High-side single-tube stack active equalization circuit, circuit control method and energy storage system

Abstract

This application relates to a high-side single-transistor stacked active balancing circuit, a circuit control method, and an energy storage system. The high-side single-transistor stacked active balancing circuit includes an input inductor, a high-side switch, and M stacked balancing units. The high-side switch is used to be in a conducting state when the current in each branch of the circuit is zero for a duration reaching a time threshold, so that the input inductor and each stacked balancing unit are in a charging state. When the high-side switch is off, the input inductor and each stacked balancing unit are in a discharging state, so as to charge the cell with the lowest single-cell voltage among the M cells, or one or all M cells. The circuit control method is used to control the high-side single-transistor stacked active balancing circuit. The energy storage system includes the high-side single-transistor stacked active balancing circuit.

Description

Technical Field

[0001] This application relates to the field of active battery balancing technology, and in particular to a high-side single-tube stacked active balancing circuit, circuit control method and energy storage system. Background Technology

[0002] With the rapid development of energy storage systems, using multiple individual battery cells connected in series to form a medium-to-high voltage DC bus has become a common technical approach for energy storage systems. Although connecting individual battery cells in series can meet the voltage level requirements of the energy storage system, the unavoidable variations in capacity, internal resistance, self-discharge rate, temperature distribution, and aging degree of each battery cell will cause the voltage of each cell to gradually deviate after a period of operation, resulting in a voltage imbalance problem.

[0003] Voltage balancing technology includes two main categories: active balancing technology and passive balancing technology. Currently, active balancing technology is an important research direction for high-performance energy storage systems. However, current active balancing circuits typically suffer from a large number of components and long conduction paths, which obviously leads to significant energy loss. Summary of the Invention

[0004] Therefore, it is necessary to provide a high-side single-tube stacked active balancing circuit, circuit control method and energy storage system that can reduce energy loss.

[0005] In a first aspect, embodiments of this application provide a high-side single-transistor stacked active equalization circuit, the circuit comprising:

[0006] The input inductor, high-side switching transistor, and M stacked equalization units, where M is an integer greater than 1, and the M stacked equalization units correspond one-to-one with the M batteries in the battery pack.

[0007] The first terminal of the high-side switch is connected to the first terminal of the Mth stacked equalization unit and the first terminal of the Mth battery, respectively; the second terminal of the high-side switch is connected to the second terminal of the input inductor and the third terminal of each stacked equalization unit, respectively.

[0008] The first terminal of the input inductor is connected to the second terminal of the first stacked equalization unit, the second terminal of the first battery, and the ground terminal, respectively.

[0009] Each stacked equalization unit is connected in parallel to the two ends of the corresponding battery through the first end and the second end, and the first end of the Nth stacked equalization unit is connected to the second end of the (N+1)th stacked equalization unit, where N is an integer greater than or equal to 1 and less than or equal to M-1.

[0010] The high-side switch is used to be in the conducting state when the current in each branch of the circuit is 0 for a time threshold, so that the input inductor and each stacked equalization unit are in the charging state.

[0011] When the high-side switch is turned off, the input inductor and each stacked equalization unit are in a discharging state to charge the cell with the lowest single-cell voltage among the M cells or the M cells.

[0012] In one exemplary embodiment, the circuit further includes an input capacitor;

[0013] The first terminal of the input capacitor is connected to the first terminal of the high-side switch, the first terminal of the Mth stacked equalization unit, and the first terminal of the Mth battery, respectively. The second terminal of the input capacitor is connected to the first terminal of the input inductor, the second terminal of the first stacked equalization unit, the second terminal of the first battery, and the ground terminal, respectively.

[0014] In one exemplary embodiment, the stacked equalization unit includes stacked capacitors, stacked inductors, and stacked diodes;

[0015] The first end of the stacked inductor is the first end of the stacked equalization unit, and the second end of the stacked inductor is connected to the first end of the stacked capacitor and the negative terminal of the stacked diode, respectively.

[0016] The positive terminal of the stacked diode is the second end of the stacked equalization unit;

[0017] The second end of the stacked capacitor is the third end of the stacked equalization unit.

[0018] In one exemplary embodiment, the withstand voltage rating of the high-side switch is positively correlated with M and the rated voltage of the individual cells of the battery, respectively.

[0019] The current rating of the high-side switching transistor is positively correlated with the target equalization current of the circuit.

[0020] In one exemplary embodiment, the high-side switch is a MOSFET or an IGBT.

[0021] In a second aspect, embodiments of this application provide a circuit control method for controlling a circuit as described in any of the first aspects of this application, the circuit control method comprising:

[0022] Get the voltage of M batteries;

[0023] Based on the voltages of M batteries, determine the maximum voltage difference; the maximum voltage difference is the difference between the highest and lowest voltages of the M batteries.

[0024] When the maximum voltage difference is greater than the voltage threshold, the high-side switch is turned on; or when the maximum voltage difference is less than or equal to the voltage threshold, the high-side switch is turned off.

[0025] In an exemplary embodiment, controlling the high-side switch to turn on when the maximum voltage difference is greater than a voltage threshold includes:

[0026] When the maximum voltage difference is greater than the voltage threshold, the high-side switch is turned on. During the turn-on process of the high-side switch, the target duty cycle of the control signal is determined based on the maximum voltage difference. The high-side switch is driven based on the control signal with the target duty cycle so that the circuit current can drop to 0 after the high-side switch is turned off.

