Method, control device and computer storage medium for battery pack self-heating

Abstract

The present application relates to the technical field of vehicle batteries, and more specifically to a method for self-heating a battery pack, a control device for implementing the method, a computer storage medium for implementing the method, and a computer program product. The method includes: determining the d and q axis reference currents under the motor control strategy based on the self-heating instruction, wherein the motor control strategy indicates that the motor torque is zero and generates positive and negative alternating high-frequency pulses on the DC side for heating the battery pack; based on the rotor position information, converting the d and q axis reference currents in the two-phase rotating coordinate system to the three-phase reference current in the three-phase stationary coordinate system; receiving the three-phase feedback current collected by the current sensor; and performing current hysteresis control so that the deviation between the three-phase reference current and the three-phase feedback current is within the threshold range.

Description

Technical Field

[0001] The present application relates to the technical field of vehicle batteries, and more specifically to a method for self-heating a battery pack, a control device for implementing the method, a computer storage medium for implementing the method, and a computer program product. Background Art

[0002] With the increasingly severe energy and environmental problems and the continuous advancement of three-electric technology, new energy vehicles are gradually gaining wider popularity. In customer feedback on new energy vehicles, problems related to battery charging and discharging (such as long charging time, insufficient cruising range, power limitation, etc.) have significantly affected customers' driving experience. These problems are mainly caused by the influence of ambient temperature on the activity of lithium ions in lithium batteries, which in turn affects the cruising range, charging and discharging efficiency, and may even lead to power limitation during driving, and vehicles equipped with automatic start-stop function cannot be started, etc., endangering the functional safety of the entire vehicle. Therefore, in order to ensure a good driving experience and functional safety, during vehicle operation and charging, efforts should be made to maintain the battery pack within an appropriate temperature range to enhance the activity of lithium ions and ensure efficient charging and discharging.

[0003] Traditional battery pack heating solutions mostly rely on external media, such as using waste heat generated by the engine or motor stall to maintain the battery pack temperature through heat exchange in the cooling system. Although this method effectively utilizes waste heat resources, it has high requirements for the design of the cooling system and has limited heat conduction efficiency. Especially when the vehicle is stationary, it may also introduce unnecessary energy loss and affect economic efficiency.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] In order to solve or at least alleviate one or more of the above problems, the following technical solutions are provided. The embodiments of the present application provide a method for self-heating of a battery pack, a control device for implementing the method, a computer storage medium for implementing the method, and a computer program product, which can realize self-heating of the battery pack without relying on an external heat conduction medium, while suppressing unexpected torque during the heating process of the battery pack and avoiding the generation of vehicle vibration and noise.

[0006] According to a first aspect of the present application, a method for self-heating of a battery pack is provided, the method comprising the following steps: determining the d-axis and q-axis reference currents under a motor control strategy based on a self-heating instruction, wherein the motor control strategy indicates that the motor torque is zero and generates alternating positive and negative high-frequency pulses on the DC side for heating the battery pack; based on rotor position information, converting the d-axis and q-axis reference currents in a two-phase rotating coordinate system into three-phase reference currents in a three-phase stationary coordinate system; receiving a three-phase feedback current collected by a current sensor; and performing current hysteresis control so that the deviation between the three-phase reference current and the three-phase feedback current is within a threshold range.

[0007] As an alternative or supplement to the above scheme, in a method for battery pack self-heating according to an embodiment of the present application, based on the self-heating instruction, determining the d-axis and q-axis reference currents under the motor control strategy includes: setting the amplitude of the q-axis reference current to zero; or the method also includes: controlling the sum of the components of the three-phase reference current on the q-axis to be zero.

[0008] As an alternative or supplement to the above solution, in a method for self-heating of a battery pack according to an embodiment of the present application, the d-axis reference current is a high-frequency square wave with controllable amplitude and duty cycle.

[0009] As an alternative or supplement to the above scheme, in a method for battery pack self-heating according to an embodiment of the present application, based on the self-heating instruction, determining the d-axis and q-axis reference currents under the motor control strategy includes: determining the amplitude and duty cycle of the d-axis reference current based on the difference between the desired temperature of the battery pack and the ambient temperature and the desired heating time.

[0010] As an alternative or supplement to the above scheme, in a method for self-heating of a battery pack according to an embodiment of the present application, determining the d-axis and q-axis reference currents under the motor control strategy based on the self-heating instruction includes: determining the frequency of the d-axis reference current based on the polarization characteristics of the battery cells in the battery pack.

