Battery pack active equalization circuit based on multi-transformer equalization sub-module

Abstract

The application discloses a battery pack active equalization circuit based on a multi-transformer equalization sub-module, which comprises a front-stage circuit, k multi-winding transformers, a rear-stage circuit and n series-connected battery cells; the front-stage circuit transforms a direct-current voltage into a high-frequency pulsating voltage or a high-frequency alternating voltage; the primary winding of the k transformers is connected in series, in parallel or in series-parallel between a first primary connection point and a second primary connection point, and the secondary winding is connected with n output units of the rear-stage circuit in one-to-one correspondence; the output capacitor of each output unit is connected in parallel with a corresponding battery cell, and m groups of equalization capacitor networks are connected between corresponding nodes of each output unit; the n output units share a same power switch network, energy is transferred through the transformers and is transferred among the battery cells through the equalization capacitor networks, so that voltage self-equalization is realized; and the circuit can be expanded layer by layer as an equalization sub-module.

Description

Technical Field

[0001] This invention relates to the field of battery balancing technology, and specifically to an active balancing circuit for battery packs based on a multi-transformer balancing submodule. Background Technology

[0002] Lithium-ion batteries, as key energy storage devices in the new energy industry, are widely used in electric vehicles, grid energy storage, communication base stations, and power monitoring systems. Due to the limited voltage and capacity of individual battery cells, multiple cells are typically connected in series to form a battery pack to meet the system's requirements for output voltage and energy storage capacity. However, influenced by factors such as manufacturing processes, material properties, initial capacity, differences in internal resistance, and operating environment, inconsistencies may exist among the individual cells in the initial state of the battery pack. During long-term charge and discharge, these inconsistencies are further exacerbated by changes in the electrochemical characteristics of each cell. Inconsistencies between cells can cause some cells to reach their charging or discharging limits prematurely, leading to overcharging, over-discharging, decreased capacity utilization, and shortened cycle life. In severe cases, this can even cause safety hazards such as thermal runaway. Therefore, effective energy balancing of series-connected battery packs is a crucial technical means to improve the usable capacity of the battery pack, extend its service life, and ensure the safe operation of the system.

[0003] Existing battery balancing technologies can generally be divided into two categories based on their energy processing methods: passive balancing and active balancing. Passive balancing typically dissipates excess energy in battery cells with higher voltage or state of charge (SOC) as heat through energy-consuming resistors. While its circuit structure is simple and low-cost, it wastes balancing energy unnecessarily, resulting in low balancing efficiency. Furthermore, it introduces additional heat dissipation challenges in large-capacity battery pack applications. Active balancing, on the other hand, uses energy transfer units such as inductors, capacitors, transformers, or power electronic converters to transfer energy from battery cells with higher voltage or SOC to those with lower SOC. This effectively improves energy utilization and balancing efficiency, and has become the main development direction for series battery pack balancing technology.

[0004] In active balancing technology, converter-based balancing schemes have attracted widespread attention due to their controllable balancing current and fast balancing speed. For example, Chinese patent document CN108923508B discloses a battery active balancing device containing a flyback converter. This device forms a series flyback balancing circuit through a drive unit and multiple balancing units. Each balancing unit is connected to a single battery cell, enabling energy transfer between the battery pack and individual cells, thereby achieving active balancing of multiple battery cells. This type of scheme can improve balancing efficiency to a certain extent, but its balancing units need to be set up separately for each battery cell, and the number of controllable switches must be the same as the number of battery cells. When the number of series-connected battery cells increases, the number of balancing units, the number of controllable switches, connection branches, and control channels all increase accordingly, leading to an increase in circuit size, cost, and control complexity, and limiting the circuit's scalability.

[0005] Equalization schemes based on multi-winding transformers are another typical type of active equalization technology. Chinese patent document CN102684263B discloses an equalization circuit for a series battery pack based on a symmetrical multi-winding transformer structure and a control method applied to this circuit. This circuit sets up multi-winding transformers for each battery cell, and each battery cell includes a filter, a high-frequency switch, a current-limiting resistor, a magnetic reset, a soft-switching resonant circuit, and a drive circuit for driving the high-frequency switch on and off. Energy transfer between battery cells is achieved by controlling the on / off state of each high-frequency switch. In this scheme, each battery cell needs to be equipped with a high-frequency switch and its drive circuit and magnetic reset circuit. The number of switching devices and their supporting circuits increases with the number of battery cells. Furthermore, as the number of series-connected battery cells increases, the number of windings in the symmetrical multi-winding transformer increases accordingly, making the transformer winding process complex and making it difficult to guarantee the consistency of the parameters of each winding.

[0006] Chinese patent document CN107834655A discloses an automatic battery equalization circuit and its implementation method based on a multi-winding transformer. In this circuit, each battery pack corresponds to a multi-winding transformer. The secondary windings of all multi-winding transformers are connected in parallel and each is connected to its corresponding battery pack via a diode. The positive and negative terminals of each battery cell are connected to the corresponding transformer winding via a switching transistor. A microcontroller simultaneously controls the on and off states of each switching transistor using a single PWM control signal. Chinese patent document CN108964195A discloses a battery equalizer utilizing a multi-winding transformer. This equalizer winds multiple coils with the same number of turns on a magnetic core. Every two battery cells share one winding, and each battery cell uses a MOSFET switching device. Equalization is achieved by driving all MOSFETs through complementary switching signals. While the two schemes mentioned above simplify the generation of control signals, each battery cell still needs to be equipped with its own switching transistor, and the number of switching devices still increases with the number of battery cells. At the same time, in high-string-count applications with a large number of battery cells, multi-winding transformers need to wind a large number of windings on the same magnetic core. The winding process, turn consistency and leakage inductance control all face great difficulties, which limits the expansion of the equalization circuit to higher-string-count battery packs.

[0007] In summary, existing active balancing circuits generally suffer from the following problems: Firstly, the number of controllable switching devices and their driving and control branches is related to the number of series-connected battery cells. As the number of battery cells increases, the circuit complexity, control difficulty, and system cost rise significantly. Secondly, balancing schemes relying on a single multi-winding transformer have high requirements for transformer winding technology, making it difficult to guarantee winding consistency, and resulting in insufficient circuit scalability. Therefore, how to improve the scalability of active balancing circuits while ensuring low control complexity and low circuit cost is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] This invention provides an active balancing circuit for battery packs based on a multi-transformer balancing submodule. Compared with traditional battery balancing circuits, it reduces the number of switching devices, and the number of switching devices does not increase with the number of series-connected battery cells. Furthermore, it allows the replacement of a single multi-winding transformer with a large number of windings with multiple multi-winding transformers with fewer secondary windings, reducing the requirements for transformer winding technology and enabling lower-cost expansion of high-series-count battery pack applications.

[0009] The technical solution adopted in this invention is as follows: The battery pack active balancing circuit based on a multi-transformer balancing submodule includes: The circuit consists of a front-end circuit, k multi-winding transformers, a back-end circuit, and a battery pack composed of n battery cells connected in series, where: k is an integer and 2≤k≤n, and n is an integer and n≥2; The front-end circuit includes a DC input terminal, a power switch network, a first primary-side connection point, and a second primary-side connection point. The two ends of the DC input terminal are used to connect to the two poles of the DC input source. One end of the power switch network is connected to the DC input terminal, and the other end of the power switch network is connected to the first primary side connection point and the second primary side connection point. The front-end circuit is used to perform high-frequency switching modulation of the DC voltage at the DC input terminal through a power switching network, forming a high-frequency pulsating voltage or a high-frequency alternating voltage between the first primary-side connection point and the second primary-side connection point. Each multi-winding transformer includes one primary winding and at least one secondary winding; the primary windings of k multi-winding transformers form a series, parallel, or series-parallel circuit structure, one end of which is connected to a first primary connection point, and the other end of which is connected to a second primary connection point; the sum of the number of secondary windings of the k multi-winding transformers is n; The subsequent circuit includes n output units and m sets of equalizing capacitor networks, where m is a positive integer; each output unit includes a pair of secondary side connection points and an output capacitor; the output unit is used to rectify the high-frequency voltage output from the corresponding secondary winding into a DC voltage; One end of each secondary winding is connected to one of the two secondary connection points of the corresponding output unit, and the other end of each secondary winding is connected to the other connection point of the two secondary connection points of the corresponding output unit. One terminal of the output capacitor of each output unit is connected to one terminal of the corresponding battery cell, and the other terminal of the output capacitor is connected to the other terminal of the corresponding battery cell. The equalizing capacitor network is connected between corresponding nodes of each output unit to form charge transfer paths between different output units; Each of the n battery cells corresponds to one of the n output units, and the n output units share the power switching network of the front-end circuit. Energy is transferred to the back-end circuit through k multi-winding transformers and then transferred between different battery cells through the equalizing capacitor network to achieve voltage balance among the n series-connected battery cells.

