CN111817374B - Decoupling type modularized active equalization circuit and strategy applied to lithium battery pack - Google Patents

Abstract

The invention discloses a decoupling type modularized active equalization circuit and strategy applied to a lithium battery pack. The traditional direct modularized active equalization has the advantages that due to the coupling effect in the modules and among the modules, certain single batteries can generate equalization overlapping phenomenon, the electric quantity required to be transferred for active equalization is additionally increased, the equalization rate and the equalization efficiency are reduced, and the battery circulation is increased. According to the decoupling modular active equalization method provided by the invention, the inter-module equalization lines are connected with the equalization buses of the modules, so that the coupling between the modules is eliminated, the phenomenon of equalization overlapping of single batteries is avoided, and the equalization rate and the equalization efficiency are improved. In addition, the invention provides an equalization strategy which is suitable for an equalization circuit, and simulation results show that the equalization method can effectively avoid the phenomenon of equalization overlapping while guaranteeing the equalization rate and the efficiency.

Description

Decoupling type modularized active equalization circuit and strategy applied to lithium battery pack

Technical Field

The invention relates to the field of lithium batteries, in particular to a decoupling type modularized active equalization circuit and strategy applied to a lithium battery pack.

Background

The lithium battery has the advantages of high energy density, long service life, low self-discharge rate, no memory effect and the like, and is widely applied to the energy storage field. However, at present, the voltage of the lithium ion single battery is about 3.7V, so that tens or even hundreds of single batteries are required to be connected in series to form a battery pack in order to achieve higher voltage, and the parameters of the single batteries are inconsistent due to different chemical and electrical characteristics of the batteries in the manufacturing and production processes. In addition, different environmental temperatures and uneven degradation after aging can also cause inconsistent parameters of each single battery. The problems cause that after a plurality of times of cyclic charge and discharge operations, larger electric quantity inconsistency exists among the single batteries, and the available energy and the service life of the battery pack are reduced.

The energy of the high-SOC (State of Charge) single battery can be transferred to the low-SOC single battery through the battery active equalization technology, the influence of inconsistent battery parameters is weakened or even eliminated, the available capacity of the battery pack is improved, and the service life of the battery pack is prolonged. However, the balance power and the balance efficiency are affected, and in a large-scale lithium battery pack, the battery pack needs to be equally divided into a plurality of battery modules, and the balance between the modules is performed in each module so as to improve the overall balance rate. However, the existing direct modularized equalization method has the coupling effect of in-module equalization and inter-module equalization, generates equalization overlapping phenomenon, reduces equalization power and equalization efficiency, and causes repeated charge and discharge of the battery to increase battery aging.

Fig. 1 is a schematic diagram of direct modularized active equalization, which consists of module units and an inter-module equalization circuit. Where N is the number of cells in each module, M is the number of modules, subscript i (i=1, 2,3 … N) is the cell index, and subscript j (j=1, 2,3 … M) is the module unit index. The module unit comprises a first module, a second module and a third module … M-th module, wherein M groups of modules are the same; each module is connected through an inter-module equalization circuit to realize inter-module equalization. Wherein, the single battery inside each module can realize the internal balance, and each module as a whole realizes the balance among the modules through the balance circuit among the modules.

For the convenience of explaining the equalization overlap phenomenon generated by the direct modularized active equalization, it is assumed that two groups of modules, namely, the module 1 and the module 2, exist in the battery pack and no energy loss occurs when the equalization is performed, as shown in fig. 2. The module 1 comprises three single batteries C with the same type _1,1 、C _2,1 、C _3,1 The SOC is 90%, 80% and 70% respectively, and is equal to the average SOC of three single batteries when the three single batteries reach an equilibrium state in the module _a1 I.e. SOC _a1 80%. The module 2 comprises three single batteries C with the same model as the module 1 _1,2 、C _2,2 、C _3,2 The SOC of the three single batteries is 70%, 30% and 20% respectively, and the three single batteries are in the dieAverage SOC when an equilibrium state is reached within a block _a2 40%. Average SOC when 6 single batteries in two groups of modules reach equilibrium state _a 60%.

The two modules are directly modularized and actively balanced, and the balancing can be divided into two stages:

stage one: from state 1 to state 2, this stage performs intra-module equalization on both modules. The state 1 is the initial state that the single batteries in the two modules are unbalanced, and the single battery C with the highest SOC in the module 1 _1,1 Transferring electric quantity to single battery C with lowest SOC _3,1 When the SOC of the three single batteries reaches the SOC _a1 80% of the time, the intra-module equalization of module 1 is stopped. Single battery C with highest SOC in module 2 _1,2 Transferring electric quantity to low SOC single battery C _2,2 And C _3,2 When the SOC of the three single batteries reaches the SOC _a2 40% of the time, the intra-module equalization of module 2 is stopped.

The value of the length of the rectangular bottom edge of each state diagram representing the single battery SOC is equal to the value of the charge quantity Q of the full state of one single battery, so the value of the area of the released electric quantity in the state diagram can be regarded as the value of the corresponding single battery released electric quantity.

The amount of charge transferred inside the module 1 is equal to the area S ₁ The magnitude of the charge transferred inside the module 2 is equal to the area S ₃ Size of the product.

Stage two: from state 2 to state 3, the second phase performs inter-module equalization on both modules. The direct modularized equalization is to take the whole module as a whole to perform inter-module equalization, so that the electric quantity of the single batteries in the module can be uniformly increased or reduced. The single cells in the module 1 uniformly transfer energy to the single cells in the module 2, because the single cells are identical in model number and connected in series, and when the states of charge of the six single cells in the two modules reach the SOC without considering the balanced energy loss _a At 60%, inter-module equalization is stopped. At this time, all the single batteries in the two modules reach an equilibrium state, and the equilibrium operation is stopped.

Co-transfer of Module 1 to Module 2 3S ₂ The amount of charge in the area.

