outside, and/or if the motor controller fails, the motor controller stops acquiring the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command which are generated in advance or in real time.

8. The power battery heating method according to claim 1 or 7, wherein the generation process of the motor direct-axis voltage amplitude limit value initial command and the motor direct-axis current limit value initial command includes:

and generating the initial command of the amplitude limit value of the motor direct-axis voltage and the initial command of the current limit value of the motor direct-axis in advance or in real time according to the state of the motor, the state of the motor controller and the state of the power battery.

9. A power cell heating system, comprising:

the initial command module is used for acquiring a motor direct-axis voltage amplitude limit value initial command and a motor direct-axis current limit value initial command which are generated in advance or in real time;

the correction module is used for correcting the motor direct-axis voltage amplitude limit value corresponding to the initial command of the motor direct-axis voltage amplitude limit value according to the heating environment of the power battery to obtain a motor direct-axis voltage amplitude correction limit value; correcting the motor direct-axis current limit value corresponding to the initial command of the motor direct-axis current limit value according to the heating environment of the power battery to obtain a motor direct-axis current correction limit value;

the current prediction module is used for predicting the current of the motor straight shaft to obtain a motor straight shaft current predicted value;

The command adjustment module is used for adjusting the initial command of the motor direct-axis voltage amplitude limit value through the motor direct-axis voltage amplitude correction limit value, the motor direct-axis current correction limit value and the motor direct-axis current predicted value to obtain a real-time command of the motor direct-axis voltage amplitude limit value;

and the power battery heating module is used for providing positive and negative abrupt change voltage for the motor direct shaft according to the real-time instruction of the voltage amplitude limit value of the motor direct shaft, and generating pulse current by utilizing the inductance of the motor direct shaft so as to heat the power battery according to the pulse current.

10. A vehicle electric drive apparatus for performing the power battery heating method according to any one of claims 1 to 7.