Power battery heating method, device and power battery

Abstract

The present invention provides a power battery heating method, device and power battery, relating to the technical field of electric vehicles, including: receiving a battery heating instruction, generating a d-axis current instruction and a q-axis current instruction, wherein the q-axis current instruction is used to output a q-axis current with a value of zero; obtaining an initial d-axis current according to the d-axis current instruction; receiving a current frequency instruction, adjusting a time window, and generating a carrier according to the current frequency instruction; outputting a DC bias wave of the initial d-axis current through a bias loop and injecting it into a preset frequency of the carrier; feeding back the effective value of the initial d-axis current according to the time window, and outputting an effective DC voltage component through an effective value loop; injecting a target d-axis voltage according to the product of the effective DC voltage component and the carrier injecting the DC bias wave, so as to generate a high-frequency alternating target d-axis current for battery heating, overcoming the problem that a fixed current is applied during the battery heating process in the prior art, and the amplitude and frequency of the current cannot be accurately controlled, resulting in low heating efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and in particular to a power battery heating method, device and power battery. Background Art

[0002] With the rapid development of new energy vehicles, electric vehicles are increasingly used. However, in a low-temperature environment, the movement of the battery electrolyte in the electric vehicle slows down, and the charge and discharge performance of the battery decreases. Therefore, when in a low-temperature environment, in order to maintain the charge and discharge performance of the battery, the battery needs to be heated. Specifically, Joule heat can be generated by applying a high-frequency alternating current using the internal resistance of the battery to directly heat the battery cells.

[0003] During the power-on process, according to the heat formula of the battery, it can be known that the polarization voltage is related to the magnitude of the injected current. According to the electrochemical impedance spectrum, the impedance of the battery is different at different frequencies, resulting in different heat generation powers of the battery. However, the existing high-frequency alternating current applied is often fixed, unable to accurately control the current amplitude and frequency, and unable to effectively improve the heating efficiency. Summary of the Invention

[0004] In order to overcome the above technical defects, the purpose of the present invention is to provide a power battery heating method, device and power battery, which are used to overcome the problem that a fixed current is applied during the battery heating process, unable to accurately control the amplitude and frequency of the current, and with low heating efficiency.

[0005] The present invention discloses a power battery heating method, including:

[0006] Receiving a battery heating instruction, generating a d-axis current instruction and a q-axis current instruction, wherein the q-axis current instruction is used to output a q-axis current with a value of zero; obtaining an initial d-axis current according to the d-axis current instruction;

[0007] Receiving a current frequency instruction, adjusting a time window, and generating a carrier according to the current frequency instruction;

[0008] Outputting a DC bias wave of the initial d-axis current through a bias loop and injecting it into a preset frequency of the carrier;

[0009] Feeding back the effective value of the initial d-axis current according to the time window, and outputting an effective DC voltage component through an effective value loop;

[0010] Generating a target d-axis voltage according to the product of the effective DC voltage component and the carrier injecting the DC bias wave, so as to inject a high-frequency alternating current for battery heating.

[0011] Preferably, the outputting a DC bias wave of the initial d-axis current through a bias loop includes:

[0012] Calculate the offset value of the sine wave formed by the initial d-axis current relative to the preset axis according to the time window;

[0013] Receive an offset command, and use a PI controller to control the initial d-axis current according to the offset command and the offset value to output an offset with a value of zero, obtaining a DC offset wave.

[0014] Preferably, among the preset frequencies for injecting the carrier wave, it includes:

[0015] Superimpose the DC offset wave on the amplitude corresponding to the preset frequency in each period of the carrier wave to form a carrier wave injected with a DC offset wave.

[0016] Preferably, the method of feeding back the effective value of the initial d-axis current according to the time window and outputting an effective DC voltage component through an effective value loop includes:

[0017] Calculate the sampling frequency according to the time window, and generate a plurality of sampling periods according to the sampling frequency;

[0018] Calculate the effective value of the initial d-axis current within each sampling period;

[0019] Receive an effective value command, and generate an effective DC voltage component through a PI controller according to the effective values within each sampling period.

[0020] Preferably, the method of calculating the effective value of the initial d-axis current within each sampling period includes:

[0021] For any sampling period, square and sum the initial d-axis current values corresponding to each sampling point, then take the square root and average to obtain the effective value of the initial d-axis current.

[0022] Preferably, the sampling frequency and the time window are set to be reciprocal to each other.

[0023] Preferably, it further includes: injecting a tooth-by-tooth current on the q-axis.