[0027] In one exemplary embodiment, obtaining the voltage of the multiple batteries includes:

[0028] Obtain the voltage and temperature of multiple batteries;

[0029] When the maximum voltage difference exceeds the voltage threshold, the high-side switch is controlled to turn on, including:

[0030] When the maximum voltage difference is greater than the voltage threshold, the high-side switch is turned on. During the turn-on process of the high-side switch, the target duty cycle of the control signal is determined based on the maximum voltage difference and the temperature of multiple batteries.

[0031] In one exemplary embodiment, the inductance value of the input inductor, the inductance value of the stacked inductors in each stacked equalization unit, and the target duty cycle are such that the current in the circuit can drop to 0 after the high-side switch is turned off.

[0032] Thirdly, embodiments of this application provide an energy storage system, the system comprising a circuit as described in any one of the first aspects of this application, M batteries, a data acquisition module, and a controller, wherein the controller is connected to the data acquisition module;

[0033] The data acquisition module is used to acquire the voltage of M batteries;

[0034] A controller for performing the method as described in any of the second aspects of this application.

[0035] The aforementioned high-side single-tube stacked active balancing circuit, circuit control method, and energy storage system, since the high-side single-tube stacked active balancing circuit includes an input inductor, a high-side switch, and M stacked balancing units, the high-side switch is used to be in a conducting state when the current in each branch of the circuit is zero for a duration reaching a time threshold, so that the input inductor and each stacked balancing unit are in a charging state; when the high-side switch is off, the input inductor and each stacked balancing unit are in a discharging state, so as to charge the one or M batteries with the smallest single-cell voltage among the M batteries. The circuit provided in this embodiment only includes an input inductor, a high-side switch, and M stacked balancing units arranged in a stacked manner. Therefore, the circuit uses fewer components and has a shorter conduction path, which can significantly reduce energy loss. At the same time, the circuit has a clear hierarchical expansion relationship, thus facilitating the expansion of the number of series-connected batteries and providing greater flexibility in use. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A schematic diagram of a high-side single-tube stacked active equalization circuit provided in an embodiment of this application;

[0038] Figure 2 A schematic diagram of another high-side single-tube stacked active equalization circuit provided in this application embodiment;

[0039] Figure 3 A schematic diagram of another high-side single-tube stacked active equalization circuit provided in this application embodiment;

[0040] Figure 4 A schematic flowchart of a circuit control method provided in an embodiment of this application;

[0041] Figure 5 This is a flowchart illustrating another circuit control method provided in an embodiment of this application. Detailed Implementation

[0042] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0044] It is understood that the terms "first," "second," etc., used herein may be used to describe different ends of various components, but these different ends of the components are not limited by these terms. These terms are only used to distinguish one end of a component from the other end of the component. For example, without departing from the scope of this application, the first end of an input inductor may be referred to as the second end of an input inductor, and similarly, the second end of an input inductor may be referred to as the first end of an input inductor. Both the first end and the second end of an input inductor are ends of the input inductor, but they are not the same end of the input inductor.

[0045] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0046] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0047] When used herein, the singular forms of “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 preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0048] The following diagram illustrates the concept using M=4 as an example. Figure 1 As shown, one embodiment of the high-side single-transistor stacked active equalization circuit 100 includes:

[0049] The input inductor Lin, the high-side switch Q, and M stacked equalization units 102 (102-1 / 102-2 / 102-3 / 102-4), where M is an integer greater than 1, and the M stacked equalization units 102 correspond one-to-one with the M batteries (B1 / B2 / B3 / B4) in the battery pack.

[0050] The first terminal of the high-side switch Q is connected to the first terminal of the Mth stacked equalization unit 102 and the first terminal of the Mth battery, respectively. The second terminal of the high-side switch Q is connected to the second terminal of the input inductor Lin and the third terminal of each stacked equalization unit 102, respectively.

[0051] The first terminal of the input inductor Lin is connected to the second terminal of the first stacked equalization unit 102, the second terminal of the first battery, and the ground terminal, respectively.

[0052] Each stacked equalization unit 102 is connected in parallel to the two ends of the corresponding battery through the first end and the second end, and the first end of the Nth stacked equalization unit 102 is connected to the second end of the (N+1)th stacked equalization unit 102, where N is an integer greater than or equal to 1 and less than or equal to M-1.

[0053] The high-side switch Q is used to be in the conducting state when the duration of the current in each branch of the circuit is 0 reaches the time threshold, so that the input inductor Lin and each stacked equalization unit 102 are in the charging state respectively.

[0054] When the high-side switch Q is turned off, the input inductor Lin and each stacked equalization unit 102 are in a discharging state to charge the cell with the smallest single-cell voltage among the M cells or the M cells.

[0055] The input inductor Lin serves as one of the main energy storage devices in the circuit. When the high-side switch Q is on, the input inductor Lin stores energy; when the high-side switch Q is off, the input inductor Lin releases energy.

[0056] The high-side switch Q is the only active control device in the circuit; that is, the stacked equalization unit 102 does not include any active control devices. Since neither of the two ends of the high-side switch Q is connected to ground, the location of the high-side switch Q has a certain potential. That is, the high-side switch Q is set in the high-potential branch on the input side of the circuit, hence it is called a "high-side" switch.