The analysis shows that the phase one and phase two co-transfer charge quantity Q _ec ＝S ₁ +3S ₂ +S ₃ =q. Wherein the single cells C in the module 1 _3,1 Charging S in the first stage ₁ A charge amount of a magnitude of S is released in the second stage ₂ The charge quantity is equal to that of the single battery C, and the phenomenon of repeated charge and discharge is called balanced overlap phenomenon _3,1 The electric quantity is reduced from 70% to 60%, namely, 0.1Q charge is transferred, and 0.3Q charge is actually transferred, wherein 0.2Q charge repeatedly transferred is the overlapped transferred charge Q _er1 Such overlapping transfer loses part of the power of the equalization circuit, and increases the power loss due to equalization, and the repeated charge and discharge of the single cells overlapping in equalization occurs, resulting in a reduction in battery life. Wherein the single cells C in the module 2 _1,2 In the first stage release S ₃ A charge amount of a magnitude of S is charged in the second stage ₂ The equalizing and overlapping phenomenon also occurs for the electric charge quantity of the magnitude, and the equalizing and overlapping electric charge quantity Q _er2 At 0.2Q, the overlapped charge quantity Q is balanced in two stages _er ＝Q _er1 +Q _er2 ＝0.3Q。

If the average state of charge SOC of each single battery in one module _aj Greater than SOC _a The in-module SOC is lower than the SOC _aj The cell stack phenomenon of the battery can occur. If the average state of charge SOC of each single battery in one module _aj Less than SOC _a The in-module SOC is higher than the SOC _aj The cell stack phenomenon of the battery can occur.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a decoupling type modularized active equalization circuit and strategy which are applied to a lithium battery pack, and which are used for eliminating the coupling effect of modularized equalization in a module and among modules, eliminating the equalization overlapping phenomenon and avoiding repeated charge and discharge of single batteries caused by equalization overlapping.

The aim of the invention is realized by the following technical scheme: a decoupling type modularized active equalization circuit applied to a lithium battery pack comprises M groups of module units with the same structure and an inter-module equalization circuit;

each module unit comprises a battery pack and an in-module equalization circuit; the battery pack is formed by connecting N single batteries in series;

the in-module equalizing circuit comprises a group of in-module switching tube arrays, a group of control switching tubes and a group of in-module equalizing inductors;

the in-module switching tube array comprises 2N+2 in-module switching tubes: one end of the switch tube in the 2i-1 th module and one end of the switch tube in the 2 i-th module are respectively connected with the positive electrode of the i-th single battery, wherein i=1, 2, … and N; one end of the 2N+1-th in-module switching tube is connected with the negative electrode of the N-th single battery;

the other end of the switching tube in the 2i-1 th module is connected to form a first equalizing bus, and the other end of the switching tube in the 2 i-th module is connected to form a second equalizing bus, i=1, 2, … and n+1;

one end of the control switch tube is connected with the first equalizing bus, the other end of the control switch tube is connected with one end of the equalizing inductance in the module, and the other end of the equalizing inductance in the module is connected with the second equalizing bus;

The inter-module balancing circuit comprises a group of inter-module switching tube arrays and inter-module balancing inductors;

the inter-module switching tube array comprises 2M inter-module switching tubes: one end of the switching tube between the 2j-1 th modules is connected with a first equalizing bus of each j-th module, and the other end of the switching tube between the 2j-1 th modules is connected to form a first equalizing bus between the modules; one end of the switching tube between the second modules is connected with a second equalizing bus of the second module, and the other end of the switching tube between the second modules is connected with the second equalizing bus of the second module; j=1, 2, …, M;

and two ends of the inter-module balance inductor are respectively connected with the first inter-module balance bus and the second inter-module balance bus.

Further, the switch tube in the module is composed of two bidirectional switch tubes formed by connecting two NMOS tube sources with the same type in series. The control switch tube is composed of two bidirectional switch tubes formed by connecting source electrodes of NMOS tubes with the same type in series. The inter-module switching tube is composed of two bi-directional switching tubes formed by connecting source electrodes of NMOS tubes of the same type in series.

Further, the battery packs of the M groups of module units are connected in series.

Another object of the present invention is to provide a decoupling type modular active equalization strategy applied to a lithium battery pack, comprising the steps of:

S1, the MCU collects the voltage of each single battery in the current series battery pack and carries out SOC estimation;

s2, calculating the SOC range delta SOC of each single battery;

s3, judging whether the extremely poor delta SOC is greater than or equal to the equilibrium preset value delta SOC _th If yes, the single battery is in an unbalanced state, and the balancing operation is needed to be carried out, and S4 is executed; otherwise, the single battery is in an equilibrium state, and the equilibrium operation is not needed, and the step S4 is executed;

s4, ending the operation;

s5, calculating the average value of the SOC of all the single batteries, and recording the average value as the SOC _a ；

S6, calculating the following data of each module:

a. average SOC: i.e. the average SOC of all the single batteries in each module, the average SOC of the jth module is recorded as SOC _a,j ；

b、SOC _a,j Is denoted as delta SOC _m ；

c. Extremely poor delta SOC of each single battery SOC in jth module _j ；

d. Calculating the in-module SOC of the j-th module _i,j Greater than SOC _a Number h of unit cells of (2) _j And less than SOC _a Number of unit cells l _j ；

e. For SOC _aj Greater than SOC _a The module of (2) calculates that the electric quantity is smaller than the SOC _a SOC of a single battery of (a) _i,j And SOC (System on chip) _a Sum of absolute value of difference SOC _tj The method comprises the steps of carrying out a first treatment on the surface of the For SOC _aj Less than SOC _a The module of (1) calculates that the electric quantity is larger than the SOC _a SOC of a single battery of (a) _i,j And SOC (System on chip) _a Sum of absolute value of difference SOC _tj ；

S7, an active equalization system controller performs inter-module equalization operation after processing the SOC of each single battery;

s8, the active equalization system controller executes the in-module equalization operation after processing the SOC of each single battery.

Further, the step S7 includes the following substeps:

s71, judging whether the maximum value of the average SOC difference values of all the modules exceeds the preset value delta SOC of the inter-module equalization _thm If yes, it is indicated that the imbalance between the modules is too large, and the balancing operation between the modules is needed, and S731 is executed; otherwise, the battery modules are in an equilibrium state, and S72 is executed;

s72, not executing the inter-module equalization and ending the operation;

s73, the arrangement condition of each single battery SOC in the module influences the form of an equalization path, and the modules are divided into four types according to the arrangement condition of each single battery SOC in the module:

a. and (3) an energy-rich module: SOC (State of Charge) _a,j Greater than SOC _a And each single battery SOC in the module _i,j Are all larger than SOC _a ；

b. And (3) a starvation module: SOC (State of Charge) _a,j Less than SOC _a And each single battery SOC in the module _i,j Are all smaller than SOC _a ；

c. Quasi-energy-rich module: SOC (State of Charge) _a,j Greater than SOC _a But not all the single battery SOC in the module _i,j Are all larger than SOC _a There are certain cell SOCs _i,j Less than SOC _a ；

d. Quasi-starvation module: SOC (State of Charge) _a,j Less than SOC _a But not all the single battery SOC in the module _i,j Are all smaller than SOC _a There are certain cell SOCs _i,j Greater than SOC _a ；