[0024] Preferably, set the bandwidth of the offset loop to be lower than the bandwidth of the effective value loop.

[0025] The present invention also provides a power battery heating device, including:

[0026] A receiving module, configured to receive a battery heating command, generate a d-axis current command and a q-axis current command, wherein the q-axis current command is used to output a q-axis current with a value of zero; obtain an initial d-axis current according to the d-axis current command;

[0027] The first processing module is configured to receive a current frequency instruction, adjust a time window, and generate a carrier wave including several cycles according to the current frequency instruction; output a DC bias wave through a bias loop for the initial d-axis current, and inject it into a preset frequency in each cycle of the carrier wave;

[0028] The second processing module is configured to feedback the effective value of the initial d-axis current according to the time window, and output an effective DC voltage component through an effective value loop;

[0029] The execution module is configured to generate a target d-axis voltage according to the product of the effective DC voltage component and the carrier wave injected with the DC bias wave, so as to inject a high-frequency alternating current for battery heating.

[0030] The present invention also provides a power battery, which applies the above-mentioned power battery heating device.

[0031] After adopting the above technical solution, compared with the prior art, the following beneficial effects are achieved:

[0032] The power battery heating method provided by the present application has no additional energy storage components. It is flexible through the effective value loop, can quantitatively inject current amplitude control, and the introduction of the bias loop makes the control more stable, realizes high-precision injection frequency control, realizes precise control of the amplitude and frequency in the battery heating process, and improves the battery heating efficiency. Description of the Drawings

[0033] Figure 1 It is a flowchart of the first embodiment of the power battery heating method of the present invention;

[0034] Figure 2 It is a schematic diagram of the control process of the first embodiment of the power battery heating method of the present invention;

[0035] Figure 3 It is a reference diagram of the current waveform generated by experimental verification of the battery heating method applying the present embodiment in the first embodiment of the power battery heating method of the present invention;

[0036] Figure 4 It is a module schematic diagram of the second embodiment of the power battery heating device of the present invention.

[0037] Reference Signs:

[0038] 6 - Power battery heating device; 61 - Receiving module; 62 - First processing module; 63 - Second processing module; 63 - Execution module. Detailed Embodiments

[0039] The advantages of the present invention are further elaborated below in conjunction with the drawings and specific embodiments.

[0040] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0041] The terms used in this disclosure are for the purpose of describing particular embodiments only and are not intended to limit the present disclosure. The singular forms "a", "the", and "said" used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0042] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining".

[0043] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0044] In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "mounted", "connected", and "coupled" should be understood in a broad sense. For example, it may be a mechanical connection or an electrical connection, or it may be the communication inside two elements. It may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms may be understood according to specific circumstances.

[0045] In the subsequent description, the suffixes such as "module", "component", or "unit" used to represent elements are only for the convenience of describing the present invention, and they do not have a specific meaning in themselves. Therefore, "module" and "component" may be used interchangeably.

[0046] Embodiment 1: This embodiment discloses a power battery heating method, including the following:

[0047] S100: Receive a battery heating instruction, generate a d-axis current instruction and a q-axis current instruction. Among them, the q-axis current instruction (IqCmd) is used to output a q-axis current with a value of zero; obtain an initial d-axis current according to the d-axis current instruction;

[0048] In this embodiment, for illustration, in the control of the d-axis current and the q-axis current, the instruction control method is mostly adopted. After receiving the control instruction, feedback is executed. The initial d-axis current and the initial q-axis current can be obtained by Clarke and Park transformation of the three-phase current of the motor control. The initial q-axis current is controlled by a PI controller to output a q-axis current with a value of zero. Controlling the q-axis current output to zero is mainly used to limit the rotation of the motor, so that high-frequency current is injected into the d-axis to heat the battery. To further increase the safety during the battery heating process, it may further include: injecting a tooth-leaning current into the q-axis, increasing the tooth-leaning current, so as to increase the tooth-leaning torque to keep the driving gear and the driven gear always tightly meshed, thereby eliminating the influence of the tooth gap and reducing the mechanical vibration of the motor.

[0049] S200: Receive a current frequency instruction, adjust the time window, and generate a carrier according to the current frequency instruction;

[0050] In the above steps, the current frequency instruction (FreqCmd) contains a preset current frequency. According to this current frequency, a carrier in the form of a sine wave can be formed. The carrier is directly generated according to the given amplitude and frequency, which serves as the basis for the subsequent output of the d-axis voltage in this embodiment. Based on this basis, precise control of the current amplitude and frequency is achieved according to the following bias loop and effective value loop.

