Energy storage device and energy balancing method

Abstract

The invention relates to an energy storage device and an energy balancing method, and the energy storage device comprises at least two battery packs, each battery pack comprises at least two single batteries; at least one in-pack equalization circuit configured in each battery pack, wherein the in-pack equalization circuit is used for equalizing energy among each single battery in the pack; at least one inter-group equalization circuit configured between the at least two battery packs, wherein the inter-group equalization circuit is used for equalizing energy between the battery packs; the invention discloses a battery state collector, a driving circuit and a controller. The invention provides an intra-group and inter-group equalization topology circuit, and the intra-group equalization topology is a topology combining a double-layer selection switch and a Cuk equalization circuit, and can equalize the energy between any single batteries in the group. The inter-pack equalization topology is a Buck-Boost-based topology, and can equalize energy between adjacent battery packs.

Description

Technical Field

[0001] The present invention relates to the field of battery energy, and specifically relates to an energy storage device and an energy balancing method. Background Art

[0002] From portable gadgets to electric vehicles and renewable energy systems, batteries have become essential in the wide application of energy storage and electrification. In specific use, multiple batteries are often combined into a battery pack through a specific connection method for use. Therefore, the effectiveness, performance, and lifespan of the battery pack have become the focus of current improvement and optimization.

[0003] The state of the battery pack is actually closely related to each individual battery in the battery pack. On the one hand, due to the influence of production processes, there are certain differences in performance indicators such as the initial capacity, equivalent internal impedance, and self-discharge rate of individual batteries; on the other hand, the initial state differences of individual batteries will accumulate with countless charge and discharge cycles. The voltage or SOC imbalance of individual batteries will affect the rechargeable capacity and dischargeable capacity of the battery pack, resulting in a reduction in the overall available capacity and a shortening of the service life of the battery pack. Therefore, it is necessary to study an efficient balancing method for battery monomers in the battery pack.

[0004] To ensure the consistency of charging and discharging characteristics, balancing refers to the process of balancing the charge energy of each individual battery in the battery pack. The purpose of individual battery balancing is to extend the service life of the battery pack, improve energy utilization efficiency, and ensure the safety of the entire battery pack. There are various methods for individual battery balancing, including passive balancing that releases extra energy in the form of heat, and active balancing that moves energy between individual batteries. Figure 1 Schematic diagrams of the balancing effects provided by the prior art. Figure 1 Show two effects of active balancing and passive balancing. As Figure 1 can be seen, passive balancing usually has a low energy utilization efficiency. In addition, the heat generated during the balancing process may lead to thermal runaway. The active balancing scheme transfers unbalanced energy between batteries based on different "peak shaving and valley filling" methods, and uses energy storage components such as inductors and capacitors to regulate the flow of energy to maintain the charge balance state between batteries. This method usually has a higher energy utilization efficiency. Active balancing technologies can be divided into four different categories according to their charge transfer methods: individual battery to individual battery method, battery pack to battery pack method, individual battery to battery pack method, and battery pack to individual battery method.

[0005] The implementation of the battery-to-battery pack method can use either a single transformer or multiple transformers. However, due to the large requirements for MOSFETs and gate drivers, this method requires a high cost, resulting in a relatively slow balancing process. The battery pack-to-battery pack method can be implemented through a multi-output transformer or multiple transformers. Compared with the battery-to-battery pack method, this method involves fewer switches. However, the battery pack-to-battery pack method requires a larger number of transformers, making its design complex and costly. The combination of the two methods, called the battery-battery pack-battery method, provides a faster balancing speed. However, this method requires a large number of optocouplers to drive the bidirectional switches and requires the use of two DC-DC converters, making it complex and expensive to implement. Summary of the Invention

[0006] Based on the above description, the present invention provides an energy storage device and an energy balancing method to solve the safety problems and premature failures such as capacity and efficiency degradation caused by the imbalance of the SOC of individual batteries.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: An energy storage device, comprising:

[0008] At least two battery packs, each battery pack including at least two individual batteries;