[0010] The power switching network includes at least one power switching device, and the power switching network is configured to turn on and off the at least one power switching device under the control of a drive signal to perform high-frequency switching modulation on the DC voltage connected to the DC input terminal. The front-end circuit is a flyback, forward, full-bridge, half-bridge, or push-pull circuit structure. When the front-end circuit adopts a push-pull circuit structure, the front-end circuit also includes a primary-side center tap connection point. The power switching network forms a high-frequency pulsating voltage or a high-frequency alternating voltage between the first primary-side connection point and the primary-side center tap connection point, and between the second primary-side connection point and the primary-side center tap connection point.

[0011] When all k primary windings of the multi-winding transformer are provided with center taps, and two or more of the k primary windings are connected in series, each primary winding is divided into a first half-winding and a second half-winding with its center tap as the boundary; the first half-windings of each primary winding are connected in series in sequence and then connected between the first primary winding connection point and the primary center tap connection point; the second half-windings of each primary winding are connected in series in sequence and then connected between the second primary winding connection point and the primary center tap connection point.

[0012] The m-group equalization capacitor network includes three basic connection methods: Type I, Type II, and Type III, and their combinations; Type I connection method is as follows: connect a balancing capacitor between the corresponding nodes of any two adjacent output units. Each balancing capacitor network includes n-1 balancing capacitors, where m is 1 or 2. Type II connection method: Any node of an output unit is used as a common node. This common node is connected to the corresponding nodes of the remaining output units via a balancing capacitor. Each balancing capacitor network includes n-1 balancing capacitors, where m is an integer and 1 ≤ m ≤ 2(n...). 1); The Type III connection method is as follows: the corresponding node of each output unit is connected to one end of a balancing capacitor, and the other end of each balancing capacitor is connected to the same common point. Each balancing capacitor network includes n balancing capacitors, where m is 1 or 2.

[0013] The output unit is a bridge full-wave rectifier structure, and the r-th output unit includes a secondary winding ( L Sr ), by rectifier diode (D) r1 ), rectifier diode (D) r2 ), rectifier diode (D) r3 ) and rectifier diodes (D r4 The rectifier bridge (BR) consists of r and output capacitor () C r ), where r∈{1,2,…,n}; The rectifier diode (D) r1 The anode of the rectifier diode (D) is connected to the rectifier diode. r3 The anode of the rectifier diode (D) r1The cathode of the rectifier diode (D) is connected to the cathode. r2 The anode of the rectifier diode (D) r2 The cathode of the rectifier diode (D) is connected to the cathode of the rectifier diode. r4 The cathode of the rectifier diode (D) r3 The cathode of the rectifier diode (D) is connected to the cathode of the rectifier diode. r4 The anode of ) The secondary winding ( L Sr The same terminal of the rectifier diode (D) is connected to the same terminal of the rectifier diode. r1 The cathode and rectifier diode (D) r2 The anode of the secondary winding () L Sr The non-identical terminal of the rectifier diode (D) is connected to the other terminal. r3 The cathode and rectifier diode (D) r4 The anode of ) The output capacitor ( C r The positive terminal of the rectifier diode (D) is connected to the positive terminal of the rectifier diode. r2 The cathode and rectifier diode (D) r4 The cathode of the output capacitor () C r The negative terminal of the rectifier diode (D) is connected to the negative terminal of the rectifier diode. r1 The anode and rectifier diode (D) r3 The anode of ).

[0014] The output unit is an isolated Zeta structure, and the r-th output unit includes a secondary winding ( L Sr ), series capacitor ( C sr ), rectifier diode (D) r ), output filter inductor ( L r and output capacitor () C r ), where r∈{1,2,…,n}; The series capacitor ( C sr One end of the winding is connected to the secondary winding. L Sr The same terminal of the series capacitor () C sr The other end is connected to a rectifier diode (D). r The cathode and output filter inductor () L r one end of ); The output capacitor ( C r The positive terminal of the output filter inductor is connected to the positive terminal of the output filter inductor.L r At the other end of the output capacitor ( C r The negative terminal of the rectifier diode (D) is connected to the negative terminal of the rectifier diode. r The anode and secondary windings of ) L Sr () Non-same-name end.

[0015] The output unit is a center-tapped full-wave rectifier structure, and the r-th output unit includes a secondary winding with a center tap ( L Sr ), rectifier diode (D) r1 ), rectifier diode (D) r2 and output capacitor () C r ), where r∈{1,2,…,n}; The rectifier diode (D) r1 The anode of the secondary winding is connected to the anode of the secondary winding. L Sr The rectifier diode (D) is located at the same terminal as the rectifier diode. r1 The cathode of the rectifier diode (D) is connected to the cathode of the rectifier diode. r2 The cathode of the cathode and the output capacitor ( C r The positive electrode; The rectifier diode (D) r2 The anode of the secondary winding is connected to the anode of the secondary winding. L Sr The output capacitor () is a non-identical terminal. C r The negative terminal of the secondary winding (LSr) is connected to the center tap.

[0016] The output unit is a half-wave rectifier structure, the first... i The output unit includes the secondary winding ( L Si ), rectifier diode (D) i and output capacitor () C i ),in i ∈{1,2,…,n}; The secondary winding ( L Si The same terminal of the rectifier diode (D) is connected to the same terminal of the rectifier diode. i The anode of the rectifier diode (D) i The cathode of the output capacitor is connected to the cathode. C i The positive terminal of the secondary winding () L Si The non-identical terminals of the output capacitor are connected to the output capacitor.C i The negative electrode of ) No. i Each battery cell (B) i The positive terminal connection of the first i Output capacitor in the output unit ( C i The positive terminal of the rectifier diode (D) and the positive terminal of the rectifier diode (D) i The cathode of ) i Each battery cell (B) i The negative terminal connection of the first i Output capacitor in the output unit ( C i The negative and secondary windings of ) L Si The non-same-name ends of ) where i∈{1,2,…,n}.

[0017] The battery pack active balancing circuit constitutes a balancing submodule, and the battery pack in the balancing submodule is equivalent to a single battery to be balanced; the balancing submodule is connected to at least one other balancing submodule through the newly added k' multi-winding transformers and the newly added m' balancing capacitor network, and expands layer by layer to form a multi-layer balancing circuit, where k' and m' are both positive integers.