[0051] S300: Output a DC bias wave through the bias loop for the initial d-axis current, and inject it into the preset frequency of the carrier;

[0052] In the above steps, the bias loop is used to determine the bias of the initial d-axis current. This bias is the degree of deviation of the formed periodic sine wave from the preset axis. The introduction of the bias loop makes the control more stable. Specifically, the output of the DC bias wave by passing the initial d-axis current through the bias loop includes: calculating the bias value of the sine wave formed by the initial d-axis current relative to the preset axis according to the time window; receiving a bias instruction (OffsCmd), and controlling the initial d-axis current by a PI controller according to the bias instruction and the bias value to output a bias with a value of zero, thereby obtaining a DC bias wave.

[0053] It should be noted that the above time window is the operating frequency of the bias loop given by the current frequency command, which needs to be synchronized with the following RMS value loop. This bias command is used to give a PI controller a bias based on the initial d-axis current output value being zero, that is, there is a certain bias in the initial d-axis current. After being controlled by the PI controller based on the bias command, an output bias of approximately zero is obtained, that is, a DC bias wave is applied, so that the existing bias is eliminated, and this DC bias wave is the output in the above steps.

[0054] Specifically, in the preset frequency of injecting the carrier in the above steps, it includes: superimposing the DC bias wave on the amplitude corresponding to the preset frequency of each cycle of the carrier to form a carrier injecting the DC bias wave. It should be explained that the above carrier is generated according to the preset frequency and amplitude and is a periodic sine wave. In this embodiment, injecting the carrier is to superimpose this DC bias wave on the preset frequency of each cycle of the carrier. As an example, it can be assumed that one cycle of the carrier is 1000 Hz and 3000 μs, and the operating frequency of the bias loop obtained according to the time window is 100 Hz and 300 μs. This can divide each cycle of the carrier into 10 beats, and it is preset to superimpose the DC bias wave on the corresponding amplitude of the carrier in the first 3 beats of each cycle, that is, increase the amplitude of the first 3 beats, so that the amplitude change stability of the overall carrier is increased, and at the same time, high-precision injection frequency control is achieved, and the frequency can be smoothly changed in a wide range in real time.

[0055] In summary, in the above step S300, the carrier is a sine wave generated according to the frequency in the frequency command. Considering the problem of abnormal motor rotation, a first-level bias loop is added. The bias is obtained by averaging the feedback initial d-axis current within a certain time window. The DC output of the bias loop is injected into the first n beats of each cycle of the carrier in the form of harmonics. Without additional energy storage components, precise control of the frequency can be achieved.

[0056] S400: According to the time window, feedback the RMS value of the initial d-axis current, and output an effective DC voltage component through the RMS value loop;

[0057] In the above steps, the RMS value loop can be used to accurately control the amplitude of the current in real time for flexible and quantifiable injection current amplitude control. Specifically, the feedback of the RMS value of the initial d-axis current according to the time window and the output of the effective DC voltage component through the RMS value loop include:

[0058] S410: Calculate the sampling frequency according to the time window, and generate a number of sampling periods according to the sampling frequency;

[0059] In the above steps, as described above, the operations of the effective value loop and the above-mentioned bias loop need to be properly synchronized for accurate quantitative control. Therefore, the sampling frequency and the time window are set to be reciprocal to each other, which can be directly obtained according to the current frequency command. As an example, if the above time window is set to 100 Hz, the sampling frequency is set to 10 ms, that is, to ensure the correspondence between the operations of the effective value loop and the above-mentioned bias loop.

[0060] S420: Calculate the effective value of the initial d-axis current in each sampling period;

[0061] Specifically, calculating the effective value of the initial d-axis current in each sampling period includes: in any sampling period, square and sum the initial d-axis current values corresponding to each sampling point, then take the square root and average to obtain the effective value of the initial d-axis current. Specifically, the effective value can be calculated according to the following formula: where N is the sampling points in the sampling period, and i d is the initial d-axis current value corresponding to each sampling point.

[0062] S430: Receive the effective value command (RmsCmd), and generate an effective DC voltage component through a PI controller according to the effective values in each sampling period.

[0063] In the above steps, it also adopts receiving commands, PI control feedback, and controls according to the difference between the command and the feedback to generate an effective DC voltage component. This effective DC voltage component is a DC wave that fluctuates around a certain value. Calculate the feedback current effective value in real time and use this value for effective value loop control.