[0009] At least one intra-pack balancing circuit configured in each of the battery packs, the intra-pack balancing circuit being used to balance the energy between individual batteries within the pack;

[0010] At least one inter-pack balancing circuit configured between at least two of the battery packs, the inter-pack balancing circuit being used to balance the energy between the battery packs;

[0011] A battery state collector, a controller, and a drive circuit;

[0012] The battery state collector is used to collect the energy states of individual batteries and the energy states of the battery packs, and send the energy states of the individual batteries and the energy states of the battery packs to the controller;

[0013] The controller is used to receive the energy states of individual batteries and the energy states of the battery packs sent by the battery state collector, and send a drive instruction to the drive circuit;

[0014] The drive circuit is used to receive the drive instruction from the controller and drive the intra-pack balancing circuit and the inter-pack balancing circuit to work according to the drive instruction.

[0015] Further, the intra-pack balancing circuit is configured with a balancing control circuit and at least two upper switches and at least two lower switches correspondingly connected to the individual batteries;

[0016] The upper switch and the lower switch form a charge and discharge loop with the equalization control circuit;

[0017] The equalization control circuit controls the charge and discharge loop to perform charge and discharge according to the driving instruction.

[0018] Further, the equalization control circuit controls the charge and discharge loop to perform charge and discharge according to the driving instruction, which specifically includes:

[0019] The battery state collector confirms that there is currently a single battery in a high energy state and a single battery in a low energy state. The controller sends a driving instruction to the driving circuit, and the driving circuit drives the equalization control circuit to control the charge and discharge loop to perform charge and discharge according to the driving instruction.

[0020] Further, the equalization control circuit includes:

[0021] A first inductor and a first conduction element;

[0022] The first inductor, the first conduction element and the high energy state single battery form a first loop;

[0023] A second inductor and a first capacitor;

[0024] The second inductor, the first capacitor and the low energy state single battery form a second loop;

[0025] The first loop and the second loop are externally connected to the driving circuit;

[0026] The first loop is used to control the high energy state single battery to discharge and store in the first inductor according to the drive of the driving circuit;

[0027] The second loop is used to control the first capacitor to discharge according to the drive of the driving circuit, and the second inductor charges the low energy state single battery.

[0028] Further, the current change during the controller drive control is:

[0029]

[0030] where, I L1 is the average current passing through the first inductor, I L2 is the average current passing through the second inductor, Vc is the capacitor voltage, V B1 and V Bi are respectively the high energy state single battery voltage and the high energy state single battery cell voltage connected to the cuk circuit, D is the duty cycle, and Ts is the switching period.

[0031] Further, the equalization control circuit further includes:

[0032] A second conducting element;

[0033] The first capacitor, the first inductor and the high-energy state single battery form a third loop;

[0034] The second inductor, the second conducting element and the low-energy state single battery form a fourth loop;

[0035] The third loop and the fourth loop are externally connected to the drive circuit;

[0036] The third loop is used to control the discharge of the first inductor and the high-energy state single battery according to the drive of the drive circuit, and charge the first capacitor;

[0037] The fourth loop is used to control the charging of the low-energy state single battery by the second inductor according to the drive of the drive circuit.

[0038] Further, the inter-group equalization circuit is configured as a buck-boost circuit, and the buck-boost circuit includes:

[0039] A third conducting element and a third inductor;

[0040] The third conducting element, the third inductor and the high-energy battery pack form a fifth loop;

[0041] The fifth loop is externally connected to the drive circuit;

[0042] The fifth loop is used to control the discharge of the high-energy battery pack according to the drive of the drive circuit and charge the third inductor.

[0043] Further, the buck-boost circuit further includes:

[0044] A fourth conducting element, and the fourth conducting element, the third inductor and the low-energy battery pack form a sixth loop;

[0045] The sixth loop is externally connected to the drive circuit;

[0046] The sixth loop is used to control the discharge of the third inductor according to the drive of the drive circuit and charge the low-energy battery pack.

[0047] Further, the buck-boost circuit is further configured with:

[0048] A demagnetization circuit, which demagnetizes the third inductor after the battery pack with high average energy completes the discharge process and after the battery pack with low average energy finishes charging.