[0057] In an exemplary embodiment, the high-side switch Q is a MOSFET or an IGBT.

[0058] Among them, MOSFET stands for Metal-Oxide-Semiconductor Field-Effect Transistor; IGBT stands for Insulated Gate Bipolar Transistor.

[0059] Optionally, if the high-side switch Q is a MOSFET, the high-side switch Q can be a SiC MOSFET; alternatively, the high-side switch Q can also be a GaN power device.

[0060] Optionally, the high-side switch Q also includes a control terminal, which is connected to the controller. Based on this, the high-side switch Q switches between the on and off states in response to the control signal from the controller.

[0061] Each of the M stacked equalization units 102 can be used to undertake the role of energy storage and energy transfer at each level, and can also establish coupling relationships between levels and node potential conversion relationships. It can also limit the current flow direction to ensure that the equalization energy can flow in the expected direction.

[0062] M batteries are arranged in series. Each of the M stacking equalization units 102 is arranged sequentially along the battery pack hierarchy. Based on the high-side switch Q, the input inductor Lin, and the hierarchical coordination of the M stacking equalization units 102, the circuit provided in this embodiment forms an energy redistribution network for multiple series-connected batteries.

[0063] The first end of the Nth stack equalization unit 102 is connected to the second end of the (N+1)th stack equalization unit 102. That is, the first end of the first stack equalization unit 102-1 is connected to the second end of the second stack equalization unit 102-2, the first end of the second stack equalization unit 102-2 is connected to the second end of the third stack equalization unit 102-3, the first end of the third stack equalization unit 102-3 is connected to the second end of the fourth stack equalization unit 102-4, and so on.

[0064] Optionally, the battery can be a lithium-ion battery, a lithium iron phosphate battery, a sodium-ion battery, or a supercapacitor. Based on this, the circuit provided in this embodiment has a wide range of applications.

[0065] Of the M batteries, the second end of the first battery and the first segment of the Mth battery together form the input bus.

[0066] Optionally, the circuit provided in this embodiment can operate in discontinuous conduction mode. In discontinuous conduction mode, one switching cycle of the circuit provided in this embodiment can be divided into three stages. The three stages include a sequentially occurring conduction stage, a freewheeling discharge stage, and a zero-current stage. That is, in one switching cycle, the circuit first enters the conduction stage, then the freewheeling discharge stage, and finally the zero-current stage.

[0067] In order for the circuit provided in this embodiment to operate in discontinuous conduction mode, in one switching cycle, the circuit provided in this embodiment should have a stage in which the current of the input inductor Lin and the current of the M stacked equalization units 102 are both 0.

[0068] When the circuit provided in this embodiment operates in discontinuous conduction mode, on the one hand, the branch current can drop back to 0 at the end of each switching cycle to avoid the adverse situation of continuous commutation in the circuit; on the other hand, when the voltage of each individual battery is inconsistent, the energy storage and dissipation of each branch will show a difference from the voltage of the individual battery, which is conducive to forming a natural balance mechanism under simplified control.

[0069] In the first stage of a switching cycle, namely the conduction stage, the high-side switch Q is turned on. The input power supply forms an energy storage circuit through the input inductor Lin and the branch containing the M stacked equalization units 102. At this time, the current in the input inductor Lin and the branch containing the M stacked equalization units 102 begins to rise, and the input inductor Lin and the M stacked equalization units 102 establish magnetic field energy. For single cells with higher terminal voltage, their corresponding branches are more likely to form a larger current slope and a higher peak current within the same conduction time. Therefore, single cells with higher terminal voltage will release more energy in the subsequent stages.

[0070] In the second phase of a switching cycle, namely the freewheeling discharge phase, the high-side switch Q switches from the on state to the off state, and the energy stored in the input inductor Lin and the M stacked equalization units 102 begins to be released. In this phase, the energy stored in each stacked equalization unit 102 is guided to the higher-level nodes, the common stacking channel, or the individual cell side with a relative voltage, thereby enabling the energy redistribution from the high-voltage individual cell to the low-voltage individual cell.

[0071] After the current in each branch drops to zero during the freewheeling discharge phase, the circuit provided in this embodiment enters the third stage of a switching cycle, namely the zero-current stage. In this stage, the current in the branch containing the input inductor Lin and the M stacked equalization units 102 is essentially zero, and the equalization network composed of the input inductor Lin and the M stacked equalization units 102 is waiting for the next switching cycle to arrive. The existence of the zero-current stage is an important characteristic of the intermittent conduction mode and a crucial foundation for the circuit provided in this embodiment to achieve active equalization under relatively simplified control conditions.

[0072] Optionally, the existence of a zero-current phase can be ensured by reasonably selecting the switching frequency of the high-side switch Q, the duty cycle of the control signal used to control the on / off state of the high-side switch Q, and the parameters of the input inductor Lin, so that the circuit provided in this embodiment can operate in discontinuous conduction mode.

[0073] In this embodiment, when the battery pack consisting of M batteries is in a voltage balanced state, the average energy distribution of the hierarchical branches of each stacking equalization unit 102 tends to be consistent within one switching cycle. Therefore, the terminal voltage of each battery cell can be maintained at a similar level. When the M batteries are in a voltage unbalanced state, the branches corresponding to high-voltage cells tend to accumulate more energy during the conduction phase and release energy to other cells or the common channel during the freewheeling discharge phase, while low-voltage cells are relatively able to receive more energy. After multiple switching cycles, the voltage difference between the cells gradually decreases, eventually achieving energy balance among the M batteries.