The method specifically comprises the following steps of:

s731, judging whether hj and lj are equal to N at the same time, if so, indicating that the energy-rich and energy-deficient modules exist at the same time, executing S741, otherwise executing S732;

s732, judging h _j If the energy-rich modules are equal to N at the same time, if so, the energy-rich modules are only existed, S742 is executed, otherwise S733 is executed;

s733, judge l _j If equal to N, if yes, the instruction only has the deficient energy module, and S743 is executed; otherwise, it indicates that there are no rich and lean modules, and S744 is executed;

s74, dividing the equalization path into 4 forms:

a. the energy-rich module and the energy-deficient module are balanced;

b. the energy-rich module and the monomer battery with the minimum SOC in the quasi-energy-lack module are balanced;

c. the deficient energy module and the monomer battery with the largest SOC in the quasi-rich energy module are balanced;

d. the single battery with the largest SOC in the quasi-energy-rich module and the single battery with the smallest SOC in the quasi-energy-deficient module are balanced;

the method specifically comprises the following steps of:

s741 pair SOC _tj The minimum energy-rich module and the minimum energy-poor module are balanced;

s742, pair SOC _tj The weakest single battery in the minimum energy-rich module and the energy-short module is balanced;

S743, pair SOC _tj The strongest single battery in the minimum energy shortage module and the quasi-energy enrichment module is balanced;

s742, pair SOC _tj The strongest single battery in the smallest quasi-energy-rich module and the weakest single battery in the quasi-energy-poor module are balanced;

and S75, after the balance target module or the target single battery is selected, continuously performing balance operation on the balance target module or the target single battery until the balance condition is met by the target module or the target single battery, stopping current balance and reselecting the balance target.

Further, the equalization condition in the step S75 includes the following cases:

a. when the energy-rich module and the energy-deficient module are balanced, the SOC of the single battery with the minimum SOC inside the energy-rich module is reached _iL,jL Below SOC _a Or shortage ofSingle battery SOC with maximum SOC inside energy module _iH,jH Higher than SOC _a Stopping the current equalization;

b. when the single battery with the minimum SOC in the energy-rich module and the quasi-energy-short module is balanced, the single battery with the minimum SOC in the energy-rich module is balanced until the single battery with the minimum SOC in the energy-rich module is subjected to SOC _iL,jL Below SOC _a Or the SOC of the target single battery in the quasi-shortage energy module _il,jl Higher than SOC _a Stopping the current equalization;

c. when the single battery with the largest SOC in the energy shortage module and the quasi-energy-rich module is balanced, the single battery with the largest SOC in the energy shortage module reaches the SOC _iH,jH Higher than SOC _a Or quasi-energy-rich module internal target single battery SOC _ih,jh Below SOC _a Stopping the current equalization;

d. when the single battery with the largest SOC in the energy-rich module and the single battery with the smallest SOC in the energy-short module are aligned for balancing, the target single battery SOC in the energy-short module is reached _ih,jh Below SOC _a Or the SOC of the target single battery in the quasi-shortage energy module _il,jl Higher than SOC _a The current equalization is stopped.

Further, the step S75 includes the following sub-steps:

s751, judging SOC _iL,jL ≤SOC _a Or SOC (System on chip) _iH,jH ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

s752, judging SOC _iL,jL ≤SOC _a Or SOC (System on chip) _il,jl ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

s753, judging SOC _ih,jh ≤SOC _a Or SOC (System on chip) _iH,jH ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

s754, judging SOC _ih,jh ≤SOC _a Or SOC (System on chip) _il,jl ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, the current cycle is repeated.

Further, the step S8 includes the following sub-steps:

S81, judging whether the quasi-energy-rich module or the quasi-energy-lack module is ready for in-module equalization, if delta SOC _aj ≥SOC _a If so, the module is a quasi-energy-rich module, and S82 is executed; otherwise, as the quasi-starvation module, executing S83;

s82, judging the average SOC of the battery pack _a And the weakest single battery SOC in quasi-energy-rich module _il,jl Whether the difference is greater than a preset value ΔSOC _thc If true, execute S84; otherwise, not balancing;

s83, judging the average SOC of the battery pack _a SOC with strongest single battery in quasi-starvation energy module _ih,jh Whether the difference is greater than a preset value ΔSOC _thc If so, S84 is executed, otherwise, equalization is not performed;

s84, performing in-module equalization on the module, namely equalizing the strongest single battery and the weakest single battery in the module;

s85, after the balance target single battery is selected, continuously performing balance operation until the electric quantity of the original strongest single battery in the target single battery is smaller than the SOC _a Or the original weakest single battery electric quantity of the target single battery is larger than the SOC _a Stopping the current equalization and reselecting the equalization target, and returning to the step S1.

The beneficial effects of the invention are as follows: according to the decoupling modular active equalization method provided by the invention, the equalization lines among the modules are connected with the equalization buses of the modules, so that the coupling effect between the modules is relieved, the phenomenon of equalization overlapping of single batteries is avoided, and the equalization rate and the equalization efficiency are improved. In addition, the invention provides an equalization strategy which is suitable for an equalization circuit, and simulation results show that the equalization method can effectively avoid the phenomenon of equalization overlapping while guaranteeing the equalization rate and the equalization efficiency, avoid the phenomenon of repeated charge and discharge of the single battery caused by equalization overlapping, and reduce the influence of active equalization on the cycle life of the battery.

Drawings

FIG. 1 is a schematic diagram of a direct modular active equalization scheme;

FIG. 2 is a diagram of power transfer for direct modular active equalization;

fig. 3 is a circuit diagram of a decoupling modular active equalization circuit applied to a lithium battery pack according to the present invention;

FIG. 4 is a diagram of a decoupling modular active equalization power transfer in accordance with the present invention;

FIG. 5 is a flow chart of a decoupling modular active equalization strategy of the present invention;

FIG. 6 is a graph of the decoupling modular active equalization simulation results of the present invention;

FIG. 7 is a diagram of direct modular active equalization simulation results;

Detailed Description

The technical scheme of the invention is further described below with reference to the accompanying drawings.

The invention relates to a decoupling type modularized active equalization circuit applied to a lithium battery pack, which comprises M groups of module units with the same structure, and an inter-module equalization circuit (E _M ) The method comprises the steps of carrying out a first treatment on the surface of the As shown in fig. 3, where N is the number of cells in each module, M is the number of modules, subscript i (i=1, 2,3 … N) is the cell index, and subscript j (j=1, 2,3 … M) is the module index.

