Active balancing control circuit and method for power battery pack

Abstract

The present application discloses an active balancing control circuit and method for a power battery pack, the circuit comprising: an energy storage subcircuit, comprising a plurality of battery modules connected in series; a switching subcircuit, connected to the energy storage subcircuit and configured to control at least one battery module to be cut out or connected to the energy storage subcircuit; and a balancing subcircuit, for performing voltage balancing on the remaining battery modules according to the average power before balancing of each battery module in the energy storage subcircuit when the at least one battery module is cut out of the energy storage subcircuit under the control of the switching subcircuit. The active balancing control circuit disclosed in the present application can improve the balancing efficiency and keep the load voltage of the power battery pack relatively stable during balancing.

Description

Technical Field

[0001] The present application relates to the field of battery management technology, and in particular to an active balancing control circuit and method for a power battery pack. Background Art

[0002] The energy of electric vehicles comes from power battery packs, which are usually composed of multiple battery cells connected in series and / or parallel. Affected by the existing battery manufacturing process, there are differences between different battery cells, and factors such as the use environment and cyclic charging and discharging will further aggravate this difference, resulting in reduced energy efficiency of power battery packs and even safety issues. By performing balanced control on the power battery pack, the differences between battery cells can be greatly improved and the service life of the power battery pack can be increased.

[0003] In the related art, active balancing technology usually uses energy storage elements such as inductors and capacitors, and multiple switching elements to transfer energy between battery cells to achieve balancing control. However, the efficiency of this balancing method is usually low, and voltage fluctuations are prone to occur during balancing control. Summary of the invention

[0004] In view of this, the present application provides an active balancing control circuit and method for a power battery pack, which can improve the balancing efficiency and keep the load voltage of the power battery pack relatively stable during the balancing period.

[0005] This application specifically adopts the following technical solutions:

[0006] A first aspect of an embodiment of the present application provides an active balancing control circuit for a power battery pack, the circuit comprising:

[0007] An energy storage subcircuit, comprising a plurality of battery modules connected in series;

[0008] a switching subcircuit, connected to the energy storage subcircuit and configured to control at least one battery module to be switched out of or connected to the energy storage subcircuit;

[0009] The balancing subcircuit is used to balance the voltages of the remaining battery modules according to the average power before balancing of each battery module in the energy storage subcircuit when the at least one battery module is cut out of the energy storage subcircuit under the control of the switching subcircuit.

[0010] Optionally, the switching subcircuit includes a plurality of first switches connected in series;

[0011] Each of the battery modules corresponds to one of the first switches and is connected in parallel with the corresponding first switch.

[0012] Optionally, each of the battery modules includes a battery cell and at least one second switch, and the battery cell is connected in series with the at least one second switch.

[0013] Optionally, the balancing subcircuit includes a third switch, an energy storage module and a compensation module;

[0014] The third switch is connected in series with the energy storage subcircuit;

[0015] The energy storage module is connected in parallel with the series-connected energy storage sub-circuit and the third switch;

[0016] The compensation module is connected in parallel with the third switch and is connected to the switching sub-circuit.

[0017] Optionally, the energy storage module includes a primary winding of a transformer and a fourth switch, and the primary winding and the fourth switch are connected in series;

[0018] The compensation module includes a secondary winding of the transformer and a fifth switch, and the secondary winding and the fifth switch are connected in series.

[0019] Optionally, the coil turns ratio between the primary winding and the secondary winding is n:1, where n is the number of battery modules in the energy storage sub-circuit.

[0020] Optionally, the circuit further includes a power supply circuit, and the power supply circuit is connected in parallel with the energy storage module.

[0021] Another aspect of the embodiment of the present application is to provide an active balancing control method for a power battery pack, which is used in the active balancing control circuit of the power battery pack, and the method includes:

[0022] When it is detected that there is a target battery module in the energy storage subcircuit, the average power of each battery module in the energy storage subcircuit before equalization is obtained, and the target battery module is a battery module with abnormal voltage in the charging mode or the discharging mode;

[0023] Controlling the switching subcircuit to cut the target battery module out of the energy storage subcircuit;

[0024] The balancing subcircuit is controlled to perform voltage balancing on the remaining battery modules according to the average power of each battery module in the energy storage subcircuit before balancing.

[0025] Optionally, controlling the balancing subcircuit to perform voltage balancing on the remaining battery modules according to the average power before balancing of each battery module in the energy storage subcircuit includes:

[0026] Obtaining the remaining power of the target battery module;

[0027] Calculating the balancing time of the balancing subcircuit according to the remaining power of the target battery module and the average power of each battery module before balancing;

[0028] The balancing subcircuit is controlled to perform voltage balancing on the remaining battery modules according to the balancing time.

