Multiplexed quasi-resonant equalization circuit for series-parallel battery packs and control method thereof

Abstract

The application discloses a multiplex quasi-resonance equalization circuit for series-parallel connection battery pack and a control method thereof, and relates to the field of electrochemical energy storage. The circuit comprises a switch array and a quasi-resonance network, the switch array is arranged in correspondence with a battery string in the battery pack, and each battery string is connected to the multiplex quasi-resonance network through the corresponding switch array. The highest voltage difference between battery components (battery modules or battery monomers) in each battery string is sorted, and the driving signal of the switch array corresponding to the corresponding battery string is enabled in turn according to the size of the highest voltage difference, so that the voltage equalization of each battery string is realized through the multiplex quasi-resonance network. The application completes the voltage equalization of the series-parallel connection battery pack through the multiplex quasi-resonance network, and has important significance for the miniaturization and compact design of the series-parallel connection battery pack equalization circuit.

Description

Technical Field

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

[0002] With the introduction of the "dual carbon" goals and the construction of a new power system, my country's large-scale clean energy grid integration has posed new challenges to the safe and stable operation of the power system. Electrochemical energy storage, as a key technology and basic equipment for the power grid to cope with energy transition and improve system flexibility, has a large application scale and continues to develop rapidly. Lithium-ion batteries are often used as the primary energy storage and release carrier in electrochemical energy storage systems. However, the nominal voltage of a single lithium-ion battery cell is very low, and large numbers of battery cells are usually required to form high-voltage, high-power battery packs in series and parallel to meet the energy needs of applications such as wind and solar power output balancing on the source-grid-load side, peak and frequency regulation, and peak-valley arbitrage. Due to the limitations of the battery cell production process and the battery pack's operating environment, voltage imbalances can occur between battery cells during battery pack operation. This can cause individual cells to overcharge or over-discharge, affecting the performance and service life of the entire battery pack, and even causing safety accidents such as fire and explosion. Therefore, a voltage balancing circuit is required to balance and control the battery pack to ensure safe and efficient operation.

[0003] Based on the key components used in the balancing circuit, common lithium-ion battery voltage balancing circuits can be categorized into various types: resistive, capacitive, inductive, and transformer. Due to thermal management and energy loss issues during the balancing process, resistive balancing circuits have been gradually replaced by various active balancing circuits. Inductive balancing circuits offer high balancing currents, but their complex closed-loop control algorithms are a major drawback. Transformer balancing circuits offer fast balancing speeds, but the bulky magnetic components and low efficiency limit their development and application. Capacitive balancing circuits offer multiple advantages, such as fast balancing speed and the absence of closed-loop control, making them an ideal balancing solution. Quasi-resonant balancing circuits inherit the closed-loop control-free nature of capacitive balancing circuits and further enhance balancing speed and efficiency through zero-current switching.

[0004] However, the aforementioned balancing circuits are designed for a single battery string. For a battery pack consisting of multiple battery strings connected in parallel, a separate equalizer is required for each battery string. This solution exponentially increases the cost and size of the balancing circuit. Therefore, a new balancing circuit and control method for series-parallel battery packs is urgently needed to minimize the cost and size of the balancing circuit while ensuring its performance. 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 solutions:

[0007] In a first aspect, the present invention proposes a multiplexed quasi-resonant balancing circuit for series-parallel battery packs, 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 balancing between unbalanced battery components in each battery string.

[0008] 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.

[0009] 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 complementary to each other.

[0010] 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.

[0011] As a further improvement of the present invention, the quasi-resonant network includes a plurality of resonant units, each resonant unit includes two resonant cavities connected in series and two switching tubes, and each resonant cavity includes a resonant inductor and a resonant capacitor connected in series.

[0012] 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:

[0013] 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;

[0014] Setting a desired switching frequency, which should be less than the resonant frequency;

[0015] Estimate the resonant capacitor value based on the minimum voltage of all battery modules in the battery pack, the maximum voltage difference of the battery string, the equivalent resistance and the expected switching frequency;

[0016] 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 based on the resonant frequency;

[0017] According to the determined resonant capacitor and resonant inductor parameters, verify whether the quality factor is greater than or equal to 1. If it is satisfied, the parameter design of the resonant capacitor and resonant inductor is completed. If not, redesign the parameters;

[0018] The resonant capacitor satisfies:

[0019]

[0020] Where, 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;

[0021] The quality factor is:

[0022]

[0023] Where, R is the total parasitic resistance of the resonant unit, L is the resonant inductor, C is the resonant capacitor.

[0024] In a second aspect, the present invention proposes a method for controlling a multiplexed quasi-resonant balancing circuit for a series-parallel battery pack, which is based on the above-mentioned multiplexed quasi-resonant balancing circuit for a series-parallel battery pack and includes:

[0025] The voltage of all battery modules 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 corresponding switch arrays of the corresponding battery strings are enabled in sequence according to the magnitude of the maximum voltage difference of all battery strings, thereby balancing the voltage of each battery string in the battery pack.

[0026] 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 is achieved among all the battery components in the battery string.

[0027] 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:

[0028] Sort the highest voltage differences of all battery strings. 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.