Each module unit includes a battery pack (B _i ) And in-module equalization circuitry (E) _c,i ) The method comprises the steps of carrying out a first treatment on the surface of the The battery pack is formed by connecting N single batteries in series, and each single battery is a lithium ion single battery of the same type;

the in-module equalizing circuit comprises a group of in-module switching tube arrays, a group of control switching tubes and a group of in-module equalizing inductors;

The in-module switching tube array comprises 2N+2 in-module switching tubes: one end of the switch tube in the 2i-1 th module and one end of the switch tube in the 2 i-th module are respectively connected with the positive electrode of the i-th single battery, wherein i=1, 2, … and N; one end of the 2N+1-th in-module switching tube is connected with the negative electrode of the N-th single battery;

the other end of the switching tube in the 2i-1 th module is connected to form a first equalizing bus, and the other end of the switching tube in the 2 i-th module is connected to form a second equalizing bus, i=1, 2, … and n+1;

one end of the control switch tube is connected with the first equalizing bus, the other end of the control switch tube is connected with one end of the equalizing inductance in the module, and the other end of the equalizing inductance in the module is connected with the second equalizing bus;

the inter-module equalization circuit includes a set of inter-module switching tube arrays (E _M ) And inter-module balancing inductance (L _M )；

The inter-module switching tube array includes 2M inter-module switching tubes (the inter-module switching tube amplifying circuit is shown in the upper right corner of fig. 3): one end of the switching tube between the 2j-1 th modules is connected with the first equalizing bus of the j-th module, and the other end of the switching tube between the 2j-1 th modules is connected to form the first equalizing bus between the modules; one end of the switching tube between the second modules is connected with a second equalizing bus of the second module, and the other end of the switching tube between the second modules is connected with the second equalizing bus of the second module; j=1, 2, …, M;

And two ends of the inter-module balance inductor are respectively connected with the first inter-module balance bus and the second inter-module balance bus.

Namely: in each group of modules, the single batteries are connected in series according to the order of the first single battery, the second single battery and the third single battery … Nth single battery to form a group of battery packs, and the battery packs of the M groups of module units are connected in series (each group of battery modules is connected in series according to the order of the first battery pack, the second battery pack and the third battery pack … Mth battery pack). In each group of modules, the first switching tube and the second switching tube are connected with the positive electrode of the first single battery, the third switching tube and the fourth switching tube are connected with the positive electrode of the second single battery, the … (th) N-1 switching tube and the 2 (th) N switching tube are connected with the positive electrode of the N single battery, and the 2N+1 (th) switching tube and the 2N+2 (th) switching tube are connected with the negative electrode of the N single battery; after one end of each switching tube is connected with a single battery, the other ends of the first switching tube, the third switching tube and the fifth switching tube …, namely the 2i-1 switching tube …, the 2N-1 switching tube and the 2N+1 switching tube are connected to form a first balanced bus, and the other ends of the second switching tube, the fourth switching tube and the sixth switching tube …, namely the 2i switching tube …, the 2N switching tube and the 2N+2 switching tube are connected to form a second balanced bus; one end of the control switch tube is connected with the first equalizing bus, the other end of the control switch tube is connected with one end of the equalizing inductance in the module, and the other end of the equalizing inductance in the module is connected with the second equalizing bus. The switching tube between the 1 st modules is connected with a first equalizing bus of the equalizing circuit in the 1 st module, and the switching tube between the 2 nd modules is connected with a second equalizing bus of the equalizing circuit between the 1 st modules; the 3 rd inter-module switching tube is connected with a first equalizing bus of the equalizing circuit in the 2 nd module, the 4 th inter-module switching tube is connected with a second equalizing bus of the equalizing circuit in the 2 nd module, the … nd inter-module switching tube is connected with a first equalizing bus of the equalizing circuit in the j-th module, the 2 j-th inter-module switching tube is connected with a second equalizing bus of the equalizing circuit in the j-th module, the … nd inter-module switching tube is connected with a first equalizing bus of the equalizing circuit in the M-th module, and the 2 nd inter-module switching tube is connected with a second equalizing bus of the equalizing circuit in the M-th module. After one end of each inter-module switching tube is connected with a corresponding first equalizing bus or a corresponding second equalizing bus, the other ends of the 2M-1 inter-module switching tubes of the first inter-module switching tube, the third inter-module switching tube and the fifth inter-module switching tube … and the 2j-1 inter-module switching tube … are connected to form a first inter-module equalizing bus, and the other ends of the 2M inter-module switching tubes of the second inter-module switching tube, the fourth inter-module switching tube and the sixth inter-module switching tube … and the 2j inter-module switching tube … are connected to form a second inter-module equalizing bus. And two ends of the inter-module balance inductance are respectively arranged on the first inter-module balance bus and the second inter-module balance bus.

Further, the switch tube in the module is composed of two bidirectional switch tubes formed by connecting two NMOS tube sources with the same type in series. The control switch tube is composed of two bidirectional switch tubes formed by connecting source electrodes of NMOS tubes with the same type in series. The inter-module switching tube is composed of two bi-directional switching tubes formed by connecting source electrodes of NMOS tubes of the same type in series.

In order to facilitate explanation of the decoupling type modular active equalization to avoid the phenomenon of equalization overlap, the electric quantity transfer diagram is used for explanation, as shown in fig. 4, the decoupling type modular active equalization is performed on two modules in state 1, and the equalization can be divided into three stages:

stage one: from state 1 to state 2, this stage performs inter-module equalization for both modules. The state 1 is that the single batteries in the two modules are in an unbalanced initial state, wherein the SOC of the three single batteries in the module 1 is larger than the SOC _a Therefore, the three single batteries can be balanced as a whole until the single battery with the lowest SOC, namely C _3,1 SOC with electric quantity less than or equal to _a Equalization is stopped. For module 2, of the three cells in the module, C _1,2 Is higher than SOC _a And C _2,2 And C _3,2 Is lower than SOC _a If the three single batteries are balanced as a whole, single battery C _1,2 Equalization overlap occurs, so that the single battery C with the lowest SOC in the module is singly subjected to _2,2 And carrying out inter-module equalization.