[0011] As an alternative or supplement to the above scheme, in a method for self-heating of a battery pack according to an embodiment of the present application, based on the rotor position information, the d and q axis reference currents in a two-phase rotating coordinate system are converted to three-phase reference currents in a three-phase stationary coordinate system, including: converting the d and q axis reference currents in the two-phase rotating coordinate system into α and β axis reference currents in the two-phase stationary coordinate system through Park inverse transformation; and converting the α and β axis reference currents in the two-phase stationary coordinate system into a, b and c axis reference currents in the three-phase stationary coordinate system through Clark inverse transformation.

[0012] As an alternative or supplement to the above scheme, in a method for battery pack self-heating according to an embodiment of the present application, current hysteresis control is performed on the three-phase current so that the deviation between the three-phase reference current and the three-phase feedback current is within a threshold range, including: if the deviation exceeds the threshold range, reducing the deviation by controlling the switching state of the switching tube in the inverter.

[0013] As an alternative or supplement to the above solution, in a method for self-heating of a battery pack according to an embodiment of the present application, the method further includes: if the temperature of the battery pack reaches a temperature threshold, exiting the self-heating mode.

[0014] According to the second aspect of the present application, a control device is provided, comprising: a memory; a processor; and a computer program stored on the memory and executable on the processor, wherein the execution of the computer program enables any one of the methods for self-heating of a battery pack described in the first aspect of the present application to be executed.

[0015] According to a third aspect of the present application, a computer storage medium is provided, wherein the computer storage medium comprises instructions, and the instructions, when run, execute any one of the methods for self-heating of a battery pack according to the first aspect of the present application.

[0016] According to a fourth aspect of the present application, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements any one of the methods for self-heating of a battery pack described in the first aspect of the present application.

[0017] The battery pack self-heating solution according to one or more embodiments of the present application can generate alternating positive and negative high-frequency pulses on the DC side, thereby utilizing the internal resistance of the battery pack to generate heat to achieve self-heating, while avoiding dependence on external heat conduction media. The solution can also suppress unexpected torque during battery pack heating and avoid vehicle jitter and noise. In addition, the solution uses a current hysteresis control strategy in a three-phase stationary coordinate system to track and control transient currents of high-frequency conversions, solving the problem that traditional PI control is difficult to track changing signals, while improving the system response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or other aspects and advantages of the present application will become clearer and easier to understand through the following description of various aspects in conjunction with the accompanying drawings, in which the same or similar units are represented by the same reference numerals. In the accompanying drawings:

[0019] Figure 1 is a schematic block diagram of a motor control system according to one or more embodiments of the present application;

[0020] Figure 2is a schematic flow chart of a method 20 for self-heating a battery pack according to one or more embodiments of the present application;

[0021] Figure 3 is an exemplary schematic diagram of current vectors in a three-phase stationary coordinate system and a two-phase rotating coordinate system according to one or more embodiments of the present application;

[0022] Figure 4 is a schematic block diagram of a control device 40 according to one or more embodiments of the present application. DETAILED DESCRIPTION

[0023] The description of the following specific embodiments is merely exemplary in nature and is not intended to limit the disclosed technology or the application and use of the disclosed technology. In addition, it is not intended to be bound by any express or implied theory presented in the aforementioned technical field, background technology or the following specific embodiments.

[0024] In the following detailed description of the embodiments, many specific details are set forth in order to provide a more thorough understanding of the disclosed technology. However, it is apparent to one of ordinary skill in the art that the disclosed technology can be practiced without these specific details. In other instances, well-known features are not described in detail to avoid unnecessarily complicating the description.

[0025] Terms such as "comprising" and "including" indicate that in addition to the units and steps directly and clearly stated in the specification, the technical solution of the present application does not exclude the situation of having other units and steps that are not directly or clearly stated. Terms such as "first" and "second" do not indicate the order of units in terms of time, space, size, etc., but are only used to distinguish between units.

[0026] Hereinafter, various exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings.

[0027] Referring to the accompanying drawings, Figure 1 is a schematic block diagram of a motor control system according to one or more embodiments of the present application.

[0028] like Figure 1 As shown, the motor control system includes a high-voltage battery pack 110 , a motor control module 120 , an inverter 130 , and a motor 140 .