[0049] On the other hand, the present invention also provides an energy balancing method, including:

[0050] Detect and confirm the high-energy-state single cells and low-energy-state single cells in the battery pack;

[0051] Based on the in-group balancing circuit, control the high-energy-state single cells to discharge and transfer the energy to the low-energy-state single cells;

[0052] Detect and confirm the average energy between battery packs, and based on the inter-group balancing circuit, control the battery pack with higher average energy to discharge and transfer the energy to the battery pack with lower average energy.

[0053] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects: The present invention provides an in-group and inter-group balancing topology circuit. The in-group balancing topology is a topology that combines a double-layer selection switch and a Cuk balancing circuit, which can balance the energy between any single cells in the group. The inter-group balancing topology is a topology based on Buck-Boost, which can balance the energy between adjacent battery packs. Description of the Drawings

[0054] Figure 1 is a schematic diagram of the balancing effect provided by the prior art;

[0055] Figure 2 is a schematic diagram of the structure of the energy storage device provided by the embodiment of the present invention;

[0056] Figure 3 is a schematic diagram of the in-group balancing topology structure provided by the embodiment of the present invention;

[0057] Figure 4 is a circuit state diagram when the first conducting element is conducting provided by the embodiment of the present invention;

[0058] Figure 5 is a circuit state diagram when the first conducting element is disconnected provided by the embodiment of the present invention;

[0059] Figure 6 is a schematic diagram of the inter-group balancing topology structure provided by the embodiment of the present invention;

[0060] Figure 7 is a schematic diagram of P1 discharging provided by the embodiment of the present invention;

[0061] Figure 8 is a schematic diagram of P2 being charged provided by the embodiment of the present invention;

[0062] Figure 9 is a schematic diagram of L1 demagnetization provided by the embodiment of the present invention;

[0063] Figure 10 is a schematic diagram of the flow of an energy balancing method provided by the embodiment of the present invention. Detailed implementation mode

[0064] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the description of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0066] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediate element. In the following embodiments, "connection", if there is a transmission of electrical signals or data between the connected circuits, modules, units, etc., should be understood as "electrical connection", "communication connection", etc.

[0067] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprising / including" or "having" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0068] Figure 2 is a schematic structural diagram of an energy storage device provided by an embodiment of the present invention.

[0069] Figure 2 It is shown that the energy storage device includes at least two battery packs, and each battery pack includes at least two single cells;

[0070] At least one in-group balancing circuit configured in each of the battery packs, and the in-group balancing circuit is used to balance the energy between the single cells within the group;

[0071] At least one between-group balancing circuit configured between at least two of the battery packs, and the between-group balancing circuit is used to balance the energy between the battery packs;

[0072] A battery state collector, a controller, and a driving circuit;

[0073] The battery state collector is used to collect the energy states of individual battery cells and each battery pack, and send the energy states of the individual battery cells and each battery pack to the controller;

[0074] The controller is used to receive the energy states of individual battery cells and each battery pack sent by the battery state collector, and send a driving instruction to the driving circuit;

[0075] The driving circuit is used to receive the driving instruction of the controller, and drive the intra-group equalization circuit and the inter-group equalization circuit to work according to the driving instruction.

[0076] It can be understood that, based on the traditional Cuk equalization circuit topology, the embodiment of the present invention proposes a new type of two-stage equalization topology, which groups adjacent individual battery cells to achieve the two-stage equalization function of the battery. As Figure 2 shown, n individual battery cells are divided into m groups, and each group contains p individual battery cells. Each battery pack contains an intra-group equalization sub-circuit, that is, there are m intra-group equalization sub-circuits in total. There are m - 1 inter-group equalization circuits between groups.

[0077] For the intra-group equalization topology of the two-stage equalization topology circuit provided by the embodiment of the present invention, a common Cuk equalizer is used, and the number of inductors and capacitors is reduced by multiples, reducing the hardware requirements and saving costs. By selecting switches, energy transfer between any individual battery cells within the group is achieved, thereby shortening the energy transfer path, indirectly reducing energy loss, and improving the equalization speed. For the inter-group equalization topology, a Buck-Boost circuit topology is adopted, allowing bidirectional energy flow, making the equalization process smoother and the equalization effect better.