[0074] Based on this, it can be seen that the circuit provided in this embodiment does not rely on configuring a complex energy selection switch for each individual battery cell. Instead, it utilizes the stacked structure composed of M stacked equalization units 102 and the working mechanism of the intermittent conduction mode to achieve adaptive energy redistribution at the topology level.

[0075] After charging either the cell with the lowest voltage among M cells or all M cells, the maximum voltage difference between the highest and lowest voltage cells among the M cells is less than or equal to a voltage threshold.

[0076] Alternatively, in addition to such Figure 1 In addition to the four-cell series structure shown, the circuit provided in this embodiment can also be applied to battery packs with more cells. That is, M can be any number other than 4. This application does not limit the number of cells or the number of stacking equalization units 102. When it is necessary to increase the size of M, that is, to connect more cells in series, it is only necessary to continue to add stacking equalization units 102 corresponding to the newly connected cells according to the cell hierarchy. The same applies when the number of cells needs to be reduced. That is to say, the circuit provided in this embodiment based on the stacking structure can be applied to scenarios where the number of cells is modified. It can be seen that, compared with the traditional battery equalization circuit that requires multiple winding transformers or a large number of switching transistors, the circuit provided in this embodiment does not need to proportionally increase the number of high-side switching transistors Q when the structure is expanded. No matter how large the number of M cells or M stacking equalization units 102 are, the circuit provided in this embodiment only needs to use one high-side switching transistor Q. Therefore, the circuit provided in this embodiment has a good cell expansion capability and can be applied to large-scale series-connected battery packs.

[0077] The aforementioned high-side single-transistor stacked active balancing circuit 100 includes an input inductor Lin, a high-side switch Q, and M stacked balancing units 102. The high-side switch Q is turned on when the current in each branch of the circuit is zero for a duration reaching a time threshold, so that the input inductor Lin and each stacked balancing unit 102 are in a charging state. When the high-side switch Q is turned off, the input inductor Lin and each stacked balancing unit 102 are in a discharging state, so as to charge the one or M batteries with the smallest single-cell voltage among the M batteries. The circuit provided in this embodiment only includes an input inductor Lin, a high-side switch Q, and M stacked balancing units 102 arranged in a stacked manner. Therefore, the circuit uses fewer components and has a shorter conduction path, which can significantly reduce energy loss. At the same time, the circuit has a clear hierarchical expansion relationship, thus facilitating the expansion of the number of series-connected batteries and providing greater flexibility in use.

[0078] In one exemplary embodiment, such as Figure 2 As shown, the circuit also includes an input capacitor Cin;

[0079] The first terminal of the input capacitor Cin is connected to the first terminal of the high-side switch Q, the first terminal of the Mth stacked equalization unit 102, and the first terminal of the Mth battery, respectively. The second terminal of the input capacitor Cin is connected to the first terminal of the input inductor Lin, the second terminal of the first stacked equalization unit 102, the second terminal of the first battery, and the ground terminal, respectively.

[0080] The input capacitor Cin is connected across the input bus to stabilize the input voltage and absorb the pulsating energy generated by the high-side switch Q during switching. Therefore, including the input inductor Lin in the circuit further reduces energy loss.

[0081] In one exemplary embodiment, such as Figure 3 As shown, the stacked equalization unit 102 includes stacked capacitors (C1 / C2 / C3 / C4), stacked inductors (L1 / L2 / L3 / L4), and stacked diodes (D1 / D2 / D3 / D4).

[0082] The first end of the stacked inductor is the first end of the stacked equalization unit 102, and the second end of the stacked inductor is connected to the first end of the stacked capacitor and the negative terminal of the stacked diode, respectively.

[0083] The positive terminal of the stacked diode is the second end of the stacked equalization unit 102;

[0084] The second end of the stacked capacitor is the third end of the stacked equalization unit 102.

[0085] Among them, stacked capacitors are used to undertake the functions of energy storage and energy transfer in stages.

[0086] Stacked inductors are used to establish coupling relationships between layers and node potential transition relationships.

[0087] Stacked diodes are used to limit the direction of current flow to ensure that balanced energy flows in the desired direction.

[0088] Since the M stacked equalization units 102 have M stacked inductors, the circuit provided in this embodiment realizes the energy storage characteristics of the input inductor Lin and the M stacked inductors, so that different level branches can complete the unified energy storage and layered energy release actions within the same switching cycle.

[0089] In the first stage of a switching cycle, the conduction stage, the high-side switch Q turns on. The input power supply forms an energy storage circuit through the input inductor Lin and the branches containing the stacked equalization units 102. At this time, the current in the input inductor Lin and the branches containing the M stacked inductors begins to rise, and the energy storage elements, including the input inductor Lin and the M stacked inductors, establish magnetic field energy. Due to the polarity and node potential relationship of the stacked diodes, the M stacked diodes are either in the off state or do not play a major role in energy transfer during this conduction stage. Therefore, the energy in the conduction stage mainly accumulates in the input inductor Lin and the M stacked inductors. For single cells with higher terminal voltages, their corresponding branches are more likely to form a larger current slope and a higher peak current within the same conduction time. Therefore, single cells with higher terminal voltages will release more energy subsequently.