[0029] The inverter 130 includes a three-phase bridge arm, an energy storage capacitor, a current sensor, etc. Each phase bridge arm includes an upper and lower part, each part of which is controlled by a switch tube (for example, an insulated gate bipolar transistor (IGBT)) to control the on and off of its circuit, and the switch tube parallel diode is used for current flow. Exemplarily, the motor 140 is a permanent magnet synchronous motor commonly used in electric drive systems, including a three-phase winding, and the three-phase winding is connected to the current sensor of the inverter 130 through a busbar. The function of the motor controller 120 is to generate a drive signal for the switch tube according to the requirements of the upper computer, thereby controlling the periodic on and off of the switch tubes of each bridge arm to generate a voltage signal for driving the motor 140.

[0030] As mentioned above, some battery pack heating solutions rely on external media, using waste heat generated by the engine or motor stall to maintain the battery pack temperature through heat exchange in the cooling system. Compared with such solutions, the motor control system according to the present application can achieve self-heating of the battery pack without relying on external heat transfer media. Since there are no additional components, the cost increase is avoided.

[0031] In addition, some methods for battery pack self-heating use the switching devices of the motor controller and the internal inductance of the motor to form a charge and discharge circuit, and then use the corresponding control strategy to give the desired pulse to control the switching devices, so that the battery pack side generates alternating positive and negative pulse currents to achieve internal self-heating of the battery pack. However, in the above methods, no attention has been paid to the influence of the unexpected torque of the motor, so that in the process of heating the battery pack when the vehicle is stationary, due to the mutual influence of the stator and rotor magnetic fields, a constant or constantly changing torque will be generated at the shaft end, causing the body to shake and bring noise problems. In response to this, the present application proposes a battery pack self-heating scheme that can achieve self-heating of the battery pack without relying on an external heat conduction medium, while suppressing unexpected torque during the battery pack heating process. In the following, it will be described in detail with reference to the accompanying drawings.

[0032] Figure 2 is a schematic flow chart of a method 20 for self-heating a battery pack according to one or more embodiments of the present application.

[0033] The core of method 20 is to generate alternating positive and negative high-frequency current on the DC bus side through appropriate control strategies, which flows through the internal resistance of the battery pack to generate Joule heat and heat the battery pack itself. During the execution of method 20, the generation of motor torque must be avoided, otherwise it will cause problems such as noise and vehicle shaking.

[0034] like Figure 2 As shown, in step S210, based on the self-heating instruction, the d-axis and q-axis reference currents under the motor control strategy are determined.

[0035] In order to achieve motor control, the field-oriented control strategy has been widely used due to its stability and easy implementation. The core idea of ​​the field-oriented control strategy is to transform the three-phase current into the d-axis component of the control magnetic field and the q-axis component of the control torque through coordinate transformation. By adjusting the two components, weak magnetic control in the high-speed area and torque control in the full-speed area can be achieved. For example, according to the torque formula of the permanent magnet synchronous motor:

[0036]

[0037] in, is the motor torque, is the number of motor pole pairs, is the d-axis current, is the q-axis current, is the permanent magnet flux, is the d-axis inductance, is the q-axis inductance.

[0038] In order to avoid unexpected torque during battery pack heating, it is necessary to use the motor control strategy to adjust the d and q axis reference currents so that the motor torque is zero. Proportional to By adjusting Reference value , you can The actual feedback value By controlling it to be near 0, the motor torque can be avoided at any rotor position. is zero.

[0039] In order to avoid polarization and energy loss of the battery cell electrodes, it is necessary to generate alternating positive and negative high-frequency pulses on the DC side during the battery pack heating process. In the control process, the freewheeling effect of the three-phase inductance of the motor can be used to apply a high-frequency square wave command with controllable amplitude and duty cycle to it, and the positive and negative alternating currents on the DC side can be generated through the charging and discharging of the motor inductance. That is, the d-axis reference current Set to a high frequency square wave with controllable amplitude and duty cycle.

[0040] Specifically, the required heating power can be calculated based on the difference between the expected battery pack temperature and the ambient temperature and the expected heating time, and then the D-axis reference current can be determined through the thermal model or experimental data of the motor. The amplitude and duty cycle should be selected to ensure that the heating requirements are met without exceeding the thermal limitations of the motor. In addition, the d-axis reference current The choice of frequency can be based on the polarization characteristics of the battery cells in the battery pack and / or the electrical characteristics of the motor. Too high a frequency may cause irreversible chemical reactions or structural changes inside the battery cells, while too low a frequency may not effectively utilize the inductance effect of the motor.

[0041] In step S220, based on the rotor position information, the d-axis and q-axis reference currents in the two-phase rotating coordinate system are converted into three-phase reference currents in the three-phase stationary coordinate system.