[0029] 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;

[0030] When the driving signal of the battery string switch array corresponding to the maximum voltage difference is enabled, the driving signal of the next battery string switch array is reordered and enabled until the highest voltage difference of the battery string is less than the balancing start threshold, and then the voltage of each battery string in the battery pack is balanced in turn.

[0031] As a further improvement of the present invention, when the switch array corresponding to the battery string with the maximum voltage difference is driven, the quasi-resonant network continuously charges and discharges between the unbalanced battery components in the battery string until voltage balance is achieved among all battery components in the battery string, specifically including:

[0032] The driving signal for each switch array is a pair of complementary square wave signals with fixed periods and duty cycles. 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.

[0033] The quasi-resonant network continuously charges and discharges between the high-voltage and low-voltage battery components in the battery string until the maximum voltage difference of the battery string is less than the balancing start threshold, and the voltage balancing of the battery string is completed;

[0034] 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 balancing start threshold, the voltage balancing of the battery pack is completed.

[0035] 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:

[0036] The working state of each battery assembly in the battery string is controlled by two switching tubes, and the conversion of the charging and discharging state of the battery assembly is achieved by switching the on and off states of the two switching tubes;

[0037] 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;

[0038] 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;

[0039] 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.

[0040] The beneficial effects of the present invention are:

[0041] Existing balancing circuits can only achieve voltage balancing for a single battery string. For battery packs formed by connecting multiple battery strings in parallel, a separate equalizer is required for each battery string. The multiplexed balancing circuit proposed in this invention only requires a shared quasi-resonant network to achieve voltage balancing for all battery strings. By reusing the quasi-resonant network, the number of resonant capacitors and resonant inductors required for the battery pack is greatly reduced. This means that the balancing circuit proposed in this invention reduces hardware resource and cost requirements while maintaining excellent balancing performance, which is of great significance for reducing the size and cost of balancing circuits for series-parallel battery packs.

[0042] The balancing circuit proposed in this invention sequentially enables the drive signals of the corresponding switch arrays of the corresponding battery strings according to the highest voltage difference in the battery pack, thereby achieving voltage balancing for each battery string in the battery pack. This control method can accurately detect the operating status of each battery component in the battery pack and generate corresponding enable signals based on the degree of voltage imbalance among all battery strings, thereby making the battery pack voltage balancing more efficient and accurate, providing a strong guarantee for the safe and efficient operation of the battery pack.

[0043] The balancing circuit proposed in this invention, like existing quasi-resonant balancing circuits, uses a pair of complementary square wave signals with constant period and duty cycle to control the switch array corresponding to each battery string. This reduces the complexity of the control algorithm and eliminates the hardware required for closed-loop control, making the balancing circuit easier to implement. Furthermore, the balancing circuit proposed in this invention operates in a zero-current switching state, significantly reducing switching losses during the balancing process and increasing the balancing current of the balancing circuit. This enables the proposed balancing circuit to more efficiently and quickly improve voltage inconsistencies within the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0045] Figure 1 Schematic diagram of a multiplexed quasi-resonant balancing circuit for series-parallel battery strings in an embodiment of the present invention;

[0046] Figure 2 is a schematic diagram of various types of quasi-resonant networks in an embodiment of the present invention;

[0047] Figure 3 is a schematic diagram of driving signals for each switch array in an embodiment of the present invention;

[0048] Figure 4 is a schematic diagram of voltage balancing of a battery string through a quasi-resonant network in an embodiment of the present invention;

[0049] Figure 5 This is a flowchart of the highest voltage difference sorting and drive signal enabling of battery strings in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] 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 with reference to 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.

[0051] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings and specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0052] Example 1

[0053] 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.

[0054] Preferably, each battery string consists of n The battery pack is composed of a series of battery components, which are battery modules or battery cells; 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.

[0055] Preferably, the switch arrays are arranged in correspondence with the battery strings in the battery pack, and the number of switch arrays required for the battery pack equals the total number of parallel battery strings. The operating state of each battery module in the battery string is controlled by two switches, and the number of switches in the switch array corresponding to each battery string equals twice the number of series-connected battery modules in the battery string. All switches are N-channel MOSFETs of identical model and parameters.

[0056] Preferably, Figure 1 The quasi-resonant network in the embodiment uses a star structure as an example. The quasi-resonant network of the balancing circuit of the present invention can also be Figure 2There are many types of structures, including the classic structure, double-layer structure, chain structure, triangle structure, etc. In the quasi-resonant network, each resonant unit consists of two series-connected resonant cavities and two switching transistors. Each resonant cavity includes a series-connected resonant inductor and resonant capacitor. The parameters of all resonant inductors and resonant capacitors are the same.

[0057] Preferably, the resonant inductor in each resonant cavity L and resonant capacitance C The parameter optimization design includes the following steps:

[0058] 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:

[0059] R= 2 R ds(ON) + R C + R L

[0060] Where, 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.