Three single batteries in module 1 are transferred 3S altogether ₁ Charge of the magnitude to the single cell C in the module 2 _3,2 。

Stage two: from state 2 to state 3, the second phase continues to perform inter-module equalization for both modules. Different from the first stage, the second stage is initiated, the unit cells C in the module 1 _3,1 The SOC has reached the SOC _a To avoid the equalization overlap, the module 1 cannot be equalized as a whole. Selecting the single battery C with highest SOC in the module 1 _1,1 Cell C lowest than SOC in module 2 _2,2 Performing inter-module equalization to obtain C _1,1 The electric quantity of (C) _2,2 Up to C _1,1 SOC of (2) reaches SOC _a Stopping equalization, at this time, cell C _2,2 The SOC of (2) was 50%. At this time, the electric quantity of the module 1 is still higher than that of the module 2, and the inter-module equalization needs to be continued, and a single battery C with the SOC being only higher than SOCa in the module 1 is selected _2,1 Cell C lowest than SOC in module 2 _2,2 (when two single batteries with the lowest SOC exist in one module, the single batteries with the lowest sequence in the module are selected) to perform inter-module equalization, and C is calculated _2,1 The electric quantity of (C) _2,2 Up to C _2,1 SOC of (2) reaches SOC _a Stopping equalization at this time C _2,2 SOC of (c) was 60%.

Single cell C inside module 1 _1,1 、C _2,1 Transfer S ₁ +S ₂ Charge of the magnitude to the single cell C in the module 2 _2,2 。

Stage three: state 3 to state 4, the third stage performs intra-module equalization on module 2. In state 3, the SOCs of the single batteries in the module 1 all reach SOCs _a The equilibrium state has been reached without the need for intra-module equalization. Single battery C with highest SOC in module 2 _1,2 Transferring electric quantity to single battery C with lowest SOC _3,2 Until each single battery SOC in the module 2 reaches SOC _a Equalization is stopped. At this time, all the single batteries in the two modules reach an equilibrium state, and the equilibrium operation is stopped.

The magnitude of the amount of charge transferred inside the module 2 is equal to the area S ₁ Size of the product.

The analysis shows that the charge quantity Q is transferred in the first, second and third stages _ed ＝5S ₁ +S ₂ =0.7q. Wherein the first stage and the second stage implement inter-module equalization so that the two modules SOC _a1 ＝SOC _a2 ＝SOC _a =60%, achieving inter-module equalization. And in the third stage, in-module equalization is implemented on the module 2, and finally, the equalization is completed. By decoupling, the SOC is higher than the SOC _a The electric quantity of the single battery of (2) is monotonically reduced and reaches the SOC _a And then stopping balancing the same; so that the SOC is lower than the SOC _a The electric quantity of the single battery of (1) rises monotonously and reaches the SOC _a And then the equalization is stopped, and the phenomenon of equalization overlapping is avoided.

The power transfer is described in stages, but in an actual equalization circuit, more modules are included, and the modules are balanced while the other modules are balanced in the modules. When a certain single battery in the module is balanced among the modules, the single battery SOC is towards the SOC _a Close to, not only has realized the balanced between the module, has also realized the inside balanced of module.

In order to avoid the equalization overlapping phenomenon, the invention provides an equalization strategy corresponding to an equalization circuit as shown in fig. 5, wherein the equalization flow comprises the following steps:

s1, the MCU collects the voltage of each single battery in the current series battery pack and carries out SOC estimation;

s2, calculating the SOC range delta SOC of each single battery;

s3, judging whether the extremely poor delta SOC is greater than or equal to the equilibrium preset value delta SOC _th If yes, the single battery is in an unbalanced state, and the balancing operation is needed to be carried out, and S4 is executed; otherwise, the single battery is in an equilibrium state, and the equilibrium operation is not needed, and the step S4 is executed;

s4, ending the operation;

s5, calculating the average value of the SOC of all the single batteries, and recording the average value as the SOC _a ；

S6, calculating the following data of each module:

a. average SOC: i.e. the average SOC of all the single batteries in each module, the average SOC of the jth module is recorded as SOC _a,j ；

b、SOC _a,j Is denoted as delta SOC _m ；

c. Extremely poor delta SOC of each single battery SOC in jth module _j ；

d. Calculating the in-module SOC of the j-th module _i,j Greater than SOC _a Number h of unit cells of (2) _j And less than SOC _a Number of unit cells l _j ；

e. For SOC _aj Greater than SOC _a The module of (2) calculates that the electric quantity is smaller than the SOC _a SOC of a single battery of (a) _i,j And SOC (System on chip) _a Sum of absolute value of difference SOC _tj The method comprises the steps of carrying out a first treatment on the surface of the For SOC _aj Less than SOC _a The module of (1) calculates that the electric quantity is larger than the SOC _a SOC of a single battery of (a) _i,j And SOC (System on chip) _a Sum of absolute value of difference SOC _tj ；

S7, an active equalization system controller performs inter-module equalization operation after processing the SOC of each single battery; comprises the following substeps:

s71, judging whether the maximum value of the average SOC difference values of all the modules exceeds the preset value delta SOC of the inter-module equalization _thm If (3)If yes, it is indicated that the imbalance between the modules is too large, and the balancing operation between the modules is required to be performed, and S731 is executed; otherwise, the battery modules are in an equilibrium state, and S72 is executed;

s72, not executing the inter-module equalization and ending the operation;

s73, the arrangement condition of each single battery SOC in the module influences the form of an equalization path, and the modules are divided into four types according to the arrangement condition of each single battery SOC in the module:

a. And (3) an energy-rich module: SOC (State of Charge) _a,j Greater than SOC _a And each single battery SOC in the module _i,j Are all larger than SOC _a ；

b. And (3) a starvation module: SOC (State of Charge) _a,j Less than SOC _a And each single battery SOC in the module _i,j Are all smaller than SOC _a ；

c. Quasi-energy-rich module: SOC (State of Charge) _a,j Greater than SOC _a But not all the single battery SOC in the module _i,j Are all larger than SOC _a There are certain cell SOCs _i,j Less than SOC _a ；

d. Quasi-starvation module: SOC (State of Charge) _a,j Less than SOC _a But not all the single battery SOC in the module _i,j Are all smaller than SOC _a There are certain cell SOCs _i,j Greater than SOC _a ；

