Multiplexing type quasi-resonance equalization circuit for series-parallel battery pack and control method thereof

Abstract

The invention discloses a multiplex quasi-resonance equalization circuit for a series-parallel battery pack and a control method thereof, and relates to the field of electrochemical energy storage. The circuit comprises switch arrays and a quasi-resonance network, the switch arrays are arranged corresponding to battery strings in a battery pack, and each battery string is connected to the multiplexed quasi-resonance network through the corresponding switch array. The maximum voltage difference between the battery assemblies (battery modules or battery monomers) in each battery string is sequenced, the driving signals of the switch arrays corresponding to the corresponding battery strings are enabled in sequence according to the maximum voltage difference, and then the voltage balance of each battery string is realized through the multiplexed quasi-resonance network. According to the invention, the voltage equalization of the series-parallel battery pack is completed through the multiplexed quasi-resonance network, and the circuit has important significance for the miniaturization and compact design of the equalization circuit of the series-parallel battery pack.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical energy storage, and in particular to a multiplexed quasi-resonant equalization circuit for series-parallel battery packs and a control method thereof. Background Art

[0002] With the proposal of the "dual carbon" goal and the construction of a new power system, my country's large-scale clean energy grid connection has put forward new challenges to the safe and stable operation of the power system. As an important technology and basic equipment for the power grid to cope with energy transformation and improve system flexibility, electrochemical energy storage has a huge application scale and is developing rapidly. Lithium ions are often used as the main energy storage and release carrier in electrochemical energy storage systems, but the nominal voltage of a single lithium-ion battery cell is very low. Usually, a large number of battery cells are required to be connected in series and parallel to form a high-voltage and high-power battery pack to meet the energy requirements of applications such as wind and solar output stabilization, peak and frequency regulation, and peak-valley arbitrage on the source-grid load side. Limited by the production process of battery cells and the use environment of the battery pack, voltage imbalance will occur between battery cells during the operation of the battery pack, which will cause individual battery cells to be overcharged or over-discharged, thereby affecting the working performance and service life of the entire battery pack, and even causing safety accidents such as fire and explosion of the battery pack. Therefore, it is necessary to use a voltage balancing circuit to balance and control the battery pack to ensure the safe and efficient operation of the battery pack.

[0003] According to the main components used in the balancing circuit, common lithium-ion battery voltage balancing circuits can be divided into multiple types such as resistive, capacitive, inductive and transformer types. Due to the thermal management and energy loss problems of resistive balancing circuits during the balancing process, they have been gradually replaced by various active balancing circuits. Inductive balancing circuits have large balancing currents, but the complex closed-loop control algorithm is the main disadvantage of this type of balancing circuit. Transformer balancing circuits have very fast balancing speeds, but the large size and low efficiency caused by bulky magnetic components limit their development and application. Capacitive balancing circuits have many advantages such as fast balancing speed and no need for closed-loop control, and are a more ideal balancing solution. Quasi-resonant balancing circuits inherit the capacitive balancing circuit without the need for closed-loop control, and further speed up the balancing speed and improve the balancing efficiency through zero current switching.

[0004] However, the above-mentioned balancing circuits are all for a single battery string. For a battery pack formed by connecting multiple battery strings in parallel, a separate balancing circuit needs to be configured for each battery string. This solution will increase the cost and volume of the balancing circuit exponentially. Therefore, it is urgent to propose a new balancing circuit and control method suitable for series-parallel battery packs, which can reduce the cost and volume as much as possible while ensuring the performance of the balancing circuit. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention aims to propose a multiplexed quasi-resonant balancing circuit for series-parallel battery packs and a control method thereof, so as to achieve a low-cost and miniaturized design of the series-parallel battery pack balancing circuit.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention proposes a multiplexed quasi-resonant balancing circuit for a series-parallel battery pack, comprising a switch array and a quasi-resonant network; the switch array is arranged corresponding to the battery strings in the battery pack, and each battery string is connected to the multiplexed quasi-resonant network through the corresponding switch array; the quasi-resonant network is used to achieve voltage balance between unbalanced battery components in each battery string. As a further improvement of the present invention, the working state of each battery assembly in the battery string is controlled by two switching tubes, and the number of switching tubes in the switch array corresponding to each battery string is equal to twice the number of series-connected battery assemblies in the battery string, and the switching tubes use N-channel MOSFETs with exactly the same model and parameters.