[0090] In the second phase of a switching cycle, the freewheeling energy release phase, the high-side switch Q switches from the on state to the off state, and the energy stored in the input inductor Lin and the M stacked inductors begins to be released through their respective diodes. In this phase, the M diodes become the main freewheeling and energy transfer channels. The energy stored in each stacked inductor is guided to higher-level nodes, common stacking channels, or the individual cell side at a relative voltage, thereby enabling energy redistribution from high-voltage to low-voltage cells. Since diodes only allow unidirectional conduction, energy backflow into unwanted branches is prevented, ensuring that balanced energy flows in the predetermined direction.

[0091] After the current in each branch drops to zero during the freewheeling discharge phase, the circuit provided in this embodiment enters the third stage of a switching cycle, namely the zero-current stage. In this stage, the current in the input inductor Lin and the branches containing the M stacked inductors is essentially zero, the M diodes are turned off, and the balancing network composed of the input inductor Lin and the M stacked balancing units 102 is waiting for the next switching cycle to arrive. The existence of the zero-current stage is an important characteristic of the discontinuous conduction mode and a crucial foundation for the circuit provided in this embodiment to achieve active balancing under relatively simplified control conditions.

[0092] Alternatively, the input inductor Lin and each stacked inductor can be a discrete inductor, a coupled inductor, or an integrated magnetic component.

[0093] Alternatively, fast recovery diodes or Schottky diodes can be used for stacking diodes. Of course, synchronous rectifiers can also be used instead of stacked diodes if it is necessary to further improve the battery energy balancing efficiency.

[0094] Optionally, the capacitance value of the stacked capacitors can be designed based on the rated single-cell voltage of the battery, the target equalization power or target equalization current of the circuit, and the allowable current ripple of the circuit.

[0095] The circuit provided in this embodiment does not rely on a single fixed component value in terms of parameter design, but follows the following principles: the inductance value of the input inductor Lin and the inductance values ​​of each stacked inductor should ensure that the circuit can operate in discontinuous conduction mode while guaranteeing the target balanced power or target balanced current and the switching frequency of the high-side switch Q; the capacitance value of each stacked inductor should meet the requirements of node coupling and voltage support, and should keep the voltage ripple of the stacked capacitor within a preset ripple range; the capacitance value of the input capacitor Cin should be able to stabilize the voltage of the input bus and suppress the pulsation phenomenon caused by the high-side switch Q switching between the on and off states.

[0096] In this embodiment, based on the circuit connection relationship, the input inductor Lin is located in the main energy storage channel on the input side. The first segment of the stacked capacitor in each layer of the stacked equalization unit 102 is connected to the common stacking node, and the other end of the stacked capacitor in each layer of the stacked equalization unit 102 is connected to the stacked inductor branch of the corresponding layer. The stacked inductor in each layer of the stacked equalization unit 102 is connected to the corresponding battery level node and connected to the next level node or the common energy transfer path through the corresponding stacked diode. The high-side switch Q is set in the high-potential branch on the input side. When the high-side switch Q is turned on, the entire stacked network composed of M stacked equalization units 102 can complete the energy storage and release process. It can be seen that the advantage of the circuit arrangement provided in this embodiment is that, compared with the traditional low-side switch scheme or multi-switch scheme, the circuit provided in this embodiment not only only needs to use one active device, the high-side switch Q, but also can further optimize the conduction path distribution, reduce the number of diodes used, and significantly reduce energy loss when using fewer devices and shorter conduction paths by increasing the number of inductors used.

[0097] Based on the components and connections of the circuit provided in this embodiment, it can be seen that, compared with traditional battery balancing circuits, firstly, the circuit provided in this embodiment only requires a single high-side switch Q to drive a stacked balancing network composed of M stacked balancing units 102, resulting in fewer switching devices and a simpler control structure; secondly, the circuit provided in this embodiment uses the input inductor Lin and M stacked inductors as the main energy storage devices, which can reduce the dependence on multi-stage diode energy transfer paths in some traditional topologies, thereby reducing conduction losses; thirdly, the circuit provided in this embodiment uses a high-side arrangement for the high-side switch Q, which is beneficial for reorganizing the energy release paths of each layer of stacked balancing units 102, making it easier to demonstrate the structural advantages of "fewer diodes and shorter conduction paths" when transferring energy in multiple layers; furthermore, when the circuit provided in this embodiment operates in discontinuous conduction mode, the branch corresponding to the high-voltage individual battery is more likely to generate a larger peak current, thereby releasing more energy when the high-side switch Q is turned off. Therefore, the circuit provided in this embodiment also has a certain adaptive balancing effect.

[0098] In one exemplary embodiment, the withstand voltage rating of the high-side switch Q is positively correlated with M and the rated voltage of the individual cells of the battery, respectively.

[0099] The current rating of the high-side switch Q is positively correlated with the target equalization current of the circuit.

[0100] The withstand voltage rating of the high-side switch Q refers to the maximum voltage that the drain and source of the high-side switch Q can withstand when it is in the off state.

[0101] The current rating of the high-side switch Q refers to the maximum current that is allowed to continuously flow between the drain and source of the high-side switch Q when it is in the on-state.

[0102] The target equalization current of a circuit refers to the average current that the user expects to transfer from one single cell to other cells during the freewheeling discharge stage.