The method specifically comprises the following steps of:

s731, judging whether hj and lj are equal to N at the same time, if so, indicating that the energy-rich and energy-deficient modules exist at the same time, executing S741, otherwise executing S732;

s732, judging h _j If the energy-rich modules are equal to N at the same time, if so, the energy-rich modules are only existed, S742 is executed, otherwise S733 is executed;

s733, judge l _j If equal to N, if yes, the instruction only has the deficient energy module, and S743 is executed; otherwise, it indicates that there are no rich and lean modules, and S744 is executed;

and S74, in order to avoid the occurrence of the balanced overlapping phenomenon, and fully improving the balanced power and the balanced efficiency among the modules according to the arrangement conditions of different single battery SOCs in the modules. When there is a rich energy mode When the module is blocked or starved, because the SOC of each single battery in the module is larger or smaller than the SOC _a The module is taken as a whole to be balanced, so that the SOC of all the single batteries in the module can be simultaneously approximate to the SOC _a The method comprises the steps of carrying out a first treatment on the surface of the When the energy-rich module or the energy-short module is aligned for equalization, because the SOC of each single battery inside the module is distributed at the SOC _a If the upper and lower sides of the module are balanced as a whole, an equalization overlapping phenomenon occurs, equalization power is lost, and equalization efficiency is reduced. The equalization path can be divided into 4 forms for this purpose:

a. the energy-rich module and the energy-deficient module are balanced;

b. the energy-rich module and the monomer battery with the minimum SOC in the quasi-energy-lack module are balanced;

c. the deficient energy module and the monomer battery with the largest SOC in the quasi-rich energy module are balanced;

d. the single battery with the largest SOC in the quasi-energy-rich module and the single battery with the smallest SOC in the quasi-energy-deficient module are balanced;

when a plurality of modules with identical SOC arrangement of the internal single batteries exist at the same time, the SOC is preferentially selected _tj A small module. For one module, SOC _tj The smaller the time required for in-module equalization is, the shorter the time required for in-module equalization is; whereas the longer the time required for equalization within the module. And for the same module, the in-module equalization and the inter-module equalization cannot be performed simultaneously, and the SOC _tj The small modules have short inter-module balancing time, the inter-module balancing is firstly carried out on the small modules, and after the modules reach the balancing, the intra-module balancing is carried out; rear pair SOC _tj Large modules perform inter-module equalization. By the inter-module balancing mode, the time required by balancing is sufficiently reduced.

The method specifically comprises the following steps of:

s741 pair SOC _tj The minimum energy-rich module and the minimum energy-poor module are balanced;

s742, pair SOC _tj The weakest single battery in the minimum energy-rich module and the energy-short module is balanced;

s743, pair SOC _tj Minimum energy shortage module and quasi-energy enrichment moduleEqualizing the strongest single battery;

s742, pair SOC _tj The strongest single battery in the smallest quasi-energy-rich module and the weakest single battery in the quasi-energy-poor module are balanced;

and S75, in order to avoid frequent switching of the equalization target battery during equalization to cause frequent switching of the equalization path, after the equalization target module or the target single battery is selected, continuously performing equalization operation on the equalization target module or the target single battery until the target module or the target single battery meets the equalization condition, stopping current equalization and reselecting the equalization target.

The equalization conditions include the following:

a. when the energy-rich module and the energy-deficient module are balanced, the SOC of the single battery with the minimum SOC inside the energy-rich module is reached _iL,jL Below SOC _a Or the single battery SOC with the largest internal SOC of the deficient energy module _iH,jH Higher than SOC _a Stopping the current equalization;

b. when the single battery with the minimum SOC in the energy-rich module and the quasi-energy-short module is balanced, the single battery with the minimum SOC in the energy-rich module is balanced until the single battery with the minimum SOC in the energy-rich module is subjected to SOC _iL,jL Below SOC _a Or SOC of target single battery (single battery with minimum primary SOC) in quasi-starvation energy module _il,jl Higher than SOC _a Stopping the current equalization;

c. when the single battery with the largest SOC in the energy shortage module and the quasi-energy-rich module is balanced, the single battery with the largest SOC in the energy shortage module reaches the SOC _iH,jH Higher than SOC _a Or the SOC of a target single battery (the single battery with the maximum primary SOC) in the quasi-energy-rich module _ih,jh Below SOC _a Stopping the current equalization;

d. when the single battery with the largest SOC in the energy-rich module and the single battery with the smallest SOC in the energy-short module are aligned and balanced, the SOC of the target single battery (the single battery with the largest primary SOC) in the energy-short module is reached _ih,jh Below SOC _a Or SOC of target single battery (single battery with minimum primary SOC) in quasi-starvation energy module _il,jl Higher than SOC _a The current equalization is stopped.

S75 specifically comprises the following sub-steps:

s751, judging SOC _iL,jL ≤SOC _a Or SOC (System on chip) _iH,jH ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

S752, judging SOC _iL,jL ≤SOC _a Or SOC (System on chip) _il,jl ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

s753, judging SOC _ih,jh ≤SOC _a Or SOC (System on chip) _iH,jH ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

s754, judging SOC _ih,jh ≤SOC _a Or SOC (System on chip) _il,jl ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, the current cycle is repeated.

S8, an active equalization system controller performs in-module equalization operation after processing the SOC of each single battery; and the inter-module equalization and the intra-module equalization are performed simultaneously, and the intra-module equalization only selects a quasi-energy-rich module and a quasi-energy-lack module which do not perform inter-module equalization, so that the phenomenon of equalization overlapping is avoided.

The method comprises the following sub-steps:

s81, judging whether the quasi-energy-rich module or the quasi-energy-lack module is ready for in-module equalization, if delta SOC _aj ≥SOC _a If so, the module is a quasi-energy-rich module, and S82 is executed; otherwise, as the quasi-starvation module, executing S83;

s82, judging the average SOC of the battery pack _a And the weakest single battery SOC in quasi-energy-rich module _il,jl Whether the difference is greater than a preset value ΔSOC _thc If true, execute S84; otherwise, not balancing;

in the quasi-rich module, the single battery with the lowest SOC is SOC _il,jl And SOC (System on chip) _a Near, i.e. satisfy SOC _a -SOC _il,jl ≤ΔSOC _thc The single batteries reach an equilibrium state, and the electric quantity is higher than the SOC _a The single battery can reach an equilibrium state through the equilibrium among the modules.

S83, judging the average SOC of the battery pack _a SOC with strongest single battery in quasi-starvation energy module _ih,jh Whether the difference is greater than a preset value ΔSOC _thc If so, S84 is executed, otherwise, equalization is not performed;

in the quasi-starvation energy module, the single battery with highest SOC is SOC _ih,jh And SOC (System on chip) _a Near, i.e. satisfy SOC _ih,jh -SOC _a ≥ΔSOC _thc The single batteries reach an equilibrium state, and the electric quantity is lower than the SOC _a The single battery can reach an equilibrium state through the equilibrium among the modules.