[0007] As a further improvement of the present invention, the switch array is controlled by a pair of complementary square wave signals with fixed periods and duty cycles, and two adjacent switch tubes in the switch array are complementarily turned on.

[0008] As a further improvement of the present invention, the quasi-resonant network adopts one of a star structure, a classical structure, a double-layer structure, a chain structure, and a triangle structure.

[0009] As a further improvement of the present invention, the quasi-resonant network includes a plurality of resonant units, each of which includes two resonant cavities connected in series and two switching tubes, and each of which includes a resonant inductor and a resonant capacitor connected in series.

[0010] As a further improvement of the present invention, the parameter design method of the resonant capacitor and the resonant inductor in the resonant cavity is: Estimate the equivalent resistance of each resonant unit; the equivalent resistance is calculated based on the total parasitic resistance of the resonant unit; the total parasitic resistance of the resonant unit is calculated based on the on-resistance of the switch tube, the parasitic resistance of the resonant capacitor, and the parasitic resistance of the resonant inductor; Setting a desired switching frequency, wherein the desired switching frequency should be less than the resonant frequency; Estimate the capacitance of the resonant capacitor based on the minimum voltage of all battery components in the battery pack, the maximum voltage difference of the battery string, the equivalent resistance and the expected switching frequency; Determine the specific type of MOSFET and resonant capacitor to meet the value conditions of the resonant capacitor, and determine the specific type of resonant inductor according to the resonant frequency; According to the determined parameters of the resonant capacitor and the resonant inductor, verify whether the quality factor is greater than or equal to 1. If it is satisfied, the parameter design of the resonant capacitor and the resonant inductor is completed. If it is not satisfied, redesign the parameters; The resonant capacitor satisfies:

[0011] In the formula, V Bmin is the minimum voltage of all battery components in the battery pack, ΔV Bmax is the maximum voltage difference of the battery string, R eq is the equivalent resistance of each resonant unit when the balancing circuit is working, f s is the desired switching frequency; The quality factor is:

[0012] In the formula, R is the total parasitic resistance of the resonant unit, L is the resonant inductor, C is the resonant capacitor.

[0013] In a second aspect, the present invention proposes a multiplexed quasi-resonant equalization circuit control method for a series-parallel battery pack, which is implemented based on the multiplexed quasi-resonant equalization circuit for a series-parallel battery pack, and includes: Collect the voltage of all battery components in the battery pack in real time, calculate the maximum voltage difference of all battery strings, enable the drive signal of the corresponding switch array of the corresponding battery string in sequence according to the magnitude of the maximum voltage difference of all battery strings, and then balance the voltage of each battery string in the battery pack; When the switch array of the battery string corresponding to the maximum voltage difference is driven, the quasi-resonant network will continuously charge and discharge between the unbalanced battery components in the battery string until the voltage balance among all the battery components in the battery string is achieved.

[0014] As a further improvement of the present invention, the driving signals of the switch arrays corresponding to the corresponding battery strings are enabled in sequence according to the magnitude of the maximum voltage difference of all battery strings, specifically including: The highest voltage differences of all battery strings are sorted. If the maximum value of the highest voltage differences of all battery strings in the battery pack is less than the balancing start threshold, balancing will not be started. If the maximum value of the highest voltage difference of all battery strings in the battery pack is greater than or equal to the balancing start threshold, the driving signal of the switch array of the battery string corresponding to the maximum voltage difference is enabled; When the driving signal of the battery string switch array corresponding to the maximum voltage difference is enabled, until the highest voltage difference of the battery string is less than the balancing start threshold, the driving signal of the next battery string switch array is reordered to enable the voltage balancing of each battery string in the battery pack in turn.

[0015] As a further improvement of the present invention, when the switch array of the battery string corresponding to the maximum voltage difference is driven, the quasi-resonant network continuously charges and discharges between the unbalanced battery components in the battery string until the voltage balance among all the battery components in the battery string is achieved, specifically including: The driving signal of each switch array is a pair of complementary square wave signals with fixed period and duty cycle. When the driving signal of the switch array corresponding to the battery string with the maximum voltage difference is enabled, the battery string is voltage-balanced through the quasi-resonant network. The quasi-resonant network continuously charges and discharges between the high-voltage and low-voltage battery components in the battery string until the highest voltage difference of the battery string is less than the equalization start threshold, and the voltage equalization of the battery string is completed; The voltage of each battery string in the battery pack is balanced in turn. When the highest voltage difference of all battery strings is less than the balance start threshold, the voltage balance of the battery pack is completed.