[0078] In terms of inter-group equalization, the embodiment of the present invention adopts a Buck-Boost circuit topology, and the common resistor and energy storage inductor between every two adjacent battery packs can achieve energy transfer between adjacent battery packs. The inter-group equalization circuit in which m battery packs are connected in series is composed of 2m - 2 MOSFETs, 2m - 2 diodes, m - 1 resistors and m - 1 energy storage inductors.

[0079] Taking battery packs P1 and P2 as an example, assuming that the average energy of battery pack P1 is higher than that of battery pack P2, then inter-group equalization will be carried out between battery packs P1 and P2.

[0080] The embodiment of the present invention proposes a new type of two-stage equalization topology circuit, which groups adjacent individual battery cells to achieve the two-stage equalization function of the battery, and solves the safety problems and premature failure problems such as capacity and efficiency decline caused by the SOC imbalance of individual battery cells with a faster equalization speed.

[0081] Based on the above embodiments, the in-group balancing circuit is configured with a balancing control circuit, and at least two upper switches and at least two lower switches respectively connected to the single cells;

[0082] The upper switches and the lower switches form a charge-discharge loop with the balancing control circuit;

[0083] The balancing control circuit controls the charge-discharge loop to perform charge and discharge according to the driving instruction.

[0084] The balancing control circuit controls the charge-discharge loop to perform charge and discharge according to the driving instruction, which specifically includes:

[0085] The battery state collector confirms that there is currently a single cell in a high energy state and a single cell in a low energy state. The controller sends a driving instruction to the driving circuit, and the driving circuit drives the balancing control circuit to control the charge-discharge loop to perform charge and discharge according to the driving instruction.

[0086] Meanwhile, the embodiment of the present invention also adds a double-layer circuit switch design on the basis of the Cuk balancing circuit topology. Figure 3 It is a schematic diagram of the in-group balancing topology structure provided by the embodiment of the present invention. As Figure 3 shown, assuming there are n series-connected single cells in the group, then each single cell corresponds to an upper switch and a lower switch. There are a total of n upper switches (S1a, S2a, S3a,..., Sia,..., Sna), and a total of n lower switches (S1b, S2b, S3b,..., Sib,..., Snb). The energy transfer between the unbalanced single cells in the group is completed through the Cuk balancing circuit, that is, the balancing control circuit in the embodiment of the present invention.

[0087] It can be understood that the double-layer selection switches in the embodiment of the present invention share a Cuk balancing circuit. Although the total number of switches increases, the number of inductors and capacitors is reduced by a factor of two, reducing the hardware requirements and saving costs. When the number of single cells increases, only the number of selection switches needs to be increased, and the circuit complexity remains unchanged.

[0088] Based on the above embodiments, the balancing control circuit is configured as a Cuk circuit, and the Cuk circuit includes:

[0089] A first inductor and a first conducting element;

[0090] The first inductor, the first conducting element and the single cell in the high energy state form a first loop;

[0091] A second inductor and a first capacitor;

[0092] The second inductor, the first capacitor and the low-energy-state single battery form a second loop;

[0093] The first loop and the second loop are externally connected to the drive circuit;

[0094] The first loop is used to control the high-energy-state single battery to discharge and store in the first inductor according to the drive of the drive circuit;

[0095] The second loop is used to control the first capacitor to discharge according to the drive of the drive circuit, and the second inductor charges the low-energy-state single battery.

[0096] The current change during the controller drive control is:

[0097]

[0098]

[0099] Wherein, is the average current passing through the first inductor, is the average current passing through the second inductor, Vc is the capacitor voltage, V B1 and V Bi are the high-energy single battery voltage and the low-energy single battery voltage connected to the Cuk circuit respectively, D is the duty cycle, and Ts is the switching period.