[0018] The battery pack active balancing circuit combination extension method based on multi-transformer balancing submodules includes the following steps: Step S1: Configure the front-end circuit: The front-end circuit includes a DC input terminal, a power switch network, a first primary-side connection point, and a second primary-side connection point. One end of the power switch network is connected to the DC input terminal, and the other end of the power switch network is connected to the first primary-side connection point and the second primary-side connection point, so that the front-end circuit performs high-frequency switching modulation on the DC voltage connected to the DC input terminal through the power switch network, forming a high-frequency pulsating voltage or a high-frequency alternating voltage between the first primary-side connection point and the second primary-side connection point. Step S2: Configure k multi-winding transformers: Each multi-winding transformer includes one primary winding and at least one secondary winding. The primary windings of the k multi-winding transformers are arranged in series, parallel, or series-parallel circuit structures. One end of the series, parallel, or series-parallel circuit structure is connected to the first primary winding connection point, and the other end of the series, parallel, or series-parallel circuit structure is connected to the second primary winding connection point. The sum of the number of secondary windings of the k multi-winding transformers is n, where k is an integer and 1≤k≤n, and n is an integer and n≥2. Step S3: Configure the subsequent circuit and combine it to form an equalization submodule: Configure n output units and m sets of equalization capacitor networks, where m is a positive integer; each output unit includes a pair of secondary side connection points and an output capacitor. Connect one end of each secondary winding to one of the connection points of the corresponding output unit's pair of secondary side connection points, and connect the other end of each secondary winding to the other connection point of the corresponding output unit's pair of secondary side connection points; connect the output capacitor of each output unit in parallel with a corresponding battery cell, and connect the n battery cells in series to form a battery pack; connect the equalization capacitor network between the corresponding nodes of each output unit to form a charge transfer path between different output units, thereby forming an equalization submodule; the n output units share the power switching network of the preceding circuit, so that energy is transferred to the n output units through k multi-winding transformers and transferred between different battery cells through the equalization capacitor network to achieve voltage equalization between the n series-connected battery cells; Step S4, Layer-by-layer combination and expansion: The battery pack in the equalization submodule is equivalent to a single battery cell to be equalized. At least two equalization submodules are combined and connected through the newly added k' multi-winding transformers and the newly added m' equalization capacitor network to form a higher-level equalization submodule, where k' and m' are both positive integers. Repeat the above combination and expansion steps to construct a multi-layer equalization circuit by expanding it layer by layer.

[0019] This invention provides an active balancing circuit for battery packs based on a multi-transformer balancing submodule, with the following technical advantages: 1) The number of power switching devices is decoupled from the number of series-connected battery cells, significantly reducing circuit complexity, control difficulty, and system cost: In this invention, each output unit shares the same power switching network of the same pre-amplifier circuit. Through the unified high-frequency switching modulation of this power switching network, energy is simultaneously transferred to each output unit via multiple multi-winding transformers. Compared with existing active balancing circuits that configure controllable switches or balancing branches for each individual battery cell, the number of power switching devices and their driving circuits required by this invention does not increase with the number of series-connected battery cells. This directly overcomes the technical problem in existing active balancing circuits where the number of controllable switching devices and their driving and control branches is related to the number of series-connected battery cells, and the circuit complexity, control difficulty, and system cost increase significantly as the number of battery cells increases. The circuit size and control complexity remain essentially unchanged as the number of battery cells in the series increases.

[0020] 2) Replacing a single multi-winding transformer with a large number of secondary windings with a multi-winding transformer with multiple secondary windings reduces the requirements for transformer winding technology and improves engineering feasibility: This invention employs multiple multi-winding transformers, with each primary winding connected in series, parallel, or series-parallel configuration to the primary connection points of the preceding circuit. The sum of the secondary windings of each transformer corresponds to the number of individual battery cells. This method requires fewer windings per transformer, simplifies winding, ensures consistent turns, and easily controls leakage inductance. It overcomes the technical challenges of relying on a single multi-winding transformer for balancing schemes, which require high-precision winding processes and struggle with turns consistency and leakage inductance control. This provides a low-cost and easily manufactured approach for balancing high-series-count battery packs.

[0021] 3) Automatic balancing is achieved by relying on the circuit's own characteristics, resulting in high balancing accuracy and strong operational reliability. This invention establishes a balancing capacitor network between corresponding nodes of each output unit. These capacitors form an automatic charge transfer path between different output units, allowing output units corresponding to battery cells with higher voltage or state of charge to release energy, while output units corresponding to battery cells with lower voltage or state of charge receive replenished energy. This automatically reduces voltage deviations between battery cells and improves balancing accuracy without requiring complex individual cell selection switch arrays and individual cell-by-cell cyclic detection control. Simultaneously, this self-balancing mechanism enhances tolerance to inconsistencies in transformer winding parameters, improving the operational reliability of the balancing circuit.

[0022] 4) The balanced submodules can be combined and expanded layer by layer, possessing good scalability: The equalization circuit of this invention constitutes an equalization submodule, and the battery pack in the submodule can be equivalent to a single battery cell to be equalized. Through the addition of a multi-winding transformer and an additional equalization capacitor network, multiple equalization submodules can be recombined and connected to form a higher-level equalization submodule, and this can be progressively expanded to form a multi-layer equalization circuit. This achieves a significant increase in the number of battery cells without significantly increasing the number of power switching devices, overcoming the technical problem of insufficient scalability of existing equalization circuits and their difficulty in adapting to high-number-cell battery pack applications while maintaining low control complexity and low cost. It can meet the expanded application needs of high-number-cell battery packs at a lower cost.

[0023] 5) Good topology compatibility between front-end and back-end stages, flexible module combination, and wide applicability: The front-end circuit of this invention can adopt various circuit structures such as flyback, forward, full-bridge, half-bridge, and push-pull. The output unit of the rear stage can adopt various circuit structures such as bridge full-wave rectification, isolated Zeta, center-tapped full-wave rectification, and half-wave rectification. The equalizing capacitor network has various basic connection forms, and each form can be combined independently or with each other. The above modules can be arbitrarily combined and matched, and can all achieve automatic output voltage balancing. This invention can adapt to the needs of different voltage levels, power levels, and application occasions, and has wide applicability.

[0024] 6) Active energy transfer is used to achieve energy balance, resulting in high energy utilization: This invention directly transfers energy between individual battery cells through a multi-winding transformer and a balancing capacitor network, instead of consuming excess energy through energy-consuming resistors. This avoids the unnecessary energy loss of passive balancing, improves energy utilization and balancing efficiency, and eliminates the additional heat dissipation pressure when used in large-capacity battery packs. It overcomes the technical problems of passive balancing, which dissipates energy as heat, has low balancing efficiency, and causes heat dissipation pressure in large-capacity applications. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a structural block diagram of the active balancing circuit for a battery pack based on a multi-transformer balancing submodule provided in an embodiment of the present invention.

[0026] Figure 2 This is a circuit diagram of a type II equalizing capacitor network equalizing circuit composed of a dual-tube clamping preamplifier circuit connected in parallel on the primary side of a transformer and a half-wave rectifier structure output unit, as provided in an embodiment of the present invention.

[0027] Figure 3 This is a circuit diagram of a type II equalization capacitor network equalization circuit composed of an asymmetrical half-bridge preamplifier circuit connected in parallel on the primary side of a transformer and an isolated Zeta structure output unit, provided in an embodiment of the present invention.

[0028] Figure 4 This is a circuit diagram of a type II equalizing capacitor network equalizing circuit composed of a full-bridge front-end circuit connected in parallel on the primary side of a transformer and a bridge full-wave rectifier structure output unit, as provided in an embodiment of the present invention.

[0029] Figure 5 This is a circuit diagram of a type II equalizing capacitor network equalizing circuit composed of a push-pull preamplifier circuit connected in series on the primary side of a transformer and a center-tapped full-wave rectifier output unit, as provided in an embodiment of the present invention.

[0030] Figure 6 This is a circuit diagram of a type I equalizing capacitor network equalizing circuit composed of a dual-tube clamping preamplifier circuit connected in series on the primary side of a transformer and a half-wave rectifier structure output unit, as provided in an embodiment of the present invention.

[0031] Figure 7 This is a circuit diagram of a type III equalizing capacitor network equalizing circuit composed of a dual-tube clamping preamplifier circuit connected in series on the primary side of a transformer and a half-wave rectifier structure output unit, as provided in an embodiment of the present invention.

[0032] Figure 8 This is a circuit diagram of an equalization submodule composed of a combination of type I and type III connection equalization capacitor networks provided in an embodiment of the present invention.

[0033] Figure 9 This is a schematic diagram of a multi-level extended structure of a balanced submodule, taking the type I connection method as an example, provided in an embodiment of the present invention.