[0016] As a further improvement of the present invention, the quasi-resonant network continuously charges and discharges between the high-voltage battery assembly and the low-voltage battery assembly in the battery string, specifically including: The working state of each battery assembly in the battery string is controlled by two switch tubes, and the conversion of the charging and discharging state of the battery assembly is realized by switching the on and off states of the two switch tubes; When the switch tube corresponding to the high-voltage battery assembly in the battery string is turned on, the high-voltage battery assembly charges the resonant cavity and transfers energy to the resonant cavity; When the switch tube corresponding to the low-voltage battery assembly in the battery string is turned on, the resonant cavity discharges the low-voltage battery assembly and transfers energy to the low-voltage battery assembly; By continuously switching between the two working states of the resonant cavity, the energy of the high-voltage battery assembly is transferred to the low-voltage battery assembly, ultimately achieving voltage balance between the battery assemblies in the battery string.

[0017] The beneficial effects of the present invention are: The existing equalization circuit can only achieve voltage equalization of a single battery string. For a battery pack formed by connecting multiple battery strings in parallel, a separate equalizer needs to be configured for each battery string. The multiplexed equalization circuit proposed in the present invention only needs a common quasi-resonant network to achieve voltage equalization of all battery strings. Through the reuse of the quasi-resonant network, the number of resonant capacitors and resonant inductors required for the battery pack is greatly reduced. This means that the equalization circuit proposed in the present invention reduces hardware resources and cost requirements while ensuring excellent equalization performance, which is of great significance to reducing the volume and cost of the equalization circuit of the series-parallel battery pack.

[0018] The balancing circuit proposed in the present invention enables the driving signals of the corresponding switch arrays of the corresponding battery strings in sequence according to the highest voltage difference of the battery strings in the battery pack, thereby realizing voltage balancing of each battery string in the battery pack. This control method can accurately detect the working status of each battery component in the battery pack, and generate corresponding enabling signals according to the voltage imbalance degree of all battery strings, so that the voltage balancing of the battery pack is more efficient and accurate, providing a strong guarantee for the safe and efficient operation of the battery pack.

[0019] The balancing circuit proposed in the present invention is the same as the existing quasi-resonant balancing circuit, and the switch array corresponding to each battery string is controlled by a pair of complementary square wave signals with constant period and duty cycle, which reduces the complexity of the control algorithm and eliminates the hardware conditions required for closed-loop control, making the balancing circuit easier to implement. In addition, the balancing circuit proposed in the present invention operates in a zero-current switching state, which greatly reduces the switching loss during the balancing process and increases the balancing current of the balancing circuit, so that the proposed balancing circuit can improve the voltage inconsistency in the battery pack more efficiently and quickly. BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a schematic diagram of a multiplexed quasi-resonant equalization circuit for series-parallel battery strings in an embodiment of the present invention; Figure 2 is a schematic diagram of various types of quasi-resonant networks in an embodiment of the present invention; Figure 3 is a schematic diagram of a driving signal of each switch array in an embodiment of the present invention; Figure 4 is a schematic diagram of voltage equalization of a battery string through a quasi-resonant network in an embodiment of the present invention; Figure 5 It is a flowchart of the highest voltage difference sorting and driving signal enabling of battery strings in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, wherein the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0023] Embodiment 1 like Figure 1 As shown, this embodiment proposes a multiplexed quasi-resonant balancing circuit for series-parallel battery packs, including a switch array and a quasi-resonant network.

[0024] Preferably, each battery string consists of n The battery pack is composed of battery components connected in series, and the battery components are battery modules or battery monomers; the battery pack is composed of m The switch array is set corresponding to the battery string in the battery pack, and each battery string is connected to the multiplexed quasi-resonant network through the corresponding switch array. n The resonant cavity is used to achieve voltage balance between unbalanced battery components in each battery string.

[0025] Preferably, the switch arrays are arranged corresponding to the battery strings in the battery pack, and the number of switch arrays required for the battery pack is equal to the total number of parallel battery strings. The working state of each battery assembly in the battery string is controlled by two switch tubes, and the number of switch tubes in the switch array corresponding to each battery string is equal to twice the number of series battery assemblies in the battery string. All switch tubes use N-channel MOSFETs with exactly the same model and parameters.