[0100] To ensure that the inductor current is continuous and there is no step change, according to the design standard, the relationship between the currents of inductors L1 and L2 and the average value is:

[0101] i L1 <30%I

[0102] i L2 <30%I

[0103] According to the on and off states of the switching transistor Q1, from the power transfer relationship, it can be obtained that:

[0104]

[0105] V B1 and V Bi are the input voltage and the output voltage of the Cuk balancing circuit respectively, D is the duty cycle, and Ts is the switching period.

[0106] The input-output relationship of the Cuk circuit is:

[0107]

[0108] The average current during the energy transfer process and the capacitor voltage Vc are as follows:

[0109]

[0110] Vc is the amount of electricity obtained when the battery B1, the inductor L1, and the capacitor C1 form a loop during the turn-off period of the switching transistor Q1 and charge the capacitor C1. V B1 and V Bi are respectively the high-energy-side single-cell voltage and the low-energy-side single-cell voltage connected to the Cuk circuit. It can be seen that when the two single-cell voltages participating in the equalization and the Cuk parameters are known, the equalization current is only related to the duty cycle and period of the control signal of Q1.

[0111] Based on the above embodiments, the Cuk circuit further includes:

[0112] A second conducting element;

[0113] The first capacitor, the first inductor, and the high-energy-state single-cell battery form a third loop;

[0114] The second inductor, the second conducting element, and the low-energy-state single-cell battery form a fourth loop;

[0115] The third loop and the fourth loop are externally connected to the drive circuit;

[0116] The third loop is used to control the discharge of the first inductor and the high-energy-state single-cell battery and the charging of the first capacitor according to the drive of the drive circuit;

[0117] The fourth loop is used to control the charging of the second inductor for the low-energy-state single-cell battery according to the drive of the drive circuit.

[0118] Figure 3 is a schematic diagram of the intra-group equalization topology structure provided by the embodiments of the present invention. As Figure 3 shown, the intra-group equalization topology adopts the form of combining the Cuk circuit topology with a double-layer switch. The Cuk equalization circuit includes two inductors (the first inductor L1 and the second inductor L2), a capacitor C1, two diodes (the first diode D1 and the second diode D2), and a switching transistor Q1. Q1 is the first conducting element in the embodiments of the present invention, and is specifically shown as the combination of the switching transistor Q1 and the diode D1 in the figure. The second conducting element is specifically shown as the second diode D2 in the figure. The present invention does not specifically limit other conduction methods in the embodiments.

[0119] In the embodiments of the present invention, refer to Figure 3As shown, the upper - layer switches (S1a, S2a, S3a, …, Sia, …, Sna) control low - energy single - cell batteries, and the lower - layer switches (S1b, S2b, S3b, …, Sib, …, Snb) control high - energy single - cell batteries. That is, after the high - energy single - cell battery discharges, through the Cuk balancing circuit, the electric energy is transmitted to the low - energy battery cell for charging, thereby realizing the transmission of electric energy.

[0120] Based on the above - mentioned embodiment, when the first switching tube is turned on, the first inductor charges and stores energy, and the first capacitor and the second inductor form a first loop, and the energy in the first capacitor is released to the second inductor.

[0121] It can be understood that, referring to Figure 2 、 Figure 3 Taking the energy imbalance between battery B1 and battery Bi as an example, where the energy of battery B1 is higher than that of battery Bi. After the lower - layer switch S1b and the upper - layer switch Sia are closed, within one signal period, due to the on - off of the fully - controlled switching tube Q1, the balancing circuit presents two states.

[0122] Figure 4 is the circuit state diagram when the first conducting element in the embodiment of the present invention is turned on. As Figure 4 shown, when the switching tube Q1 is turned on, as Figure 5 shown, battery B1 and inductor L1 form a first loop to charge inductor L1, and inductor L1 stores energy. Capacitor C1, inductor L2 and battery Bi form a second loop, and the energy in capacitor C1 is released to inductor L2 and battery Bi, and at this time battery Bi is charged.