[0034] Figure 10 This is a circuit diagram of a type II equalizing capacitor network equalizing circuit composed of a dual-tube clamping preamplifier circuit connected in parallel on the primary side of a transformer and a four-way half-wave rectifier output unit, as provided in Embodiment 1 of the present invention.

[0035] Figure 11 This is a circuit diagram of a type II equalizing capacitor network equalizing circuit composed of a dual-tube clamping preamplifier circuit connected in series on the primary side of a transformer and a four-way half-wave rectifier output unit, as provided in Embodiment 2 of the present invention.

[0036] Figure 12 This is a circuit diagram of a multi-level expansion circuit for an equalization submodule, taking the type I connection method as an example, provided in Embodiment 3 of the present invention.

[0037] Figure 13 This is a circuit diagram of an equalization circuit composed of a dual-tube clamping preamplifier circuit and a four-way half-wave rectifier output unit, which is a feature of existing technology.

[0038] Figure 14 This is a simulation diagram of the balancing effect of the balancing circuit of Embodiment 1 of the present invention on a battery pack consisting of four series-connected battery cells.

[0039] Figure 15 This is a simulation diagram of the balancing effect of the balancing circuit of Embodiment 2 of the present invention on a battery pack consisting of four series-connected battery cells.

[0040] Figure 16 yes Figure 13 The diagram shown illustrates the simulation effect of a prior art equalization circuit balancing a battery pack consisting of four series-connected battery cells. This circuit is used in conjunction with... Figure 14 and Figure 15 Compare them.

[0041] Figure 17(a) shows a submodule using a type I equalizing capacitor connection method; Figure 17(b) shows a submodule using a type II equalizing capacitor connection method; Figure 17(c) shows a submodule using a type III equalizing capacitor connection. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0043] (I) Overall Implementation Method: like Figure 1As shown, this embodiment of the invention provides an active balancing circuit for a battery pack based on a multi-transformer balancing submodule, including a front-end circuit, k multi-winding transformers, a back-end circuit, and a battery pack composed of n battery cells connected in series, where k is an integer and 1≤k≤n, and n is an integer and n≥2.

[0044] The front-end circuit includes a DC input terminal, a power switching network, a first primary-side connection point, and a second primary-side connection point. The power switching network includes at least one power switching device, configured to turn the at least one power switching device on and off under the control of a drive signal, performing high-frequency switching modulation on the DC voltage connected to the DC input terminal, and forming a high-frequency pulsating voltage or a high-frequency alternating voltage between the first primary-side connection point and the second primary-side connection point. The front-end circuit can adopt a flyback, forward, full-bridge, half-bridge, or push-pull circuit structure; when the front-end circuit adopts a push-pull circuit structure, the front-end circuit also includes a primary-side center tap connection point.

[0045] Each of the multi-winding transformers includes a primary winding and at least one secondary winding; the primary windings of the k multi-winding transformers form a series, parallel, or series-parallel circuit structure, connected between the first primary connection point and the second primary connection point; the sum of the number of secondary windings of the k multi-winding transformers is n. When all the primary windings of the k multi-winding transformers have a center tap, and two or more of them are connected in series, each primary winding is divided into a first half-winding and a second half-winding with its center tap as the boundary. Each first half-winding is connected in series and then connected between the first primary connection point and the primary center tap connection point. Each second half-winding is connected in series and then connected between the second primary connection point and the primary center tap connection point.

[0046] The subsequent circuit includes n output units and m sets of equalizing capacitor networks, where m is a positive integer. Each output unit includes a pair of secondary connection points and an output capacitor. The two ends of each secondary winding are respectively connected to the pair of secondary connection points of the corresponding output unit. The output capacitor of each output unit is connected in parallel with a corresponding battery cell. The output unit can adopt the following four typical structures: (1) Bridge-type full-wave rectifier structure: r The output unit includes the secondary winding. L Sr rectifier diodes D r1 , D r2 , D r3 and D r4 The rectifier bridge BR r and output capacitor C r ,in r ∈{1,2,…, n};Rectifier diode D r1 Anode-connected rectifier diode D r3 anode, rectifier diode D r1 Cathode connected rectifier diode D r2 anode, rectifier diode D r2 Cathode connected rectifier diode D r4 Cathode, rectifier diode D r3 Cathode connected rectifier diode D r4 anode; secondary winding L Sr The same terminal is connected to the rectifier diode. D r1 cathode and rectifier diode D r2 anode, secondary winding L Sr Non-identical terminals connected to rectifier diodes D r3 cathode and rectifier diode D r4 anode; output capacitor C r The positive terminal is connected to the rectifier diode. D r2 cathode and rectifier diode D r4 Cathode, output capacitor C r The negative terminal is connected to the rectifier diode. D r1 anode and rectifier diode D r3 The anode.

[0047] (2) Isolated Zeta structure: The first r The output unit includes the secondary winding. L Sr Series capacitor C sr rectifier diodes D r Output filter inductor L r and output capacitorC r ,in r ∈{1,2,…, n}; Series capacitor C sr One end is connected to the secondary winding L Sr The same terminal, series capacitor C sr The other end is connected to a rectifier diode. D r Cathode and output filter inductor L r One end; output capacitor C r The positive terminal is connected to the output filter inductor. L r At the other end, the output capacitor C r The negative terminal is connected to the rectifier diode. D r anode and secondary winding L Sr The non-same-name terminal.

[0048] (3) Center-tapped full-wave rectifier structure: r The output unit includes a secondary winding with a center tap. L Sr rectifier diodes D r1 , D r2 and output capacitor C r ,in r ∈{1,2,…, n};Rectifier diode D r1 anode connection secondary winding L Sr The same terminal, rectifier diode D r1 Cathode connected rectifier diode D r2 cathode and output capacitor C r The positive terminal; rectifier diode D r2 anode connection secondary winding L Sr Non-identical terminals, output capacitor C r The negative terminal is connected to the secondary winding. L Sr The center tap.

[0049] (4) Half-wave rectification structure:r The output unit includes the secondary winding. L Sr rectifier diodes D r and output capacitor C r ,in r ∈{1,2,…, n Secondary winding L Sr The same terminal is connected to the rectifier diode. D r anode, rectifier diode D r Cathode connection output capacitor C r The positive terminal and the secondary winding L Sr Connect the output capacitor to the non-identical terminal. C r The negative electrode.

[0050] The equalizing capacitor network includes three basic connection methods: Type I, Type II, and Type III, and their combinations. The Type I connection method involves connecting one equalizing capacitor between corresponding nodes of any two adjacent output units. Each equalizing capacitor network includes... n One equalizing capacitor, number of groups m It is 1 or 2; the Type II connection method is as follows: taking any one output unit's node as a common node, this common node is connected to the corresponding nodes of the remaining output units via a balancing capacitor, and each group of balancing capacitor networks includes n A single balancing capacitor can have different values ​​depending on the location of the common node. m A set of balanced capacitor networks, where 1 ≤ m ≤2( n 1) The Type III connection method is as follows: the corresponding node of each output unit is connected to one end of an equalizing capacitor, and the other end of each equalizing capacitor is connected to the same common point. Each equalizing capacitor network includes... n One equalizing capacitor, number of groups m It can be 1 or 2; m The specific value is determined by the output unit structure adopted by the subsequent circuit. Each of the three basic connection methods mentioned above can be combined independently or with each other to form an equalization submodule.

[0051] The balancing principle of this invention is as follows: n Each output unit shares the power switching network of the preceding circuit. Under the control of the drive signal, the power switching network undergoes high-frequency switching modulation, causing energy to pass through… kA multi-winding transformer transmits power to the subsequent circuit. n Each output unit transfers energy from the primary side to the secondary side to its corresponding output capacitor and battery cell. When energy transfer stops, the equalizing capacitors in the equalizing capacitor network form an energy transfer loop through their respective secondary windings and output capacitors, transferring charge between different output units. This allows the output unit corresponding to a battery cell with a higher voltage or state of charge to release energy, while the output unit corresponding to a battery cell with a lower voltage or state of charge receives replenished energy. After multiple switching cycles, the voltage deviation between the battery cells gradually decreases, achieving... n Voltage self-balancing between individual battery cells connected in series.