[0064] As a supplement, in order to make the operations of the bias loop and the effective value loop not interfere with each other, the bandwidth of the bias loop is set lower than the bandwidth of the effective value loop, so that the frequency ranges occupied by various different frequency components included in the bias loop and the effective value loop are different. Specifically, the bandwidth of the bias loop is much lower than that of the effective value loop.

[0065] S500: Generate the target d-axis voltage according to the product of the effective DC voltage component and the carrier wave of the injected DC bias wave to inject high-frequency alternating current for battery heating.

[0066] In the above steps, the DC component Ud output by the effective value loop is multiplied by the carrier wave to obtain the alternating current Ud, that is, the above-mentioned target d-axis voltage. The target d-axis voltage and the q-axis voltage obtained according to the q-axis current command are subjected to inverse Park transformation to obtain the α and β-axis voltages, and then input to the SVM to control the injection of high-frequency alternating current to execute the battery heating process. In this embodiment, there is no additional energy storage component, and no BSW is involved. Through the above-mentioned effective value loop, the injection current amplitude can be flexibly and quantitatively controlled. By introducing the bias loop, the control is more stable, and high-precision injection frequency control can be achieved. The frequency can be smoothly changed in a wide range in real time (for reference, see Figure 3 , Figure 3 which is the curve graph of the output current generated for experimental verification of the battery heating method provided by this embodiment. The frequency control is accurate, the frequency switching is smooth, the current is stable and controllable during switching, the current control is stable, and there is no overshoot in the step). Thus, the accurate control of the amplitude and frequency of the battery heating process is realized, and the battery heating efficiency is improved. In addition, a tooth-by-tooth current can be added to the q-axis to avoid mechanical vibration, and key information such as motor speed, heating current, and motor temperature can be monitored in real time to improve safety.

[0067] Embodiment 2: The present invention also provides a power battery heating device 6, including:

[0068] A receiving module 61, configured to receive a battery heating instruction, generate a d-axis current command and a q-axis current command, where the q-axis current command is used to output a q-axis current with a value of zero; and obtain an initial d-axis current according to the d-axis current command;

[0069] Specifically, controlling the q-axis current output to zero is mainly used to limit the rotation of the motor, so that after injecting high-frequency current into the d-axis, the battery is heated. A tooth-by-tooth current can also be injected into the q-axis to eliminate the influence of the tooth gap and reduce the mechanical vibration of the motor.

[0070] A first processing module 62, configured to receive a current frequency command, adjust a time window, and generate a carrier wave including several cycles according to the current frequency command; output a DC bias wave of the initial d-axis current through a bias loop and inject it into a preset frequency in each cycle of the carrier wave;

[0071] Specifically, for the carrier wave generated according to the frequency given in the frequency command, a bias loop is added. The bias is obtained by averaging the feedback initial d-axis current within a certain time window. The DC output of the bias loop is injected into the first n beats of each cycle of the carrier wave in the form of harmonics. Without additional energy storage components, accurate control of the frequency can be achieved.

[0072] A second processing module 63, configured to feedback the effective value of the initial d-axis current according to the time window and output an effective DC voltage component through an effective value loop;

[0073] Specifically, the calculation of the effective value is obtained by taking the square root of the sum of the squares of the initial d-axis current values corresponding to each sampling point and then averaging, so as to obtain the effective value of the initial d-axis current, which enables flexible and quantifiable control of the injected current amplitude.

[0074] The execution module 64 is configured to generate a target d-axis voltage according to the product of the effective DC voltage component and the carrier wave of the injected DC bias wave, so as to inject a high-frequency alternating current for battery heating.

[0075] In the above module, the DC Ud component output by the effective value loop is multiplied by the carrier wave to obtain the alternating current Ud, and through transformation, a high-frequency alternating target d-axis current is generated for battery heating.

[0076] In this embodiment, the receiving module receives a heating instruction, and through transformation, obtains the initial d-axis current and the initial q-axis current. The initial q-axis current outputs a (target) q-axis current with a value of zero through PI control. Based on the initial d-axis current, a carrier wave is generated according to the current frequency instruction in the first processing module. The bias loop obtains the bias by averaging the feedback Id within a certain time window. The DC output of the bias loop is injected into each cycle of the carrier wave in the form of harmonics. At the same time, the second processing module calculates the effective value of the feedback current in real time and uses this value for the current effective value loop control. Finally, in the execution module, a high-frequency alternating d-axis voltage is obtained according to the product of the effective DC voltage component and the carrier wave of the injected DC bias wave, and is injected into the circuit to achieve battery heating, accurately controlling the amplitude and frequency of the injected current during the battery heating process, with more stable control and higher heating efficiency.