[0123] Figure 5 is the circuit state diagram when the first conducting element in the embodiment of the present invention is turned off. As Figure 5 shown, the free - wheeling diode D2 conducts forward. The left - hand loop is composed of battery B1, inductor L1 and capacitor C1 to form a third loop, and battery B1 and inductor L1 charge capacitor C1, and at this time C1 stores energy. Inductor L2 forms a fourth loop with battery Bi through the free - wheeling diode D2. Due to the fact that the current of the inductor cannot change suddenly, inductor L2 continues to charge battery Bi.

[0124] Based on the above - mentioned embodiment, the inter - group balancing circuit is configured as a buck - boost circuit, and the buck - boost circuit includes:

[0125] A third conducting element and a third inductor;

[0126] The third conducting element, the third inductor and the high - energy battery pack form a fifth loop;

[0127] The fifth loop is externally connected to the drive circuit;

[0128] The fifth circuit is used to control the high-energy battery pack to discharge and charge the third inductor according to the drive of the drive circuit.

[0129] Based on the above embodiments, the buck-boost circuit further includes:

[0130] A fourth conducting element, and the fourth conducting element, the third inductor and the low-energy battery pack form a sixth circuit;

[0131] The sixth circuit is externally connected to the drive circuit;

[0132] The sixth circuit is used to control the third inductor to discharge and charge the low-energy battery pack according to the drive of the drive circuit.

[0133] In terms of inter-group balancing, the embodiment of the present invention adopts a topology based on the Buck-Boost circuit. Figure 6 It is a schematic diagram of the inter-group balancing topology structure provided by the embodiment of the present invention. As Figure 6 shown, the inter-group balancing topology adopts a topology based on the Buck-Boost circuit, as Figure 6 shown. The common resistor and energy storage inductor between every two adjacent battery packs can realize the energy transfer between adjacent battery packs. The inter-group balancing circuit of m series-connected battery packs is composed of 2m - 2 MOSFETs, 2m - 2 diodes, m - 1 resistors

[0134] and m - 1 energy storage inductors.

[0135] For the method of inter-group balancing, it is actually that the battery pack with higher average energy discharges to the battery pack with lower average energy. Taking battery packs P1 and P2 as an example, assuming that the average energy of battery pack P1 is higher than that of battery pack P2, then the inter-group balancing will be carried out between battery packs P1 and P2. The balancing process is mainly divided into the following three steps: P1 discharges, P2 is charged, and L1 demagnetizes.

[0136] Figure 7 It is a schematic diagram of P1 discharging provided by the embodiment of the present invention. As Figure 7 shown, at the beginning of balancing, switch Q1 is turned on and Q2 is turned off. Battery pack P1 discharges, and Q1 and L1 form a fifth circuit. P1 stores energy in L1. After a period of time, Q1 is turned off, and P1 completes the discharging process. The energy transfer path is as Figure 7 shown. At this stage, the current of L1 rises from 0 to the maximum value.

[0137] The formula is:

[0138]

[0139] VP1 is the terminal voltage of the battery pack P1, Ron is the total internal resistance of the discharge circuit, and t on is the conduction time of Q1.

[0140] Figure 8 is the schematic diagram of P2 being charged provided by the embodiment of the present invention. As Figure 8 shown, the switch Q2 is turned on, Q1 is turned off, Q2 and L1 form a sixth loop, and L1 charges the battery pack P2. The energy transfer path is as Figure 8 shown. At this time, the inductor current iL1 is:

[0141]

[0142] i max is the peak current of the inductor, R off is the total resistance of the loop, V P2 is the terminal voltage of the battery pack P2, t on and t off are the times when the switch Q2 is turned on and off respectively.

[0143] The buck-boost circuit is further configured with:

[0144] A demagnetization circuit, which demagnetizes the third inductor after the battery pack with high average energy completes the discharge process and after the battery pack with low average energy finishes charging.

[0145] It can be understood that when the battery pack P2 is being charged, the energy transfer between the two battery packs is completed. Because the inductor has the property of storing energy, during the balancing process, there are still some inductors that will accumulate energy and magnetic saturation will occur. Therefore, demagnetization is required at the end of charging and discharging. During this process, Figure 9 is the schematic diagram of L1 demagnetization provided by the embodiment of the present invention. As Figure 9 shown, the inductor L1 will consume the remaining energy through R1.