[0052] Figures 2-9 Examples of different combinations of front-end circuit topology, transformer primary-side connection method, output unit structure, and equalization capacitor network type are shown: Figure 2 The equalization circuit is a type II equalization capacitor network composed of a dual-tube clamping preamplifier circuit connected in parallel to the primary side of the transformer and a half-wave rectifier structure output unit. Figure 3 The equalization circuit is a type II equalization capacitor network composed of an asymmetrical half-bridge preamplifier circuit connected in parallel with the primary side of the transformer and an isolated Zeta structure output unit. Figure 4 The equalization circuit is a type II equalization capacitor network composed of a full-bridge front-end circuit connected in parallel with the primary side of the transformer and a bridge full-wave rectifier output unit. Figure 5 The equalization circuit is a type II equalization capacitor network composed of a push-pull preamplifier circuit connected in series with the primary side of the transformer and a center-tapped full-wave rectifier output unit. Figure 6 The equalization circuit is a type I equalization capacitor network composed of a dual-tube clamping preamplifier circuit connected in series with the primary side of the transformer and a half-wave rectifier output unit. Figure 7 The equalization circuit is a type III equalization capacitor network composed of a dual-tube clamping preamplifier circuit connected in series with the primary side of the transformer and a half-wave rectifier output unit. Figure 8 This is a circuit that combines type I and type III connection methods of equalizing capacitor networks to form an equalization submodule.

[0053] Furthermore, any of the above-mentioned combinations of equalization circuits can be considered as an equalization submodule, and the battery pack in the equalization submodule can be equivalent to a single battery cell to be equalized; through the addition of k 'Multi-winding transformers and newly added m 'Group of equalized capacitor networks ( k ′、 m (where ' are all positive integers), at least two equalization submodules are combined and connected according to the above Type I, Type II, or Type III connection methods to form a higher-level equalization submodule; repeating the above combination and expansion process, a multi-layer equalization circuit can be formed by expanding layer by layer, such as Figure 9As shown, this enables low-cost, high-string-count battery pack expansion applications.

[0054] (II) Example 1: like Figure 10 As shown, this embodiment provides a scalable active balancing circuit for battery packs based on a multi-transformer primary-side parallel connection and a secondary-side Type II balancing capacitor network. The example uses a dual-tube clamped power switching network in the front-end circuit, a four-output half-wave rectifier structure in the rear-end circuit, and two three-winding transformers connected in parallel on their primary sides. The circuit includes a dual-tube clamped power switching network front-end, two three-winding transformers T1 and T2, a four-output half-wave rectifier structure, and three balancing capacitors C. B1 C B2 C B3 And four lithium-ion battery cells B1, B2, B3, and B4 connected in series. Among them, the four-output half-wave rectifier structure means that each of the four output units adopts a half-wave rectifier structure.

[0055] The front-end of the dual-tube clamping power switch network includes power switches S1 and S2, clamping diodes Dc1 and Dc2, a first primary-side connection point, and a second primary-side connection point. Three-winding transformers T1 and T2 each include one primary winding and two secondary windings. The primary windings of transformers T1 and T2 are connected in parallel between the first and second primary-side connection points. The total number of secondary windings in transformers T1 and T2 is four, denoted as secondary windings. L S1 , L S2 , L S3 and L S4 Secondary winding L S1 , L S2 , L S3 and L S4 They are connected to the four-channel output half-wave rectifier structure respectively.

[0056] The connection configuration of the front-end of the dual-tube clamping power switch network is as follows: DC input source U in The positive terminal is connected to the source of power switch S1 and the cathode of clamping diode Dc1; the source of power switch S1 is connected to the magnetizing inductor. L M1 One end, magnetizing inductor L M2 One end of the clamping diode Dc2, the cathode of the clamping diode Dc2, and the corresponding terminals of the primary windings of the three-winding transformers T1 and T2; the drain of the power switch S2 is connected to the magnetizing inductor.L M1 The other end, the magnetizing inductor L M2 The other end, the anode of clamping diode Dc1, and the non-identical terminals of the primary windings of three-winding transformers T1 and T2; the source of power switch S2 and the anode of clamping diode Dc2 are connected to the DC input source. U in The negative electrode.

[0057] The four-output half-wave rectifier structures have the same connection configuration. The first output half-wave rectifier structure includes a secondary winding. L S1 rectifier diode D1 and output capacitor C 1. Secondary winding L S1 The same-name terminal is connected to the anode of rectifier diode D1, and the cathode of rectifier diode D1 is connected to the output capacitor. C 1's positive terminal and secondary winding L S1 Connect the output capacitor to the non-identical terminal. C The negative terminal of 1; the second output half-wave rectifier structure includes the secondary winding. L S2 rectifier diode D2 and output capacitor C 2. The third-path output half-wave rectifier structure includes the secondary winding. L S3 rectifier diode D3 and output capacitor C 3. The fourth output half-wave rectifier structure includes the secondary winding. L S4 rectifier diode D4 and output capacitor C 4. The connection method of the second to fourth output half-wave rectifier structure is the same as that of the first channel.

[0058] Equalizing capacitor C B1 , C B2 , C B3 One end of the winding is connected to the secondary winding in the first output half-wave rectifier structure. L S1 The connection node formed by the same-name terminal of the rectifier diode D1 and the anode of the rectifier diode D1; balancing capacitor. C B1 The other end is connected to the secondary winding in the second output half-wave rectifier structure. L S2 The connection node formed by the same-name terminal of the rectifier diode D2 and the anode of the rectifier diode D2; balancing capacitor. C B2 The other end is connected to the secondary winding in the third output half-wave rectifier structure.L S3 The connection node formed by the same-name terminal of the rectifier diode D3 and the anode of the rectifier diode D3; balancing capacitor. C B3 The other end is connected to the secondary winding in the fourth output half-wave rectifier structure. L S4 The connection node is formed between the same-name terminal of the rectifier diode D4 and the anode of the rectifier diode D4. The four battery cells B1, B2, B3, and B4 are connected in series. The positive terminal of battery cell B1 is connected to the output capacitor. C The positive terminal of cell B1 is connected to the cathode of rectifier diode D1, and the negative terminal of cell B1 is connected to the output capacitor. C 1's negative and secondary windings L S1 The non-identical terminals and the positive terminal of battery cell B2; the positive terminal of battery cell B2 is connected to the output capacitor. C The positive terminal of cell B2 is connected to the cathode of rectifier diode D2, and the negative terminal of cell B2 is connected to the output capacitor. C 2's negative and secondary windings L S2 The non-identical terminals and the positive terminal of battery cell B3; the positive terminal of battery cell B3 is connected to the output capacitor. C The positive terminal of cell B3 and the cathode of rectifier diode D3 are connected, and the negative terminal of cell B3 is connected to the output capacitor. C 3 negative and secondary windings L S3 The non-identical terminals and the positive terminal of battery cell B4; the positive terminal of battery cell B4 is connected to the output capacitor. C The positive terminal of cell B4 and the cathode of rectifier diode D4 are connected, and the negative terminal of cell B4 is connected to the output capacitor. C 4 negative and secondary windings L S4 The non-same-name terminal.

[0059] The working principle of this embodiment is as follows: Within one switching cycle, when the primary winding current of the three-winding transformers T1 and T2 flows in from the same-name terminal, energy is transferred from the primary side to the secondary side through the three-winding transformers T1 and T2. L S1 , L S2 , L S3 , L S4 The voltage induced causes rectifier diodes D1, D2, D3, and D4 to conduct, and is then supplied to the output capacitor. C 1. C 2. C 3. C4. Energy is transferred to the corresponding battery cells B1, B2, B3, and B4. When the primary winding current of the three-winding transformers T1 and T2 flows out from the same-name terminal, energy transfer from the primary to the secondary side stops, and rectifier diodes D1, D2, D3, and D4 are cut off. At this time, the equalization capacitor... C B1 , C B2 , C B3 It can form an energy transfer circuit through the secondary winding and the output capacitor.