[0026] Preferably, Figure 1 The quasi-resonant network in the embodiment uses a star structure as an example. The quasi-resonant network of the equalization circuit of the present invention can also be Figure 2 There are many types of structures, such as the classic structure, double-layer structure, chain structure, triangle structure, etc. shown in the figure. Each resonant unit in the quasi-resonant network includes two series-connected resonant cavities and two switching tubes. Each resonant cavity includes a series-connected resonant inductor and a resonant capacitor. The parameters of all resonant inductors and resonant capacitors are the same.

[0027] Preferably, the resonant inductor in each resonant cavity L and resonant capacitor C The parameter optimization design includes the following steps: Estimate the equivalent resistance of each resonant unit R eq , which is approximately the total parasitic resistance of the resonant unit R 5 times, the total parasitic resistance is: R= 2 R ds(ON) + R C + R L In the formula, R ds(ON) , R C , R L They are the on-resistance of MOSFET, the parasitic resistance of resonant capacitor and the parasitic resistance of resonant inductor respectively.

[0028] Set the desired switching frequency f s , its value should be slightly less than the resonant frequency f r , the resonant frequency is:

[0029]

[0030] Based on the minimum voltage of all battery components in the battery pack V Bmin The maximum voltage difference between all battery strings ΔV Bmax , combined with the equivalent resistance R eq and switching frequency f s The resonant capacitance can be roughly estimated C The value of the resonant capacitor C The value of should satisfy:

[0031] Determine the specific type of MOSFET and resonant capacitor to meet the value conditions of the resonant capacitor, and determine the specific type of resonant inductor according to the resonant frequency; Verify the quality factor based on the determined resonant capacitor and resonant inductor parameters Q Is it greater than or equal to 1? If it is satisfied, the parameter design is completed. If it is not satisfied, the parameters need to be redesigned according to the above steps. Among them, the quality factor is:

[0032] The multiplexed balancing circuit proposed in this embodiment only needs one common quasi-resonant network to achieve voltage balancing of all battery strings. Compared with the existing balancing circuit, the balancing circuit proposed in the present invention greatly reduces the number of quasi-resonant networks required for the series-parallel battery pack through the reuse of quasi-resonant networks, but inherits the advantages of the existing quasi-resonant balancing circuit, such as simple control, fast balancing speed, and high balancing efficiency. The miniaturization and compact design of the series-parallel battery pack balancing circuit is realized.

[0033] Embodiment 2 like Figure 5 As shown, this embodiment proposes a multiplexed quasi-resonant balancing circuit control method for a series-parallel battery pack, using the multiplexed quasi-resonant balancing circuit for a series-parallel battery pack, the topology of the balancing circuit is as follows Figure 1 The method includes: Real-time acquisition of the voltage of all battery components in the battery pack V Bi,j , and calculate the maximum voltage difference of all battery strings V di , based on the highest voltage difference of all battery strings V di The driving signals of the switch arrays corresponding to the corresponding battery strings are enabled in order of magnitude, thereby performing voltage balancing for each battery string in the battery pack; When the maximum pressure difference V dmax When the switch array of the corresponding battery string is driven, the quasi-resonant network will continuously charge and discharge between the unbalanced battery components in the battery string until the voltage balance among all the battery components in the battery string is achieved.

[0034] Preferably, the driving signals of the switch arrays corresponding to the corresponding battery strings are enabled in sequence according to the magnitude of the maximum voltage differences of all battery strings, specifically including: Maximum voltage difference for all battery strings V di Sorting, if the maximum value of the highest voltage difference of all battery strings in the battery pack V dmax Less than the balance start threshold V dth , then the balance is not started; If the maximum value of the highest voltage difference of all battery strings in the battery pack V dmax Greater than or equal to the balancing start threshold V dth , then the maximum voltage difference is enabled V dmax A driving signal corresponding to the battery string switch array; When the maximum pressure difference V dmaxWhen the driving signal of the corresponding battery string switch array is enabled, until the maximum voltage difference of the battery string V dh Less than the balance start threshold V dth After that, the drive signal of the next battery string switch array is reordered to enable, and then the voltage of each battery string in the battery pack is balanced in turn.