[0103] In this embodiment, based on the circuit connection relationship, the withstand voltage level of the high-side switch Q can be determined by the size of M and the rated voltage of the individual battery cell. Furthermore, the current level of the high-side switch Q can be determined by the target equalization current of the circuit. Based on this, the selection of the high-side switch Q is relatively simple.

[0104] In one exemplary embodiment, a circuit control method is also provided for controlling a circuit as described in any of the above embodiments of the high-side single-transistor stacked active equalization circuit, such as... Figure 4 As shown, the circuit control method includes steps 402 to 406:

[0105] Step 402: Obtain the voltage of M batteries;

[0106] Step 404: Based on the voltages of the M batteries, determine the maximum voltage difference; the maximum voltage difference is the difference between the highest and lowest voltages of the M batteries.

[0107] Step 406: When the maximum voltage difference is greater than the voltage threshold, control the high-side switch to turn on; or, when the maximum voltage difference is less than or equal to the voltage threshold, control the high-side switch to turn off.

[0108] Specifically, when the maximum voltage difference is less than or equal to the voltage threshold, it indicates that the voltage difference between any two batteries in the M batteries is less than or equal to the voltage threshold.

[0109] Optionally, when the method provided in this embodiment is applied to a controller, the controller can generate a control signal to control the high-side switch to turn on or off.

[0110] Alternatively, the controller may be an MCU (Microcontroller Unit).

[0111] Optionally, the voltage threshold can be determined by the rated voltage of a single cell of the battery, and there can be a positive correlation between the voltage threshold and the rated voltage of a single cell of the battery.

[0112] In this embodiment, during the energy balancing process of M batteries, it is only necessary to control the on / off state of the only active device in the control circuit, namely the only high-side switch. Based on this, compared with the traditional battery balancing circuit that requires independent driving or control of multiple channel batteries, the circuit provided in this embodiment only needs to control the high-side switch, that is, only a single switch, which can significantly improve the engineering implementation convenience of the high-side single-switch stacked active balancing circuit.

[0113] In an exemplary embodiment, controlling the high-side switch to turn on when the maximum voltage difference is greater than a voltage threshold includes:

[0114] When the maximum voltage difference is greater than the voltage threshold, the high-side switch is turned on. During the turn-on process of the high-side switch, the target duty cycle of the control signal is determined based on the maximum voltage difference. The high-side switch is driven based on the control signal with the target duty cycle so that the circuit current can drop to 0 after the high-side switch is turned off.

[0115] This allows the circuit current to drop to 0 after the high-side switch is turned off, meaning that the circuit can operate in an intermittent conduction mode that includes a zero-current phase.

[0116] During the conduction process of the high-side switch, specifically in the intermittent conduction mode and the freewheeling discharge phase, the M batteries undergo energy balancing. Initially, the voltage difference between the high-voltage and low-voltage individual batteries is significant, meaning the maximum voltage difference is large. At this point, the energy storage capacity acting on the input inductor and each stacked inductor is stronger. Since the energy source is primarily the high-voltage individual battery, actively increasing the target duty cycle allows the input inductor and each stacked inductor more energy storage time. Therefore, adjusting the target duty cycle spontaneously prioritizes the adjustment of the high-voltage individual battery. It can be seen that the circuit provided in this embodiment has a certain degree of adaptive balancing effect.

[0117] During the conduction process of the high-side switch, i.e. the conduction phase and freewheeling discharge phase in the intermittent conduction mode, the M batteries are performing energy balancing. During the energy balancing process, the maximum voltage difference gradually decreases. Based on this, in order to maintain the circuit in the intermittent conduction mode and ensure that the circuit can enter the zero-current phase, the high-side switch does not need to have an excessively long conduction time. Therefore, during the conduction process of the high-side switch, as the maximum voltage difference gradually decreases, the controller can actively reduce the target duty cycle based on the maximum voltage difference to ensure that the circuit can enter the zero-current phase.

[0118] Based on this, it can be seen that in one switching cycle of the circuit provided in this embodiment, the target duty cycle is not fixed, but gradually decreases as the maximum voltage difference decreases. Optionally, the target duty cycle can be gradually decreased based on the initial duty cycle, which can be determined based on ensuring the voltage and temperature ratings of each device in the circuit. Since the target duty cycle gradually decreases during the conduction of the high-side switch, it not only enables the circuit to maintain operation in discontinuous conduction mode, but also reduces the stress on each device in the circuit and the energy fluctuation phenomenon between multi-layer nodes.

[0119] In an exemplary embodiment, obtaining the voltages of the M batteries as described above includes:

[0120] Obtain the voltage and temperature of M batteries;

[0121] When the maximum voltage difference exceeds the voltage threshold, the high-side switch is controlled to turn on, including:

[0122] When the maximum voltage difference is greater than the voltage threshold, the high-side switch is turned on. During the turn-on process of the high-side switch, the target duty cycle of the control signal is determined based on the maximum voltage difference and the temperature of the M batteries.

[0123] The voltage and temperature of the M batteries can be acquired in real time, ensuring a balanced and timely response from the batteries.

[0124] The voltages and temperatures of the M batteries can be obtained through a data acquisition module connected to the controller. Optionally, the data acquisition module may include a voltage acquisition unit and a temperature acquisition unit, so that the controller acquires the voltages of the M batteries through the voltage acquisition unit and the temperatures of the M batteries through the temperature acquisition unit.