[0060] Specifically, the equalization capacitor C B1 Able to pass through the equalization capacitor C B1 Secondary winding L S1 Output capacitor C 2 and secondary winding L S2 The circuit formed transfers charge with the second output unit; equalization capacitor. C B2 It can transfer charge with the third output unit through the relevant secondary winding and output capacitor; equalization capacitor C B3 It can transfer charge with the fourth output unit through the relevant secondary winding and output capacitor.

[0061] Through the aforementioned equalizing capacitor network, an automatic charge transfer path is formed between different output units, enabling the output unit corresponding to the higher voltage battery cell to release some energy, while the output unit corresponding to the lower voltage battery cell receives supplemental energy, thereby reducing the voltage deviation between the four series-connected battery cells.

[0062] If the state of charge (SOC) of individual cells in the battery pack differs, for example, if cell B1 has a higher SOC than cells B2, B3, and B4, then the balancing capacitor will... C B1 , C B2 , C B3 It can transfer charge between different output units, allowing energy to be preferentially transferred to battery cells with lower voltage or state of charge. After multiple switching cycles, the voltage deviation between battery cells B1, B2, B3, and B4 gradually decreases, ultimately achieving self-balancing of the battery pack.

[0063] (III) Example 2: like Figure 11As shown, this embodiment provides a scalable active balancing circuit for battery packs based on a multi-transformer primary-side series connection and a secondary-side type II balancing capacitor network. The example uses a dual-tube clamped power switch network in the front-end circuit, a four-output half-wave rectifier structure in the rear-end circuit, and two three-winding transformers connected in series on their primary sides. The circuit includes a dual-tube clamped power switch network front-end, two three-winding transformers T1 and T2, a four-output half-wave rectifier structure, and three balancing capacitors. C B1 , C B2 , C B3 And four lithium-ion battery cells B1, B2, B3, and B4 connected in series.

[0064] The difference between this embodiment and Embodiment 1 lies in the connection method of the primary windings of the three-winding transformers T1 and T2 and the configuration of the magnetizing inductor: the same-name terminal of the primary winding of the three-winding transformer T1 is connected to the first primary connection point; the non-same-name terminal of the primary winding of the three-winding transformer T1 is connected to the same-name terminal of the primary winding of the three-winding transformer T2; and the non-same-name terminal of the primary winding of the three-winding transformer T2 is connected to the second primary connection point. That is, the primary windings of the three-winding transformers T1 and T2 are connected in series between the first and second primary connection points. The connection form of the front-end of the dual-tube clamping power switch network is: DC input source... U in The positive terminal of power switch S2 is connected to the drain of power switch S1 and the cathode of clamping diode Dc1; the source of power switch S1 is connected to one end of magnetizing inductor LM1, the cathode of clamping diode Dc2, and the same-name terminal of the primary winding of three-winding transformer T1; the drain of power switch S2 is connected to one end of magnetizing inductor LM2, the anode of clamping diode Dc1, and the non-same-name terminal of the primary winding of three-winding transformer T2; the source of power switch S2 and the anode of clamping diode Dc2 are connected to the DC input source. U in The negative terminal of the magnetizing inductor LM1 is connected to the other end of the magnetizing inductor LM2.

[0065] The four-output half-wave rectifier structure, the type II equalizing capacitor network, and the connection form of the four battery cells in this embodiment are the same as those in Embodiment 1, and will not be repeated here.

[0066] The working principle of this embodiment is the same as that of Embodiment 1: Within one switching cycle, when the primary winding current of the three-winding transformers T1 and T2 connected in series on the primary side flows in from the same terminal, energy is transferred from the primary side to the secondary side through the three-winding transformers T1 and T2. L S1 , L S2 , LS3 , L S4 The voltage induced causes rectifier diodes D1, D2, D3, and D4 to conduct, and is then supplied to the output capacitor. C 1. C 2. C 3. C 4. Energy transfer between the corresponding battery cells; when the primary winding current flows out from the same terminal, energy transfer from the primary to the secondary side stops, rectifier diodes D1, D2, D3, and D4 are cut off, and the equalization capacitor... C B1 , C B2 , C B3 An energy transfer circuit is formed by the secondary winding and the output capacitor, enabling charge transfer between different output units. After multiple switching cycles, the voltage deviation between the four battery cells gradually decreases, ultimately achieving self-balancing of the battery pack.

[0067] Figure 14 and Figure 15 Simulation results of balancing a battery pack consisting of four series-connected battery cells using the balancing circuits of Examples 1 and 2, respectively. Figure 16 for Figure 13 The simulation results of the prior art equalization circuit are shown. A comparison reveals that the circuits of Embodiments 1 and 2 of this invention can achieve equalization effects comparable to those of prior art circuits without increasing the number of power switching devices as the number of battery cells increases, and they also possess the capability for layer-by-layer expansion.

[0068] (iv) Example 3: like Figure 12 As shown, this embodiment provides a two-layer equalization circuit expansion method based on multiple equalization sub-modules employing half-wave rectifier output units and type I equalization capacitor networks. Multi-layer equalization circuits derived from the combined expansion method of this invention include, but are not limited to, this embodiment. This embodiment uses a dual-tube clamped power switch network in the front-end circuit, a 12-channel output half-wave rectifier structure in the rear-end circuit, and four four-winding transformers connected in parallel on their primary sides as an example. The circuit includes a dual-tube clamped power switch network front-end, four four-winding transformers T0, T1, T2, T3, ... 12 Output half-wave rectifier structure, 8 equalization capacitors C B01 , C B02 , C B11 , C B12 , C B21 , C B22, C B31 , C B32 And 9 lithium-ion battery cells B connected in series 11 B 12 B 13 B 21 B 22 B 23 B 31 B 32 B 33 .

[0069] The front-end of the dual-tube clamping power switch network includes a power switch S1, clamping diodes Dc1 and Dc2, a first primary-side connection point, and a second primary-side connection point. Four-winding transformers T0, T1, T2, and T3 each include one primary winding and three secondary windings. The primary windings of the four-winding transformers T0, T1, T2, and T3 are connected in parallel between the first and second primary-side connection points. The total number of secondary windings in the four four-winding transformers is 12, denoted as secondary windings. L S01 , L S02 , L S03 , L S11 , L S12 , L S13 , L S21 , L S22 , L S23 , L S31 , L S32 , L S33 These are connected to a 12-channel output half-wave rectifier structure. The three secondary windings of the four-winding transformer T0, along with its corresponding three-channel output half-wave rectifier structure and two balancing capacitors, constitute a balancing submodule, denoted as submodule 0. Four-winding transformers T1, T2, and T3 respectively constitute submodules 1, 2, and 3. Submodules 1, 2, and 3 use a single battery cell as the balancing object, while submodule 0 uses battery cell B as the balancing object. 11 B 12 B 13 The battery pack consists of individual battery cells B. 21 B 22 B 23 The battery pack consists of the battery cells B. 31 B32 B 33 The battery packs are used for balancing.

[0070] The connection configuration of the front-end of the dual-tube clamping power switch network is as follows: DC input source U in The positive terminal of power switch S2 is connected to the drain of power switch S1 and the cathode of clamping diode Dc1; the source of power switch S1 is connected to one end of magnetizing inductor LM1, one end of magnetizing inductor LM2, the cathode of clamping diode Dc2, and the same-name terminals of the primary windings of four-winding transformers T0, T1, T2, and T3; the drain of power switch S2 is connected to the other end of magnetizing inductor LM1, the other end of magnetizing inductor LM2, the anode of clamping diode Dc1, and the non-same-name terminals of the primary windings of four-winding transformers T0, T1, T2, and T3; the source of power switch S2 and the anode of clamping diode Dc2 are connected to the DC input source. U in The negative electrode.