[0061] Set the desired switching frequency f s , its value should be slightly smaller than the resonant frequency f r , the resonant frequency is:

[0062]

[0063]

[0064] 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 should satisfy:

[0065]

[0066] 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 based on the resonant frequency;

[0067] 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 not, the parameters need to be redesigned according to the above steps. Among them, the quality factor is:

[0068]

[0069] The multiplexed balancing circuit proposed in this embodiment requires only a single shared quasi-resonant network to achieve voltage balancing across all battery strings. Compared to existing balancing circuits, the balancing circuit proposed in this invention significantly reduces the number of quasi-resonant networks required for series-parallel battery packs by reusing quasi-resonant networks, while retaining the advantages of existing quasi-resonant balancing circuits, such as simple control, fast balancing speed, and high balancing efficiency. This achieves a miniaturized and compact design for series-parallel battery pack balancing circuits.

[0070] Example 2

[0071] like Figure 5 As shown, this embodiment proposes a control method for a multiplexed quasi-resonant balancing circuit 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:

[0072] 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 the order of magnitude, thereby performing voltage balancing for each battery string in the battery pack;

[0073] 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 is achieved among all the battery components in the battery string.

[0074] 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:

[0075] The maximum voltage difference between all battery stringsV di Sort by, if the maximum value of the highest voltage difference of all battery strings in the battery pack V dmax Less than the balancing start threshold V dth , then the balance is not started;

[0076] 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 pressure difference is enabled V dmax A driving signal corresponding to the battery string switch array;

[0077] When the maximum pressure difference V dmax When the driving signal of the corresponding battery string switch array is enabled, the maximum voltage difference of the battery string V dh Less than the balancing 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.

[0078] 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 voltage balance is achieved among all battery components in the battery string, specifically including:

[0079] 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 corresponding to the battery string with the maximum voltage difference is enabled, the battery string is voltage balanced through the quasi-resonant network.

[0080] 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 balancing start threshold V dth , the voltage balancing of the battery string is completed;

[0081] 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.

[0082] Preferably, Figure 4As shown in Figure 1, 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:

[0083] The working state of each battery assembly in the battery string is controlled by two switching tubes, and the conversion of the charging and discharging state of the battery assembly is achieved by switching the on and off states of the two switching tubes;

[0084] 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;

[0085] When the low voltage battery components in the battery string B k,i Corresponding switch tube S k,2j-1 and S k,2j-1 When conducting, the resonant cavity supplies the low voltage battery components B k,i Discharge, transferring energy to low-voltage battery components;

[0086] 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.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the 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 by 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 arrays are 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; 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 resonant cavity includes a resonant inductor and a resonant capacitor connected in series; The parameter design method of the resonant capacitor and the resonant inductor in the resonant cavity is: Estimating 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, which should be less than the resonant frequency; Estimate the resonant capacitor value based on the minimum voltage of all battery modules 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 based on the resonant frequency; According to the determined resonant capacitor and resonant inductor parameters, verify whether the quality factor is greater than or equal to 1. If it is satisfied, the parameter design of the resonant capacitor and resonant inductor is completed. If not, redesign the parameters; The resonant capacitor satisfies: Where, 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: Where, R is the total parasitic resistance of the resonant unit, L is the resonant inductor, C is the resonant capacitor.

2. The multiplexed quasi-resonant equalization circuit for series-parallel battery packs according to claim 1, characterized in that: The working status of each battery assembly in the battery string is controlled by two switching tubes. 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. The switching 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 complementary-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. A method for controlling a multiplexed quasi-resonant equalizing circuit for a series-parallel battery pack, the method being implemented based on the multiplexed quasi-resonant equalizing circuit for a series-parallel battery pack according to any one of claims 1 to 4, characterized in that: include: The voltage of all battery modules 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 corresponding switch arrays of the corresponding battery strings are enabled in sequence according to the magnitude of the maximum voltage difference of all battery strings, thereby balancing 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 is achieved among all the battery components in the battery string.

6. The method for controlling a multiplexed quasi-resonant equalization circuit for a series-parallel battery pack according to claim 5, wherein: The drive signals of the corresponding switch arrays of the corresponding battery strings are enabled in sequence according to the magnitude of the maximum voltage difference of all battery strings, specifically including: Sort the highest voltage differences of all battery strings. 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, the driving signal of the next battery string switch array is reordered and enabled until the highest voltage difference of the battery string is less than the balancing start threshold, and then the voltage of each battery string in the battery pack is balanced in turn.

7. The method for controlling a multiplexed quasi-resonant equalization circuit for a series-parallel battery pack according to claim 6, wherein: When the switch array corresponding to the battery string with the maximum voltage difference is driven, the quasi-resonant network continuously charges and discharges between the unbalanced battery modules in the battery string until the voltage is balanced among all battery modules in the battery string. Specifically, the following steps are performed: The driving signal for each switch array is a pair of complementary square wave signals with fixed periods and duty cycles. 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 maximum voltage difference of the battery string is less than the balancing start threshold, and 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 less than the balancing start threshold, the voltage balancing of the battery pack is completed.

8. The method for controlling a multiplexed quasi-resonant equalization circuit for a series-parallel battery pack according to claim 6, wherein: 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 switching tubes, and the conversion of the charging and discharging state of the battery assembly is achieved by switching the on and off states of the two switching 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.

Images