[0125] With the temperature of the M batteries remaining constant, the maximum voltage difference is positively correlated with the target duty cycle of the control signal.

[0126] When the maximum voltage difference remains constant, there is a negative correlation between the battery temperature and the target duty cycle of the control signal.

[0127] In one exemplary embodiment, the method further includes:

[0128] If an abnormal state is detected, the high-side switch is turned off.

[0129] Abnormal states include at least one of the following states:

[0130] The temperature characteristics of M batteries indicate that at least one battery has a temperature greater than or equal to a temperature threshold.

[0131] The voltage of the M batteries indicates that the voltage of the input bus is within the abnormal voltage range.

[0132] The voltage characteristics of each of the M batteries indicate that the voltage of at least one battery is within the abnormal voltage range.

[0133] In this embodiment, when there is no abnormal state in the circuit, and the maximum voltage difference is less than or equal to the voltage threshold, the high-side switch is turned off. However, when an abnormal state is detected, the high-side switch is turned off regardless of whether the maximum voltage difference is less than or equal to the voltage threshold. Based on this, battery equalization can be terminated in a timely manner when there is an abnormal state in the circuit, so as to ensure the safety of the circuit and the M batteries.

[0134] In one exemplary embodiment, the inductance value of the input inductor, the inductance value of the stacked inductors in each stacked equalization unit, and the target duty cycle are such that the current in the circuit can drop to 0 after the high-side switch is turned off.

[0135] Optionally, the target duty cycle can be determined based on the number of M units and the rated voltage of each individual unit. Since a larger duty cycle of the control signal results in more energy storage in the input inductor and each stacked inductor, it becomes more difficult for the current in the branch of each stacked equalization unit to drop to zero within the switching cycle after the high-side switch is turned off. This makes it more difficult for the circuit to operate in discontinuous conduction mode. Therefore, the target duty cycle is negatively correlated with both the number of M units and the rated voltage of each individual unit.

[0136] Optionally, in addition to the inductance value of the input inductor, the inductance value of the stacked inductors in each stacked equalization unit, and the target duty cycle, the switching frequency of the control signal can also be set so that the circuit current can drop to zero after the high-side switch is turned off. A lower switching frequency of the control signal will result in a larger current ripple and a greater device current stress on the high-side switch; a higher switching frequency of the control signal will result in a shorter actual time for the zero-current phase of the discontinuous conduction mode and will increase the switching losses of the high-side switch. Therefore, the switching frequency of the control signal should not be too high or too low.

[0137] Optionally, the inductance value of the input inductor and the inductance value of the stacked inductors in each stacked equalization unit can be set not only to ensure that the current of the circuit can drop to 0 after the high-side switch is turned off, but also to ensure that the peak current of the circuit is less than the saturation current of the inductor, or to ensure that the equalization current of the circuit is greater than or equal to the equalization current threshold.

[0138] The smaller the inductance values ​​of the input inductor and the stacking inductors of each stacking equalization unit, the faster the current rises in each stacking equalization unit, and the larger the equalization current will be. Based on this, the equalization speed of the M batteries will be faster. However, this will lead to higher current peaks, energy loss, and saturation risk. Conversely, the larger the inductance values ​​of the input inductor and the stacking inductors of each stacking equalization unit, the slower the current rises in each stacking equalization unit, and the smaller the equalization current will be. Based on this, it is easier to control thermal stress, but this will lead to a slower equalization speed of the M batteries. Therefore, the inductance values ​​of the input inductor and the stacking inductors of each stacking equalization unit should not be too small to ensure that the intermittent conduction mode can have a zero-current phase for at least a certain period of time.

[0139] It should be noted that, Figures 1-4 Although the illustrations use M=4 as an example, M=4 is only an optional embodiment in this case. In the actual implementation, M can be any integer greater than 1. This application does not limit the size of M.

[0140] The application process of the above-mentioned circuit control method will be illustrated below with a detailed embodiment, such as... Figure 5 As shown, the details are as follows:

[0141] Step 502: Obtain the voltage of multiple batteries;

[0142] Step 504: Determine the maximum voltage difference based on the voltages of multiple batteries;

[0143] Step 506: Determine whether the maximum voltage difference is greater than the voltage threshold. If the maximum voltage difference is less than or equal to the voltage threshold, proceed to step 508. If the maximum voltage difference is greater than the voltage threshold, proceed to step 510.

[0144] Step 508: If the maximum voltage difference is less than or equal to the voltage threshold, then the voltages of multiple batteries are reacquired.

[0145] Step 510: When the maximum voltage difference is greater than the voltage threshold, control the high-side switch to turn on;

[0146] Step 512: During the conduction process of the high-side switch, the target duty cycle of the control signal is determined based on the maximum voltage difference, and the high-side switch is driven based on the control signal with the target duty cycle.

[0147] Step 514: Determine whether the maximum voltage difference is less than or equal to the voltage threshold. If the maximum voltage difference is greater than the voltage threshold, proceed to step 516. If the maximum voltage difference is less than or equal to the voltage threshold, proceed to step 518.

[0148] Step 516: If the maximum voltage difference is greater than the voltage threshold, the high-side switch is kept on to continue battery energy balancing.