[0035] Preferably, when the switch array of the battery string corresponding to the maximum voltage difference is driven, the quasi-resonant network continuously charges and discharges between the unbalanced battery components in the battery string until the voltage balance among all the battery components in the battery string is achieved, specifically including: like Figure 3 As shown, the driving signal of each switch array is a pair of complementary square wave signals with fixed period and duty cycle. When the driving signal of the switch array of the battery string corresponding to the maximum voltage difference is enabled, the battery string is voltage balanced through the quasi-resonant network. The quasi-resonant network continuously charges and discharges between the high-voltage battery components and the low-voltage battery components in the battery string until the maximum voltage difference of the battery string is reached. V dh Less than the balance start threshold V dth , the voltage balancing of the battery string is completed; The voltage of each battery string in the battery pack is balanced in turn. When the highest voltage difference of all battery strings is V di Both are less than the balance start threshold V dth , the voltage balancing of the battery pack is completed.

[0036] Preferably, Figure 4 As shown, the quasi-resonant network continuously charges and discharges between the high-voltage battery components and the low-voltage battery components in the battery string, specifically including: The working state of each battery assembly in the battery string is controlled by two switch tubes, and the conversion of the charging and discharging state of the battery assembly is realized by switching the on and off states of the two switch tubes; When the high voltage battery components in the battery string B k,j Corresponding switch tube S k,2j and S k,2j When conducting, the high voltage battery assembly B k,j Charge the resonant cavity and transfer energy into it; When the battery string has low voltage battery components B k,i Corresponding switch tube S k,2j-1 and Sk,2j-1 When turned on, the resonant cavity provides power to the low-voltage battery assembly. B k,i Discharge, transferring energy to low-voltage battery components; By continuously switching between the two working states of the resonant cavity, the energy of the high-voltage battery assembly is transferred to the low-voltage battery assembly, ultimately achieving voltage balance between the battery assemblies in the battery string.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A multiplexed quasi-resonant equalization circuit for series-parallel battery packs, characterized in that: including switch arrays and quasi-resonant networks; The switch array is arranged corresponding to the battery strings in the battery pack, and each battery string is connected to the multiplexed quasi-resonant network through the corresponding switch array; The quasi-resonant network is used to achieve voltage balance between unbalanced battery components in each battery string.

2. The multiplexed quasi-resonant equalization circuit for series-parallel battery packs according to claim 1, characterized in that: The working state of each battery assembly in the battery string is controlled by two switch tubes. The number of switch tubes in the switch array corresponding to each battery string is equal to twice the number of series-connected battery assemblies in the battery string. The switch tubes use N-channel MOSFETs with exactly the same model and parameters.

3. The multiplexed quasi-resonant equalization circuit for series-parallel battery packs according to claim 2, characterized in that: The switch array is controlled by a pair of complementary square wave signals with fixed periods and duty cycles, and two adjacent switch tubes in the switch array are complementarily turned on.

4. The multiplexed quasi-resonant equalization circuit for series-parallel battery packs according to claim 1, characterized in that: The quasi-resonant network adopts one of a star structure, a classical structure, a double-layer structure, a chain structure, and a triangle structure.

5. The multiplexed quasi-resonant equalization circuit for series-parallel battery packs according to claim 4, characterized in that: The quasi-resonant network includes a plurality of resonant units, each of which includes two resonant cavities connected in series and two switch tubes, and each of which includes a resonant inductor and a resonant capacitor connected in series.

6. The multiplexed quasi-resonant equalization circuit for series-parallel battery packs according to claim 5, characterized in that: The parameter design method of the resonant capacitor and the resonant inductor in the resonant cavity is: Estimating an equivalent resistance of each resonant unit; the equivalent resistance is calculated based on the total parasitic resistance of the resonant unit; The total parasitic resistance of the resonant unit is calculated according to the on-resistance of the switch tube, the parasitic resistance of the resonant capacitor, and the parasitic resistance of the resonant inductor; Setting a desired switching frequency, wherein the desired switching frequency should be less than the resonant frequency; Estimate the capacitance of the resonant capacitor based on the minimum voltage of all battery components in the battery pack, the maximum voltage difference of the battery string, the equivalent resistance and the expected switching frequency; Determine the specific type of MOSFET and resonant capacitor to meet the value conditions of the resonant capacitor, and determine the specific type of resonant inductor according to the resonant frequency; According to the determined parameters of the resonant capacitor and the resonant inductor, verify whether the quality factor is greater than or equal to 1. If it is satisfied, the parameter design of the resonant capacitor and the resonant inductor is completed. If it is not satisfied, redesign the parameters; The resonant capacitor satisfies: In the formula, V Bmin is the minimum voltage of all battery components in the battery pack, ΔV Bmax is the maximum voltage difference of the battery string, R eq is the equivalent resistance of each resonant unit when the balancing circuit is working, f s is the desired switching frequency; The quality factor is: In the formula, R is the total parasitic resistance of the resonant unit, L is the resonant inductor, C is the resonant capacitor.