[0071] In the 12-channel output half-wave rectifier structure, submodules 0, 1, 2, and 3 have the same connection configuration. Taking submodule 0 as an example: the first output half-wave rectifier structure includes a secondary winding. L S01 1 Rectifier diode D 01 and output capacitor C 01 Secondary winding L S01 The same terminal is connected to the rectifier diode D. 01 The anode of the rectifier diode D 01 Cathode connection output capacitor C 01 The positive terminal and the secondary winding L S01 Connect the output capacitor to the non-identical terminal. C 01 The negative terminal; the second output half-wave rectifier structure includes the secondary winding. L S02 1 Rectifier diode D 02 and output capacitor C 02 The third-output half-wave rectifier structure includes a secondary winding. L S03 1 Rectifier diode D 03 and output capacitor C 03 Its connection method is the same as the first path. The three-output half-wave rectifier structure of submodule 1 includes secondary windings. L S11 , L S12 ,L S13 rectifier diode D 11 D 12 D 12 D 13 and output capacitor C 11 , C 12 , C 13 The three-output half-wave rectifier structure of submodule 2 includes secondary windings. L S21 , L S22 , L S23 rectifier diode D 21 D 22 D 23 and output capacitor C 21 , C 22 , C 23 The three-output half-wave rectifier structure of submodule 3 includes secondary windings. L S31 , L S32 , L S33 rectifier diode D 31 D 32 D 33 and output capacitor C 3. C 32 , C 33 The connection form of each output half-wave rectifier structure in submodule 1, submodule 2, and submodule 3 is the same as that in submodule 0.

[0072] The eight balancing capacitors are divided into four groups, meaning each submodule has one type I balancing capacitor network, and each group includes two balancing capacitors. For submodule 0: balancing capacitors... C B01 One end is connected to the secondary winding L S01 The same terminal as the rectifier diode D 01 The connection node formed by the anode, equalizing capacitance C B01 The other end is connected to the secondary winding. L S02 The same terminal as the rectifier diode D 02 The connection node formed by the anode; equalizing capacitor C B02One end is connected to the secondary winding L S02 The same terminal as the rectifier diode D 02 The connection node formed by the anode, equalizing capacitance C B02 The other end is connected to the secondary winding. L S03 The same terminal as the rectifier diode D 03 The connection node formed by the anode. For submodule 1, the equalizing capacitor... C B11 Connected to the secondary winding L S11 , L S12 Between corresponding nodes, equalization capacitance C B12 Connected to the secondary winding L S12 , L S13 Between corresponding nodes; for submodule 2, equalizing capacitors C B2 Connected to the secondary winding L S21 , L S22 Between corresponding nodes, equalization capacitance C B22 Connected to the secondary winding L S22 , L S23 Between corresponding nodes; for submodule 3, equalizing capacitors C B31 Connected to the secondary winding L S31 , L S32 Between corresponding nodes, equalization capacitance C B32 Connected to the secondary winding L S32 , L S33 Between corresponding nodes; the specific connection nodes of the balancing capacitors in submodules 1, 2, and 3 are the same as those in submodule 0.

[0073] 9 battery cells B 11 B 12 B 13 B 21 B 22 B 23 B 31 B 32 B 33They are connected in series sequentially. For submodules 1, 2, and 3, the battery cell B... 11 B 12 B 13 respectively with the output capacitor C 11 , C 12 , C 13 Parallel connection, battery cell B 21 B 22 B 23 respectively with the output capacitor C 21 , C 22 , C 23 Parallel connection, battery cell B 31 B 32 B 33 respectively with the output capacitor C 31 , C 32 , C 33 The rectifier diodes are connected in parallel, and the cathodes of the output half-wave rectifier structure are connected to the positive terminal of the corresponding battery cell. For submodule 0, the output capacitor... C 01 , C 02 , C 03 Respectively with battery cell B 11 B 12 B 13 The battery pack and battery cells B are composed of 21 B 22 B 23 The battery pack and battery cells B are composed of 31 B 32 B 33 The battery packs are connected in parallel, and the cathodes of the rectifier diodes with the half-wave rectifier structure are connected to the positive terminals of the corresponding battery packs.

[0074] The working principle of this embodiment is as follows: During one switching cycle, when the primary winding current of the four-winding transformers T0, T1, T2, and T3 flows in from the same-name terminal, energy is transferred from the primary side to the secondary side through the four-winding transformers T0, T1, T2, and T3. Each secondary winding induces a voltage that turns on the corresponding rectifier diode and transfers energy to each output capacitor and the corresponding battery cell or battery pack. When the primary winding current flows out from the same-name terminal, energy stops being transferred from the primary side to the secondary side, and each rectifier diode in the 12-channel output half-wave rectifier structure is turned off. At this time, each equalizing capacitor can form an energy transfer circuit through the corresponding secondary winding and output capacitor.

[0075] This embodiment employs a two-layer equalization structure: In the first layer, submodules 1, 2, and 3 achieve voltage equalization among the three individual cells within each battery pack through their respective Type I equalization capacitor networks; in the second layer, submodule 0 treats each of the three battery packs as a single cell to be equalized, achieving voltage equalization among the three battery packs through its Type I equalization capacitor network. If there are differences in the state of charge of the individual cells, for example, cell B... 11 If the state of charge (SPC) of a cell is higher than that of the other cells, then during multiple switching cycles, the balancing capacitors can transfer charge between different output cells, preferentially transferring energy to cells with lower voltage or SPC. After multiple switching cycles, the voltage deviation between the nine cells gradually decreases, ultimately achieving layer-by-layer self-balancing of the battery pack.

Claims

1. A battery pack active balancing circuit based on a multi-transformer balancing submodule, characterized in that... The equalization circuit includes: The circuit consists of a front-end circuit, k multi-winding transformers, a back-end circuit, and a battery pack composed of n battery cells connected in series, where: k is an integer and 2≤k≤n, and n is an integer and n≥2; The front-end circuit includes a DC input terminal, a power switching network, a first primary-side connection point, and a second primary-side connection point. The two ends of the DC input terminal are used to connect to the two poles of the DC input source. One end of the power switch network is connected to the DC input terminal, and the other end of the power switch network is connected to the first primary side connection point and the second primary side connection point. The front-end circuit is used to perform high-frequency switching modulation of the DC voltage at the DC input terminal through a power switching network, forming a high-frequency pulsating voltage or a high-frequency alternating voltage between the first primary-side connection point and the second primary-side connection point. Each multi-winding transformer includes one primary winding and at least one secondary winding; the primary windings of k multi-winding transformers form a series, parallel, or series-parallel circuit structure, one end of which is connected to a first primary connection point, and the other end of which is connected to a second primary connection point; the sum of the number of secondary windings of the k multi-winding transformers is n; The subsequent circuit includes n output units and m sets of equalizing capacitor networks, where m is a positive integer; each output unit includes a pair of secondary side connection points and an output capacitor; the output unit is used to rectify the high-frequency voltage output from the corresponding secondary winding into a DC voltage; One end of each secondary winding is connected to one of the two secondary connection points of the corresponding output unit, and the other end of each secondary winding is connected to the other connection point of the two secondary connection points of the corresponding output unit. One terminal of the output capacitor of each output unit is connected to one terminal of the corresponding battery cell, and the other terminal of the output capacitor is connected to the other terminal of the corresponding battery cell. The equalizing capacitor network is connected between corresponding nodes of each output unit to form charge transfer paths between different output units; Each of the n battery cells corresponds to one of the n output units, and the n output units share the power switching network of the front-end circuit. Energy is transferred to the back-end circuit through k multi-winding transformers and then transferred between different battery cells through the equalizing capacitor network to achieve voltage balance among the n series-connected battery cells.

2. The active balancing circuit for a battery pack based on a multi-transformer balancing submodule according to claim 1, characterized in that: The power switching network includes at least one power switching device, and the power switching network is configured to turn on and off the at least one power switching device under the control of a drive signal to perform high-frequency switching modulation on the DC voltage connected to the DC input terminal. The front-end circuit is a flyback, forward, full-bridge, half-bridge, or push-pull circuit structure. When the front-end circuit adopts a push-pull circuit structure, the front-end circuit also includes a primary-side center tap connection point. The power switching network forms a high-frequency pulsating voltage or a high-frequency alternating voltage between the first primary-side connection point and the primary-side center tap connection point, and between the second primary-side connection point and the primary-side center tap connection point.