[0149] Step 518: When the maximum voltage difference is less than or equal to the voltage threshold, the high-side switch is turned off. At this point, one switching cycle of the high-side switch ends.

[0150] In one exemplary embodiment, an energy storage system is also provided, the system including a circuit as described in any of the above embodiments of the high-side single-tube stacked active balancing circuit, M batteries, a data acquisition module and a controller, the controller being connected to the data acquisition module;

[0151] The data acquisition module is used to acquire the voltage of M batteries;

[0152] A controller for performing the method as described in any of the above-described embodiments of the circuit control method.

[0153] The data acquisition module can also collect the temperature of M batteries.

[0154] It is understood that the above-mentioned high-side single-tube stacked active equalization circuit can also take other forms, not limited to those mentioned in the above embodiments, as long as it can achieve the function of reducing energy loss.

[0155] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0156] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0157] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A high-side single-transistor stacked active equalization circuit, characterized in that, The circuit includes: The input inductor, high-side switching transistor, and M stacked equalization units, where M is an integer greater than 1, and the M stacked equalization units correspond one-to-one with the M batteries in the battery pack. The first terminal of the high-side switch is connected to the first terminal of the Mth stacked equalization unit and the first terminal of the Mth battery, respectively; the second terminal of the high-side switch is connected to the second terminal of the input inductor and the third terminal of each stacked equalization unit, respectively. The first end of the input inductor is connected to the second end of the first stacked equalization unit, the second end of the first battery, and the ground terminal, respectively. Each of the stacked equalization units is connected in parallel to the two ends of the corresponding battery through a first end and a second end, and the first end of the Nth stacked equalization unit is connected to the second end of the (N+1)th stacked equalization unit, where N is an integer greater than or equal to 1 and less than or equal to M-1. The high-side switch is used to be in the on state when the duration of the maintenance of the current in each branch of the circuit being 0 reaches a time threshold, so that the input inductor and each of the stacked equalization units are in the charging state. When the high-side switch is turned off, the input inductor and each of the stacked equalization units are in a discharging state to charge the cell with the lowest single-cell voltage among the M cells, or the M cells.

2. The circuit according to claim 1, characterized in that, The circuit also includes an input capacitor; The first terminal of the input capacitor is connected to the first terminal of the high-side switch, the first terminal of the Mth stacked equalization unit, and the first terminal of the Mth battery, respectively. The second terminal of the input capacitor is connected to the first terminal of the input inductor, the second terminal of the first stacked equalization unit, the second terminal of the first battery, and the ground terminal, respectively.

3. The circuit according to claim 1, characterized in that, The stacked equalization unit includes stacked capacitors, stacked inductors, and stacked diodes; The first end of the stacked inductor is the first end of the stacked equalization unit, and the second end of the stacked inductor is connected to the first end of the stacked capacitor and the negative terminal of the stacked diode, respectively. The positive terminal of the stacked diode is the second terminal of the stacked equalization unit; The second end of the stacked capacitor is the third end of the stacked equalization unit.

4. The circuit according to claim 3, characterized in that, The withstand voltage rating of the high-side switching transistor is positively correlated with M and the rated voltage of the individual cells of the battery, respectively. The current rating of the high-side switch is positively correlated with the target equalization current of the circuit.

5. The circuit according to claim 1, characterized in that, The high-side switching transistor is a MOSFET or an IGBT.

6. A circuit control method, characterized in that, The circuit control method for controlling the circuit as described in any one of claims 1-5 includes: Obtain the voltage of multiple batteries; Based on the voltages of the multiple batteries, a maximum voltage difference is determined; the maximum voltage difference is the difference between the highest and lowest single-cell voltages among the multiple batteries. When the maximum voltage difference is greater than the voltage threshold, the high-side switch is turned on; or, when the maximum voltage difference is less than or equal to the voltage threshold, the high-side switch is turned off.

7. The method according to claim 6, characterized in that, The step of controlling the high-side switch to turn on when the maximum voltage difference is greater than the voltage threshold includes: When the maximum voltage difference is greater than the voltage threshold, the high-side switch is controlled to turn on. During the turn-on process of the high-side switch, the target duty cycle of the control signal is determined based on the maximum voltage difference. The high-side switch is driven based on the control signal with the target duty cycle so that the current of the circuit can drop to 0 after the high-side switch is turned off.

8. The method according to claim 6, characterized in that, The step of obtaining the voltage of the plurality of batteries includes: Obtain the voltage and temperature of multiple batteries; The step of controlling the high-side switch to turn on when the maximum voltage difference is greater than the voltage threshold includes: When the maximum voltage difference is greater than the voltage threshold, the high-side switch is turned on, and during the turn-on process of the high-side switch, the target duty cycle of the control signal is determined based on the maximum voltage difference and the temperature of the multiple batteries.

9. The method according to claim 7 or 8, characterized in that, The inductance value of the input inductor, the inductance value of the stacked inductors in each of the stacked equalization units, and the target duty cycle are such that the current in the circuit can drop to 0 after the high-side switch is turned off.

10. An energy storage system, characterized in that, The system includes the circuit as described in any one of claims 1-5, M batteries, a data acquisition module, and a controller, wherein the controller is connected to the data acquisition module; The acquisition module is used to acquire the voltage of multiple batteries; The controller is configured to perform the method as described in any one of claims 6-9.

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