S84, performing in-module equalization on the module, namely equalizing the strongest single battery and the weakest single battery in the module;

s85, in order to avoid frequent switching of the equalization target single battery during equalization to cause frequent switching of the equalization path, after the equalization target single battery is selected, equalization operation is continuously performed on the equalization target single battery until the original strongest single battery electric quantity of the target single battery is smaller than the SOC _a Or the original weakest single battery electric quantity of the target single battery is larger than the SOC _a Stopping the current equalization and reselecting the equalization target, and returning to the step S1.

Through the decoupling type modularized active equalization circuit and the corresponding equalization strategy, a group of battery packs comprising 25 single batteries are divided into 5 modules, and each module comprises 5 single batteries, wherein the initial SOC of each 25 single batteries is 78.9%, 45.7%, 45.9%, 20.4%, 23.1%, 85.6%, 25.6%, 85.6%, 65.0%, 49.5%, 42.0%, 43.5%, 46.9%, 42.0%, 42.1%, 56.3%, 56.9%, 26.6%, 42.3%, 75.1%, 52.0%, 75.6%, 20.6%, 51.3% and 75.2% respectively. As a result of the equalization, as shown in fig. 6, the total consumption took 118 minutes to reach an equalized state, and the average SOC of each cell after the equalization was 50.2%. Each single battery monotonously faces to average SOC _a Close together without balancing weightStacking phenomenon.

For comparison, direct modular equalization simulation was performed on the battery packs with the same initial SOC, and the equalization results are shown in fig. 7. The total consumption took 130 minutes to reach an equilibrium state, and the average SOC of each cell after the completion of the equilibrium was 49.9%. It is obvious that the balanced overlapping phenomenon of the single batteries is observed, and the single battery C in the figure _er For example, its SOC undergoes three phases of descent, ascent, descent.

Those of ordinary skill in the art will recognize that the embodiments described herein are for the purpose of aiding the reader in understanding the principles of the present invention and should be understood that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit thereof, and such modifications and combinations remain within the scope of the present disclosure.

Claims (7)

1. The decoupling type modularized active equalization circuit applied to the lithium battery pack is characterized by comprising M groups of module units with the same structure and an inter-module equalization circuit;

each module unit comprises a battery pack and an in-module equalization circuit; the battery pack is formed by connecting N single batteries in series;

the in-module equalizing circuit comprises a group of in-module switching tube arrays, a group of control switching tubes and a group of in-module equalizing inductors;

the in-module switching tube array comprises 2N+2 in-module switching tubes: one end of the switch tube in the 2i-1 th module and one end of the switch tube in the 2 i-th module are respectively connected with the positive electrode of the i-th single battery, wherein i=1, 2, … and N; one end of the 2N+1-th in-module switching tube is connected with the negative electrode of the N-th single battery;

The other end of the switching tube in the 2i-1 th module is connected to form a first equalizing bus, and the other end of the switching tube in the 2 i-th module is connected to form a second equalizing bus, i=1, 2, … and n+1;

one end of the control switch tube is connected with the first equalizing bus, the other end of the control switch tube is connected with one end of the equalizing inductance in the module, and the other end of the equalizing inductance in the module is connected with the second equalizing bus;

the inter-module balancing circuit comprises a group of inter-module switching tube arrays and inter-module balancing inductors;

the inter-module switching tube array comprises 2M inter-module switching tubes: one end of the switching tube between the 2j-1 th modules is connected with a first equalizing bus of each j-th module, and the other end of the switching tube between the 2j-1 th modules is connected to form a first equalizing bus between the modules; one end of the switching tube between the second modules is connected with a second equalizing bus of the second module, and the other end of the switching tube between the second modules is connected with the second equalizing bus of the second module; j=1, 2, …, M;

two ends of the inter-module balance inductor are respectively connected with a first inter-module balance bus and a second inter-module balance bus;

the switch tube in the module is composed of two bidirectional switch tubes formed by connecting two NMOS tube sources with the same type in series;

The control switch tube is composed of two bidirectional switch tubes formed by connecting source electrodes of NMOS tubes with the same type in series;

the inter-module switching tube is composed of two bi-directional switching tubes formed by connecting source electrodes of NMOS tubes with the same type in series;

while balancing among modules, balancing other modules in the modules; when a certain single battery in the module is balanced among the modules, the single battery SOC approaches to the average value SOCa of all the single battery SOCs.

2. The decoupling modular active equalization circuit for use in a lithium battery pack of claim 1, wherein M groups of said modular cells are connected in series.

3. The equalization strategy of a decoupled modular active equalization circuit applied to a lithium battery pack according to claim 1 or 2, comprising the steps of:

s1, the MCU collects the voltage of each single battery in the current series battery pack and carries out SOC estimation;

s2, calculating the SOC range delta SOC of each single battery;

s3, judging whether the extremely poor delta SOC is greater than or equal to the equilibrium preset value delta SOC _th If yes, the single battery is in an unbalanced state, and the balancing operation is needed, and S5 is executed; otherwise, the single battery is in an equilibrium state, and the equilibrium operation is not needed, and the step S4 is executed;

S4, ending the operation;

s5, calculating the average value of the SOC of all the single batteries, and recording the average value as the SOC _a ；

S6, calculating the following data of each module:

a. average SOC: i.e. the average SOC of all the single batteries in each module, the average SOC of the jth module is recorded as SOC _a,j ；

b、SOC _a,j Is denoted as delta SOC _m ；

c. Extremely poor delta SOC of each single battery SOC in jth module _j ；

d. Calculating the SOC of the single battery in the j-th module _i,j Greater than SOC _a Number h of unit cells of (2) _j And less than SOC _a Number of unit cells l _j ；

e. For SOC _a，j Greater than SOC _a The module of (2) calculates that the electric quantity is smaller than the SOC _a SOC of a single battery of (a) _i,j And SOC (System on chip) _a Sum of absolute value of difference SOC _tj The method comprises the steps of carrying out a first treatment on the surface of the For SOC _a，j Less than SOC _a The module of (1) calculates that the electric quantity is larger than the SOC _a SOC of a single battery of (a) _i,j And SOC (System on chip) _a Sum of absolute value of difference SOC _tj ；

S7, an active equalization system controller performs inter-module equalization operation after processing the SOC of each single battery;

s8, the active equalization system controller executes the in-module equalization operation after processing the SOC of each single battery.