3. The active balancing circuit for a battery pack based on a multi-transformer balancing submodule according to claim 2, characterized in that: When all k primary windings of the multi-winding transformer are provided with center taps, and two or more of the k primary windings are connected in series, each primary winding is divided into a first half-winding and a second half-winding with its center tap as the boundary; the first half-windings of each primary winding are connected in series in sequence and then connected between the first primary winding connection point and the primary center tap connection point; the second half-windings of each primary winding are connected in series in sequence and then connected between the second primary winding connection point and the primary center tap connection point.

4. The active balancing circuit for a battery pack based on a multi-transformer balancing submodule according to claim 3, characterized in that: The m-group equalization capacitor network includes three basic connection methods: Type I, Type II, and Type III, and their combinations; Type I connection method is as follows: connect a balancing capacitor between the corresponding nodes of any two adjacent output units. Each balancing capacitor network includes n-1 balancing capacitors, where m is 1 or 2. Type II connection method: Any node of an output unit is used as a common node. This common node is connected to the corresponding nodes of the remaining output units via a balancing capacitor. Each balancing capacitor network includes n-1 balancing capacitors, where m is an integer and 1 ≤ m ≤ 2(n...). 1); The Type III connection method is as follows: the corresponding node of each output unit is connected to one end of a balancing capacitor, and the other end of each balancing capacitor is connected to the same common point. Each balancing capacitor network includes n balancing capacitors, where m is 1 or 2.

5. The active balancing circuit for a battery pack based on a multi-transformer balancing submodule according to claim 4, characterized in that: The output unit is a bridge full-wave rectifier structure, and the r-th output unit includes a secondary winding. L Sr 1. By rectifier diode D r1 1 Rectifier diode D r2 1 Rectifier diode D r3 and rectifier diode D r4 The rectifier bridge BR r and output capacitor C r Where r∈{1,2,…,n}; The rectifier diode D r1 The anode of the rectifier diode D is connected. r3 The anode of the rectifier diode D r1 The cathode is connected to the rectifier diode D r2 The anode of the rectifier diode D r2 The cathode is connected to the rectifier diode D r4 The cathode, the rectifier diode D r3 The cathode is connected to the rectifier diode D r4 anode; The secondary winding L Sr The same terminal is connected to the rectifier diode D. r1 Cathode and rectifier diode D r2 The anode, the secondary winding L Sr The non-identical terminal is connected to the rectifier diode D. r3 Cathode and rectifier diode D r4 anode; The output capacitor C r The positive terminal is connected to the rectifier diode D. r2 Cathode and rectifier diode D r4 The cathode, the output capacitor C r The negative terminal is connected to the rectifier diode D. r1 anode and rectifier diode D r3 The anode.

6. The active balancing circuit for a battery pack based on a multi-transformer balancing submodule according to claim 5, characterized in that: The output unit is an isolated Zeta structure, and the r-th output unit includes a secondary winding. L Sr Series capacitor C sr 1 Rectifier diode D r Output filter inductor L r and output capacitor C r , where r∈{1,2,…,n}; The series capacitor C sr One end is connected to the secondary winding L Sr The same terminal, the series capacitor C sr The other end is connected to rectifier diode D r Cathode and output filter inductor L r One end; The output capacitor C r The positive terminal is connected to the output filter inductor. L r At the other end, the output capacitor C r The negative terminal is connected to the rectifier diode D. r anode and secondary winding L Sr The non-same-name terminal.

7. The active balancing circuit for a battery pack based on a multi-transformer balancing submodule according to claim 6, characterized in that: The output unit is a center-tapped full-wave rectifier structure, and the r-th output unit includes a secondary winding with a center tap. L Sr 1 Rectifier diode D r1 1 Rectifier diode D r2 and output capacitor C r , where r∈{1,2,…,n}; The rectifier diode D r1 The anode is connected to the secondary winding. L Sr The rectifier diode D is located at the same terminal. r1 The cathode is connected to the rectifier diode D r2 The cathode and the output capacitor C r The positive electrode; The rectifier diode D r2 The anode is connected to the secondary winding. L Sr The output capacitor is a non-identical terminal. C r The negative terminal is connected to the center tap of the secondary winding LSR.

8. The active balancing circuit for a battery pack based on a multi-transformer balancing submodule according to claim 7, characterized in that: The output unit is a half-wave rectifier structure, the first... i The output unit includes the secondary winding. L Si 1 Rectifier diode D i and output capacitor C i ,in i ∈{1,2,…,n}; The secondary winding L Si The same terminal is connected to the rectifier diode D. i The anode of the rectifier diode D i Cathode connection output capacitor C i The positive terminal, the secondary winding L Si Connect the output capacitor to the non-identical terminal. C i The negative electrode; No. i Individual battery cell B i The positive terminal connection i Output capacitor in the output unit C i The positive terminal and the rectifier diode D i The cathode, the first i Individual battery cell B i The negative terminal connection i Output capacitor in the output unit C i negative and secondary windings L Si The non-same-name ends, where i∈{1,2,…,n}.

9. The active balancing circuit for a battery pack based on a multi-transformer balancing submodule according to claim 8, characterized in that: The battery pack active balancing circuit constitutes a balancing submodule, and the battery pack in the balancing submodule is equivalent to a single battery to be balanced; the balancing submodule is connected to at least one other balancing submodule through the newly added k' multi-winding transformers and the newly added m' balancing capacitor network, and expands layer by layer to form a multi-layer balancing circuit, where k' and m' are both positive integers.

10. A method for combining and expanding the active balancing circuit of a battery pack based on a multi-transformer balancing submodule, characterized in that: Includes the following steps: Step S1: Configure the front-end circuit: The front-end circuit includes a DC input terminal, a power switch network, a first primary-side connection point, and a second primary-side connection point. One end of the power switch network is connected to the DC input terminal, and the other end of the power switch network is connected to the first primary-side connection point and the second primary-side connection point, so that the front-end circuit performs high-frequency switching modulation on the DC voltage connected to the DC input terminal through the power switch network, forming a high-frequency pulsating voltage or a high-frequency alternating voltage between the first primary-side connection point and the second primary-side connection point. Step S2: Configure k multi-winding transformers: Each multi-winding transformer includes one primary winding and at least one secondary winding. The primary windings of the k multi-winding transformers are arranged in series, parallel, or series-parallel circuit structures. One end of the series, parallel, or series-parallel circuit structure is connected to the first primary winding connection point, and the other end of the series, parallel, or series-parallel circuit structure is connected to the second primary winding connection point. The sum of the number of secondary windings of the k multi-winding transformers is n, where k is an integer and 1≤k≤n, and n is an integer and n≥2. Step S3: Configure the subsequent circuit and combine it to form an equalization submodule: Configure n output units and m sets of equalization capacitor networks, where m is a positive integer; each output unit includes a pair of secondary side connection points and an output capacitor. Connect one end of each secondary winding to one of the connection points of the corresponding output unit's pair of secondary side connection points, and connect the other end of each secondary winding to the other connection point of the corresponding output unit's pair of secondary side connection points; connect the output capacitor of each output unit in parallel with a corresponding battery cell, and connect the n battery cells in series to form a battery pack; connect the equalization capacitor network between the corresponding nodes of each output unit to form a charge transfer path between different output units, thereby forming an equalization submodule; the n output units share the power switching network of the preceding circuit, so that energy is transferred to the n output units through k multi-winding transformers and transferred between different battery cells through the equalization capacitor network to achieve voltage equalization between the n series-connected battery cells; Step S4, Layer-by-layer combination and expansion: The battery pack in the equalization submodule is equivalent to a single battery cell to be equalized. At least two equalization submodules are combined and connected through the newly added k' multi-winding transformers and the newly added m' equalization capacitor network to form a higher-level equalization submodule, where k' and m' are both positive integers. Repeat the above combination and expansion steps to construct a multi-layer equalization circuit by expanding it layer by layer.

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