7. A control method for a multiplexed quasi-resonant equalization circuit for a series-parallel battery pack, based on the multiplexed quasi-resonant equalization circuit for a series-parallel battery pack according to any one of claims 1 to 6, characterized in that: include: The voltage of all battery components in the battery pack is collected in real time, and the maximum voltage difference of all battery strings is calculated. The driving signals of the switch arrays corresponding to the corresponding battery strings are enabled in sequence according to the magnitude of the maximum voltage difference of all battery strings, so as to balance the voltage of each battery string in the battery pack. When the switch array of the battery string corresponding to the maximum voltage difference is driven, the quasi-resonant network will continuously charge and discharge between the unbalanced battery components in the battery string until the voltage balance among all the battery components in the battery string is achieved.

8. The method for controlling a multiplexed quasi-resonant equalization circuit for a series-parallel battery pack according to claim 7, characterized in that: The driving signals of the switch arrays corresponding to the corresponding battery strings are enabled in sequence according to the magnitude of the maximum voltage difference of all battery strings, specifically including: The highest voltage differences of all battery strings are sorted. If the maximum value of the highest voltage differences of all battery strings in the battery pack is less than the balancing start threshold, balancing will not be started. If the maximum value of the highest voltage difference of all battery strings in the battery pack is greater than or equal to the balancing start threshold, the driving signal of the switch array of the battery string corresponding to the maximum voltage difference is enabled; When the driving signal of the battery string switch array corresponding to the maximum voltage difference is enabled, until the highest voltage difference of the battery string is less than the balancing start threshold, the driving signal of the next battery string switch array is reordered to enable the voltage balancing of each battery string in the battery pack in turn.

9. The multiplexed quasi-resonant equalization circuit control method for series-parallel battery packs according to claim 8, characterized in that: When the switch array of the battery string corresponding to the maximum voltage difference is driven, the quasi-resonant network continuously charges and discharges between the unbalanced battery components in the battery string until the voltage balance among all battery components in the battery string is achieved, specifically including: The driving signal of each switch array is a pair of complementary square wave signals with fixed period and duty cycle. When the driving signal of the switch array corresponding to the battery string with the maximum voltage difference is enabled, the battery string is voltage-balanced through the quasi-resonant network. The quasi-resonant network continuously charges and discharges between the high-voltage battery assembly and the low-voltage battery assembly in the battery string until the highest voltage difference of the battery string is less than the equalization start threshold, and the voltage equalization of the battery string is completed; The voltage of each battery string in the battery pack is balanced in turn. When the highest voltage difference of all battery strings is less than the balance start threshold, the voltage balance of the battery pack is completed.

10. The multiplexed quasi-resonant equalization circuit control method for series-parallel battery packs according to claim 8, characterized in that: The quasi-resonant network continuously charges and discharges between the high-voltage battery components and the low-voltage battery components in the battery string, including: The working state of each battery assembly in the battery string is controlled by two switch tubes, and the conversion of the charging and discharging state of the battery assembly is realized by switching the on and off states of the two switch tubes; When the switch tube corresponding to the high-voltage battery assembly in the battery string is turned on, the high-voltage battery assembly charges the resonant cavity and transfers energy to the resonant cavity; When the switch tube corresponding to the low-voltage battery assembly in the battery string is turned on, the resonant cavity discharges the low-voltage battery assembly and transfers energy to the low-voltage battery assembly; By continuously switching between the two working states of the resonant cavity, the energy of the high-voltage battery assembly is transferred to the low-voltage battery assembly, ultimately achieving voltage balance between the battery assemblies in the battery string.

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