[0077] Embodiment 3: The present invention further provides a power battery, which applies the power battery heating device described in Embodiment 2 above, and further includes other elements for enabling the power battery to work, so as to execute the power battery heating method described in Embodiment 1, achieving accurate control of the amplitude and frequency of the injected current during the battery heating process and improving the heating efficiency.

[0078] It should be noted that the embodiments of the present invention have good implementability and do not impose any form of limitation on the present invention. Any person skilled in the art may use the disclosed technical content to modify or transform it into an equivalent effective embodiment. However, as long as it does not depart from the technical solution of the present invention, any modification, equivalent change or modification made to the above embodiments based on the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for heating a power battery, characterized in that, Comprising: Receiving a battery heating instruction, generating a d-axis current instruction and a q-axis current instruction, wherein the q-axis current instruction is used to output a q-axis current with a value of zero; obtaining an initial d-axis current according to the d-axis current instruction; Receiving a current frequency instruction, adjusting a time window, and generating a carrier according to the current frequency instruction; Outputting a DC bias wave of the initial d-axis current through a bias loop, and injecting it into a preset frequency of the carrier; Feedbacking the effective value of the initial d-axis current according to the time window, and outputting an effective DC voltage component through an effective value loop; Based on the time window, keeping the bias loop and the effective value loop operationally synchronized; Generating a target d-axis voltage according to the product of the effective DC voltage component and the carrier injected with the DC bias wave, so as to inject a high-frequency alternating current for battery heating.

2. The battery heating method according to claim 1, wherein The outputting a DC bias wave of the initial d-axis current through a bias loop includes: Calculating a bias value of a sine wave formed by the initial d-axis current relative to a preset axis according to a time window; Receiving a bias instruction, and controlling the initial d-axis current according to the bias instruction and the bias value through a PI controller to output a bias with a value of zero, so as to obtain a DC bias wave.

3. The battery heating method according to claim 1, wherein The injecting into a preset frequency of the carrier includes: Superimposing the DC bias wave on an amplitude corresponding to a preset frequency in each period of the carrier to form a carrier injected with the DC bias wave.

4. The battery heating method according to claim 1, wherein The feedbacking the effective value of the initial d-axis current according to the time window, and outputting an effective DC voltage component through an effective value loop includes: Calculating a sampling frequency according to the time window, and generating a plurality of sampling periods according to the sampling frequency; Calculating the effective value of the initial d-axis current within each sampling period; Receiving an effective value instruction, and generating an effective DC voltage component through a PI controller according to the effective values within each sampling period.

5. The battery heating method according to claim 4, wherein The calculating the effective value of the initial d-axis current within each sampling period includes: For any sampling period, squaring and summing the initial d-axis current values corresponding to each sampling point, then taking the square root and averaging to obtain the effective value of the initial d-axis current.

6. The battery heating method according to claim 4, wherein: The sampling frequency and the time window are set to be reciprocal to each other.

7. The battery heating method according to claim 1, wherein Further comprising: Injecting a tooth-dependent current on the q-axis.

8. The battery heating method according to claim 1, characterized in that, Further comprising: Setting the bandwidth of the bias loop to be lower than the bandwidth of the effective value loop.

9. A power battery heating device, characterized in that, Comprising: A receiving module, configured to receive a battery heating instruction, generate a d-axis current instruction and a q-axis current instruction, wherein the q-axis current instruction is used to output a q-axis current with a value of zero; obtaining an initial d-axis current according to the d-axis current instruction; A first processing module, configured to receive a current frequency instruction, adjust a time window, and generate a carrier including a plurality of periods according to the current frequency instruction; outputting a DC bias wave of the initial d-axis current through a bias loop, and injecting it into a preset frequency in each period of the carrier; A second processing module, configured to feedback the effective value of the initial d-axis current according to the time window, output an effective DC voltage component through an effective value loop; keeping the bias loop and the effective value loop operationally synchronized based on the time window; An execution module, configured to generate a target d-axis voltage based on the product of the effective DC voltage component and the carrier wave of the injected DC bias wave, so as to inject a high-frequency alternating current for battery heating.

10. A power battery, characterized in that: The power battery heating device according to claim 9 above is applied.

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