[0146] Secondly, Figure 10 is the schematic diagram of the energy balancing method process provided by the embodiment of the present invention. As Figure 9 shown, it includes:

[0147] 1001. Detect and confirm the high-energy-state single cells and low-energy-state single cells in the battery pack;

[0148] 1002. Based on the intra-pack balancing circuit, control the high-energy-state single cells to discharge and transfer to the low-energy-state single cells;

[0149] 1003. Detect and confirm the average energy between the battery packs, and based on the inter-pack balancing circuit, control the battery pack with high average energy to discharge and transfer to the battery pack with low average energy.

[0150] It is understandable that the embodiments of the present invention actually provide a circuit balancing method based on Figure 2 the circuit diagram shown. The core idea of the method is that, first, in step 1001, the high-energy single-cell batteries and low-energy single-cell batteries in each battery pack are identified. Then, in step 1002, the high-energy single-cell batteries are controlled to discharge, and the low-energy single-cell batteries are charged. After the in-group balancing is completed, finally, in step 1003, the inter-group balancing is performed. The inter-group balancing is actually to balance the energy between the battery packs. Therefore, in the embodiments of the present invention, the average energy between the battery packs is detected and confirmed, and then the battery pack with a higher average energy is controlled to discharge and transmit the energy to the battery pack with a lower average energy to complete the inter-group balancing.

[0151] Based on the in-group balancing circuit in the above embodiment, controlling the high-energy single-cell battery to discharge and transmit the energy to the low-energy single-cell battery specifically includes:

[0152] Within one signal cycle, when the first switch tube is turned on, the high-energy single-cell battery and the first inductor form a loop and charge the first inductor;

[0153] The first capacitor, the second inductor and the low-energy single-cell battery form a closed loop, and the energy in the first capacitor is released to the second inductor and the low-energy single-cell battery to charge the low-energy single-cell battery;

[0154] When the first switch tube is turned off, the second diode conducts forward, and the high-energy single-cell battery, the first inductor and the first capacitor form a loop, and the high-energy single-cell battery and the first inductor charge the first capacitor;

[0155] The second inductor forms a closed loop with the low-energy single-cell battery through the second diode, and the second inductor continues to charge the low-energy single-cell battery.

[0156] Detecting and confirming the average energy between the battery packs, and based on the inter-group balancing circuit, controlling the battery pack with a higher average energy to discharge and transmit the energy to the battery pack with a lower average energy specifically includes:

[0157] Turn on the first switch and turn off the second switch. The battery pack with a higher average energy discharges, and a loop is formed between the first switch and the first inductor. The battery pack with a higher average energy stores the energy in the first inductor;

[0158] When the first switch is turned off, the battery pack with a higher average energy completes the discharging process;

[0159] Turn on the second switch and turn off the first switch. A loop is formed between the second switch and the first inductor, and the first inductor charges the battery pack with a lower average energy.

[0160] For the method of inter-group balancing, the battery pack with higher average energy actually discharges to the battery pack with lower average energy. Taking battery packs P1 and P2 as an example, assuming that the average energy of battery pack P1 is higher than that of battery pack P2, then the inter-group balancing will be carried out between battery packs P1 and P2. The balancing process is mainly divided into the following three steps: P1 discharges, P2 is charged, and L1 is demagnetized.

[0161] The main process of inter-group balancing can be referred to the above embodiments, and the embodiments of the present invention will not be elaborated herein.

[0162] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An energy storage device, characterized in that, Comprising: At least two battery packs, each battery pack including at least two single cells; At least one in-group balancing circuit configured in at least one of the battery packs, the in-group balancing circuit being used to balance the energy among the single cells within the group; At least one between-group balancing circuit configured between at least two of the battery packs, the between-group balancing circuit being used to balance the energy among the battery packs; A battery state collector, a controller, and a driving circuit; The battery state collector is used to collect the energy states of the single cells and the energy states of the battery packs, and send the energy states of the single cells and the energy states of the battery packs to the controller; The controller is used to receive the energy states of the single cells and the energy states of the battery packs sent by the battery state collector, and send a driving instruction to the driving circuit; The driving circuit is used to receive the driving instruction of the controller, and drive the in-group balancing circuit and the between-group balancing circuit to work according to the driving instruction.