[0042] In the actual control process, since the d-axis current changes with time at a high frequency, it is difficult for traditional PI control to track the changing signal. Therefore, a current hysteresis control strategy in a three-phase stationary coordinate system can be adopted to achieve tracking and control of the instantaneous current.

[0043] Optionally, in order to achieve control of d and q axis currents that meet the above requirements, based on the rotor position information, the d and q axis reference currents in the two-phase rotating coordinate system can be converted into α and β axis reference currents in the two-phase stationary coordinate system through Park inverse transformation, and then the α and β axis reference currents in the two-phase stationary coordinate system can be converted into a, b, and c axis reference currents in the three-phase stationary coordinate system through Clark inverse transformation.

[0044] Additionally or alternatively, the reference currents of the a, b, and c axes in the three-phase stationary coordinate system can also be given according to the rotor position and the three-phase current vector relationship. When the rotor is at any position and the angle between the d axis of the two-phase rotating coordinate system and the a axis of the three-phase stationary coordinate system is θ, according to Figure 3 The vector relationship requires that the sum of the three-phase current components on the q axis in the three-phase stationary coordinate system is zero. Combined with the three-phase symmetrical system, the sum of the three-phase current vectors is zero, and we can get:

[0045]

[0046] in, is a preset value and can be adjusted based on the difference between the expected battery pack temperature and the ambient temperature and the expected heating time. is an extreme value and presents an adjustable fixed-period triangular wave. In order to avoid the generation of motor torque, the sum of the components of the three-phase reference current on the q axis can be set to zero.

[0047] In step S230, three-phase feedback current collected by the current sensor is received.

[0048] In step S240, current hysteresis control is performed so that the deviation between the three-phase reference current and the three-phase feedback current is within a threshold range.

[0049] Hysteresis Current Control, also known as hysteresis modulation or Bang-Bang control, is a current control method for inverters. This method compares the reference current (i.e. the desired current value) with the actual current (i.e. the feedback current value) and controls the on and off of the switch tube (such as IGBT) based on the deviation between them to maintain the current within a predetermined range.

[0050] Exemplarily, the deviation between the three-phase reference current and the three-phase feedback current is first determined, and it is determined whether the deviation exceeds a threshold range (i.e., a hysteresis threshold), where the hysteresis threshold defines an acceptable current deviation range. If the deviation exceeds the threshold range, the deviation can be reduced by controlling the switching state of the switch tube in the inverter. In the above manner, when the control tends to be stable, the three-phase feedback current changes around the three-phase reference current, and the deviation is maintained within an acceptable limit. Through the above-mentioned coordinate transformation and current hysteresis control in a three-phase stationary coordinate system, rapid tracking and control of high-frequency changing d-axis current can be achieved. This control method is simple to operate, does not depend on motor parameters, and has strong robustness.

[0051] Optionally, if the battery pack temperature reaches a temperature threshold, the self-heating mode is exited.

[0052] According to one or more embodiments of the present application, method 20 can generate alternating positive and negative high-frequency pulses on the DC side, thereby utilizing the internal resistance heat of the battery pack to achieve self-heating, while avoiding dependence on external heat conduction media. Method 20 can also suppress unexpected torque during battery pack heating and avoid vehicle jitter and noise. In addition, method 20 uses a current hysteresis control strategy in a three-phase stationary coordinate system to track and control transient currents of high-frequency conversions, solving the problem that traditional PI control is difficult to track changing signals, while improving the system response speed.

[0053] Figure 4 4 is a schematic block diagram of a control device 40 according to one or more embodiments of the present application. The control device 40 includes a memory 410, a processor 420, and a computer program 430 stored in the memory 410 and executable on the processor 420. The execution of the computer program 430 enables the following Figure 2 The illustrated method 20 for battery pack self-heating is performed.

[0054] In addition, as described above, the present application can also be implemented as a computer storage medium, in which there is stored a program for causing a computer to execute the following steps: Figure 1The program of the method 20 for self-heating a battery pack shown in the figure. Here, as the computer storage medium, various computer storage media such as disks (e.g., magnetic disks, optical disks, etc.), cards (e.g., memory cards, optical cards, etc.), semiconductor memories (e.g., ROMs, non-volatile memories, etc.), and tapes (e.g., magnetic tapes, cassette tapes, etc.) can be used.

[0055] The present application may also be implemented as a computer program product, which includes a computer program. When the computer program is executed by a processor, the following Figure 1 The procedure of method 20 for battery pack self-heating is shown.