4. The equalization strategy applied to a decoupled modular active equalization circuit of a lithium battery pack of claim 3, wherein said step S7 comprises the sub-steps of:

s71, judging whether the maximum value of the average SOC difference values of all the modules exceeds the preset value delta SOC of the inter-module equalization _thm If yes, the unbalance among the modules is too large, and the balancing operation among the modules is needed to be carried out, and S73 is executed; otherwise, the battery modules are in an equilibrium state, and S72 is executed;

s72, not executing the inter-module equalization and ending the operation;

s73, the arrangement condition of each single battery SOC in the module influences the form of an equalization path, and the modules are divided into four types according to the arrangement condition of each single battery SOC in the module:

a. and (3) an energy-rich module: SOC (State of Charge) _a,j Greater than SOC _a And each single battery SOC in the module _i,j Are all larger than SOC _a ；

b. And (3) a starvation module: SOC (State of Charge) _a,j Less than SOC _a And each single battery SOC in the module _i,j Are all smaller than SOC _a ；

c. Quasi-energy-rich module: SOC (State of Charge) _a,j Greater than SOC _a But not all the single battery SOC in the module _i,j Are all larger than SOC _a There are certain cell SOCs _i,j Less than SOC _a ；

d. Quasi-starvation module: SOC (State of Charge) _a,j Less than SOC _a But not all the single battery SOC in the module _i,j Are all smaller than SOC _a There are certain cell SOCs _i,j Greater than SOC _a ；

The method specifically comprises the following steps of:

s731, judging whether hj and lj are equal to N at the same time, if so, indicating that the energy-rich and energy-deficient modules exist at the same time, executing S741, otherwise executing S732;

s732, judging h _j If equal to N, if yes, it is indicated that only the energy-rich module exists, S742 is executed, otherwise S733 is executed;

S733, judge l _j If equal to N, if yes, the instruction only has the deficient energy module, and S743 is executed; otherwise, it indicates that there are no rich and lean modules, and S744 is executed;

s74, dividing the equalization path into 4 forms:

a. the energy-rich module and the energy-deficient module are balanced;

b. the energy-rich module and the monomer battery with the minimum SOC in the quasi-energy-lack module are balanced;

c. the deficient energy module and the monomer battery with the largest SOC in the quasi-rich energy module are balanced;

d. the single battery with the largest SOC in the quasi-energy-rich module and the single battery with the smallest SOC in the quasi-energy-deficient module are balanced;

the method specifically comprises the following steps of:

s741 pair SOC _tj The minimum energy-rich module and the minimum energy-poor module are balanced;

s742, pair SOC _tj The weakest single battery in the minimum energy-rich module and the energy-short module is balanced;

s743, pair SOC _tj The strongest single battery in the minimum energy shortage module and the quasi-energy enrichment module is balanced;

s744 to SOC _tj The strongest single battery in the smallest quasi-energy-rich module and the weakest single battery in the quasi-energy-poor module are balanced;

and S75, after the balance target module or the target single battery is selected, continuously performing balance operation on the balance target module or the target single battery until the balance condition is met by the target module or the target single battery, stopping current balance and reselecting the balance target.

5. The equalization strategy of the decoupling and modular active equalization circuit applied to a lithium battery pack as claimed in claim 4, wherein the equalization conditions in said step S75 comprise the following cases:

a. when the energy-rich module and the energy-deficient module are balanced, the SOC of the single battery with the minimum SOC inside the energy-rich module is reached _iL,jL Below SOC _a Or the single battery SOC with the largest internal SOC of the deficient energy module _iH,jH Higher than SOC _a Stopping the current equalization;

b. when the single battery with minimum SOC in the energy-rich module and the energy-short module is balanced, the energy-rich module and the energy-short module are balanced untilSingle battery SOC with minimum internal SOC of energy-rich module _iL,jL Below SOC _a Or the SOC of the target single battery in the quasi-shortage energy module _il,jl Higher than SOC _a Stopping the current equalization;

c. when the single battery with the largest SOC in the energy shortage module and the quasi-energy-rich module is balanced, the single battery with the largest SOC in the energy shortage module reaches the SOC _iH,jH Higher than SOC _a Or quasi-energy-rich module internal target single battery SOC _ih,jh Below SOC _a Stopping the current equalization;

d. when the single battery with the largest SOC in the energy-rich module and the single battery with the smallest SOC in the energy-short module are aligned for balancing, the target single battery SOC in the energy-short module is reached _ih,jh Below SOC _a Or the SOC of the target single battery in the quasi-shortage energy module _il,jl Higher than SOC _a The current equalization is stopped.

6. The equalization strategy of a decoupled modular active equalization circuit applied to a lithium battery pack of claim 4, wherein said step S75 comprises the sub-steps of:

s751, judging SOC _iL,jL ≤SOC _a Or SOC (System on chip) _iH,jH ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

s752, judging SOC _iL,jL ≤SOC _a Or SOC (System on chip) _il,jl ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

s753, judging SOC _ih,jh ≤SOC _a Or SOC (System on chip) _iH,jH ≥SOC _a If so, stopping the current inter-module equalization, and reselecting the inter-module equalization target; otherwise, repeating the current cycle;

s754, judging SOC _ih,jh ≤SOC _a Or SOC (System on chip) _il,jl ≥SOC _a If so, stopping the current inter-module equalization and reselecting the moduleA inter-equalization target; otherwise, the current cycle is repeated.

7. The equalization strategy of the decoupling modular active equalization circuit applied to lithium battery packs of claim 4, wherein said intra-module equalization in step S8 comprises the sub-steps of:

s81, judging whether the module ready for in-module equalization is a quasi-energy-rich module or a quasi-energy-lack module, if delta SOC _aj ≥SOC _a If so, the module is a quasi-energy-rich module, and S82 is executed; otherwise, as the quasi-starvation module, executing S83;

s82, judging the average SOC of the battery pack _a And the weakest single battery SOC in quasi-energy-rich module _il,jl Whether the difference is greater than a preset value ΔSOC _thc If true, execute S84; otherwise, not balancing;

s83, judging the average SOC of the battery pack _a SOC with strongest single battery in quasi-starvation energy module _ih,jh Whether the difference is greater than a preset value ΔSOC _thc If so, S84 is executed, otherwise, equalization is not performed;

s84, performing in-module equalization on the module, namely equalizing the strongest single battery and the weakest single battery in the module;

s85, after the balance target single battery is selected, continuously performing balance operation until the electric quantity of the original strongest single battery in the target single battery is smaller than the SOC _a Or the original weakest single battery electric quantity of the target single battery is larger than the SOC _a Stopping the current equalization and reselecting the equalization target, and returning to the step S1.