2. The energy storage device according to claim 1, wherein The in-group balancing circuit is configured with a balancing control circuit, at least two upper switches and at least two lower switches correspondingly connected to the single cells; The upper switches and the lower switches form a charge-discharge loop with the balancing control circuit; The balancing control circuit controls the charge-discharge loop to perform charge and discharge according to the driving instruction.

3. The energy storage device according to claim 2, wherein, The balancing control circuit controls the charge-discharge loop to perform charge and discharge according to the driving instruction, specifically including: The battery state collector confirms that there is currently a single cell in a high energy state and a single cell in a low energy state. The controller sends a driving instruction to the driving circuit, and the driving circuit drives the balancing control circuit to control the charge-discharge loop to perform charge and discharge according to the driving instruction.

4. The energy storage device according to claim 3, characterized in that, The balancing control circuit includes: A first inductor and a first conducting element; The first inductor, the first conducting element and the single cell in the high energy state form a first loop; A second inductor and a first capacitor; The second inductor, the first capacitor and the single cell in the low energy state form a second loop; The first loop and the second loop are externally connected to the driving circuit; The first loop is used to control the single cell in the high energy state to discharge and store in the first inductor according to the driving of the driving circuit; The second loop is used to control the first capacitor to discharge according to the driving of the driving circuit, and the second inductor charges the single cell in the low energy state.

5. The energy storage device according to claim 4, characterized in that, The current change during the controller's driving control is: Among them, is the average current through the first inductor, is the average current through the second inductor, Vc is the capacitor voltage, V B1 and V Bi are respectively the high-energy-state single-cell voltage and the high-energy-state single-cell voltage of the single cell connected to the Chuke circuit, D is the duty cycle, and Ts is the switching period.

6. The energy storage device according to claim 4, characterized in that, The balancing control circuit further includes: A second conducting element; The first capacitor, the first inductor and the single cell in the high energy state form a third loop; The second inductor, the second conducting element and the single cell in the low energy state form a fourth loop; The third loop and the fourth loop are externally connected to the driving circuit; The third loop is used to control the first inductor and the single cell in the high energy state to discharge and the first capacitor to charge according to the driving of the driving circuit; The fourth loop is used to control the second inductor to charge the single cell in the low energy state according to the driving of the driving circuit.

7. The energy storage device according to claim 1, characterized in that The inter-group balancing circuit is configured as a buck-boost circuit, and the buck-boost circuit includes: A third conducting element and a third inductor; The third conducting element, the third inductor and the high-energy battery pack form a fifth loop; The fifth loop is externally connected to the drive circuit; The fifth loop is used to control the discharge of the high-energy battery pack and the charging of the third inductor according to the drive of the drive circuit.

8. The energy storage device according to claim 7, wherein, The buck-boost circuit further includes: A fourth conducting element, and the fourth conducting element, the third inductor and the low-energy battery pack form a sixth loop; The sixth loop is externally connected to the drive circuit; The sixth loop is used to control the discharge of the third inductor and the charging of the low-energy battery pack according to the drive of the drive circuit.

9. The energy storage device according to claim 8, wherein, The buck-boost circuit is further configured with: A demagnetization circuit, which demagnetizes the third inductor after the battery pack with high average energy completes the discharge process and after the battery pack with low average energy finishes charging.

10. An energy balancing method implemented based on the energy storage device according to any one of claims 1-9, characterized in that, Including: Detecting and confirming the high-energy state single cells and low-energy state single cells in the battery pack; Based on the intra-group balancing circuit, controlling the high-energy state single cells to discharge and transfer to the low-energy state single cells; Detecting and confirming the average energy between battery packs, and based on the inter-group balancing circuit, controlling the battery pack with high average energy to discharge and transfer to the battery pack with low average energy.

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