[0056] In the applicable situation, hardware, software or a combination of hardware and software can be used to realize the various embodiments provided by the application. Moreover, in the applicable situation, without departing from the scope of the application, the various hardware components and / or software components set forth herein can be combined into a composite component comprising software, hardware and / or both. In the applicable situation, without departing from the scope of the application, the various hardware components and / or software components set forth herein can be divided into subcomponents comprising software, hardware or both. In addition, in the applicable situation, it is contemplated that the software component can be implemented as a hardware component, and vice versa.

[0057] Software according to the present application (such as program code and / or data) can be stored on one or more computer storage media. It is also contemplated that the software identified herein can be implemented using one or more general or special-purpose computers and / or computer systems, networked and / or otherwise. Where applicable, the order of the various steps described herein can be changed, combined into composite steps, and / or divided into sub-steps to provide the features described herein.

[0058] The embodiments and examples set forth herein are provided to best illustrate embodiments according to the present application and its specific applications, and thereby enable those skilled in the art to implement and use the present application. However, those skilled in the art will appreciate that the above description and examples are provided only for ease of illustration and example. The description set forth is not intended to cover all aspects of the present application or to limit the present application to the precise form disclosed.

Claims

1. A method for self-heating a battery pack, characterized in that: The method comprises the following steps: Based on the self-heating instruction, determining the d-axis and q-axis reference currents under the motor control strategy, wherein the motor control strategy indicates that the motor torque is zero and generates alternating positive and negative high-frequency pulses on the DC side for heating the battery pack; Based on the rotor position information, the d-axis and q-axis reference currents in the two-phase rotating coordinate system are converted into the three-phase reference currents in the three-phase stationary coordinate system; receiving three-phase feedback current collected by a current sensor; and Performing current hysteresis control so that the deviation between the three-phase reference current and the three-phase feedback current is within a threshold range, Wherein, based on the self-heating instruction, determining the d-axis and q-axis reference currents under the motor control strategy includes: determining the frequency of the d-axis reference current based on the polarization characteristics of the battery cells in the battery pack.

2. The method for self-heating of a battery pack according to claim 1, characterized in that: Based on the self-heating instruction, determining the d-axis and q-axis reference currents under the motor control strategy includes: setting the amplitude of the q-axis reference current to zero; or The method further includes: controlling the sum of the components of the three-phase reference current on the q-axis to be zero.

3. The method for self-heating of a battery pack according to claim 1, characterized in that: The d-axis reference current is a high-frequency square wave with controllable amplitude and duty cycle.

4. The method for self-heating of a battery pack according to claim 1, characterized in that: Based on the self-heating instruction, the d-axis and q-axis reference currents under the motor control strategy are determined as follows: The magnitude and duty cycle of the d-axis reference current are determined based on the difference between the desired battery pack temperature and the ambient temperature and the desired heating time.

5. The method for self-heating of a battery pack according to claim 1, characterized in that: Based on the rotor position information, the d-axis and q-axis reference currents in the two-phase rotating coordinate system are converted to the three-phase reference currents in the three-phase stationary coordinate system, including: By Park inverse transformation, the d-axis and q-axis reference currents in the two-phase rotating coordinate system are converted into the α-axis and β-axis reference currents in the two-phase stationary coordinate system; and The α-axis and β-axis reference currents in the two-phase stationary coordinate system are converted into the a-axis, b-axis and c-axis reference currents in the three-phase stationary coordinate system through Clark inverse transformation.

6. The method for self-heating of a battery pack according to claim 1, characterized in that: Performing current hysteresis control so that the deviation between the three-phase reference current and the three-phase feedback current is within a threshold range includes: If the deviation exceeds a threshold range, the deviation is reduced by controlling the switching state of a switch tube in the inverter.

7. The method for self-heating of a battery pack according to claim 1, characterized in that: The method further comprises: If the battery pack temperature reaches a temperature threshold, the self-heating mode is exited.

8. A control device, characterized in that: The invention comprises: a memory; a processor; and a computer program stored in the memory and executable on the processor, wherein the execution of the computer program enables the method for self-heating of a battery pack according to any one of claims 1 to 7 to be executed.

9. A computer storage medium, characterized in that The computer storage medium includes instructions that, when executed, execute the method for self-heating of a battery pack according to any one of claims 1-7.

10. A computer program product, characterized in that It comprises a computer program, which, when executed by a processor, implements the method for self-heating of a battery pack according to any one of claims 1 to 7.

Images