[0029] Optionally, after completing voltage balancing, the method further includes:

[0030] The balancing subcircuit is controlled to switch out the energy storage subcircuit, and the switching subcircuit is controlled to reconnect the target battery module to the energy storage subcircuit.

[0031] The active balancing control circuit of the power battery pack provided in the embodiment of the present application can, by arranging a switching subcircuit, cut the battery module out of the charging / discharging circuit of the energy storage subcircuit when the voltage of the battery module in the energy storage subcircuit is abnormal during the charging / discharging period of the power battery pack, and connect the balancing subcircuit to the charging / discharging circuit, so as to maintain the load voltage and ensure voltage stability while also performing voltage balancing on the remaining battery modules through the balancing subcircuit, thereby improving the charging / discharging effect. After the battery module that has been cut out of the energy storage subcircuit returns to normal, the battery module can be reconnected to the charging / discharging circuit of the energy storage subcircuit and the charging / discharging process can be continued, thereby achieving synchronous balancing of each battery module, improving balancing efficiency, and reducing energy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 is a structural schematic diagram of an active balancing control circuit provided in an embodiment of the present application;

[0034] Figure 2 It is a partial structural diagram of an active balancing control circuit provided in an embodiment of the present application;

[0035] Figure 3 is a structural schematic diagram of another active balancing control circuit provided in an embodiment of the present application;

[0036] Figure 4 is a structural schematic diagram of another active balancing control circuit provided in an embodiment of the present application;

[0037] Figure 5is a schematic diagram of current flow of the active balancing control circuit provided in the embodiment of the present application in the charging mode;

[0038] Figure 6 is a schematic diagram of current flow in the discharge mode of the active balancing control circuit provided in an embodiment of the present application;

[0039] Figure 7 is a flow chart of an active balancing control method provided by an embodiment of the present application;

[0040] Figure 8 This is a flow chart of an active balancing control method provided in an embodiment of the present application.

[0041] Reference numerals:

[0042] 100, energy storage subcircuit; 110, battery module; 111, battery cell; 112, second switch;

[0043] 200, switching sub-circuit; 210, first switch;

[0044] 300, balancing sub-circuit; 310, third switch; 320, energy storage module; 321, primary winding; 322, fourth switch; 330, compensation module; 331, secondary winding; 332, fifth switch.

[0045] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0047] The present application embodiment provides an active balancing control circuit for a power battery pack, such as Figure 1As shown, the circuit may include: an energy storage subcircuit 100, which includes a plurality of battery modules 110 connected in series; a switching subcircuit 200, which is connected to the energy storage subcircuit 100 and is configured to control at least one battery module 110 to be switched out of or connected to the energy storage subcircuit 100; and a balancing subcircuit 300, which is used to perform voltage balancing on the remaining battery modules 110 according to the average power before balancing of each battery module 110 in the energy storage subcircuit 100 when at least one battery module 110 is switched out of the energy storage subcircuit 100 under the control of the switching subcircuit 200.

[0048] Among them, the battery module 111 "cut out" the energy storage sub-circuit 100 mentioned in the embodiment of the present application refers to disconnecting the electrical connection between the battery module 111 and the energy storage sub-circuit 100, and accordingly, the current in the charging circuit or the discharging circuit of the energy storage sub-circuit 100 will not flow through the cut-out battery module 111; at the same time, the battery module 111 in the embodiment of the present application can also be "connected" to the energy storage sub-circuit 100, that is, after being cut out, the battery module 111 can be reconnected to the energy storage sub-circuit 100, and accordingly, after the battery module 111 is reconnected to the energy storage sub-circuit 100, the current in the charging circuit or the discharging circuit of the energy storage sub-circuit 100 will flow through the battery module 111.

[0049] At present, power battery packs are usually formed by connecting multiple battery cells in series. In order to strengthen the structure and facilitate assembly, the battery cells are generally grouped into battery modules, and then multiple battery modules are further combined to form a power battery pack. Affected by the existing battery production and manufacturing process, there are differences between different battery cells, and factors such as the use environment and cyclic charge and discharge will further aggravate this difference, resulting in reduced energy efficiency of the power battery pack and even causing safety issues.

[0050] The active balancing control circuit of the power battery pack provided in the embodiment of the present application can, by arranging the switching subcircuit 200, cut out the charging / discharging circuit of the energy storage subcircuit 100 when a voltage abnormality occurs in a single or multiple battery modules 110 in the energy storage subcircuit 100 during the charging / discharging period of the power battery pack, and connect the balancing subcircuit 300 to the charging / discharging circuit, thereby maintaining the load voltage and ensuring voltage stability, and also performing voltage balancing on the remaining battery modules 110 through the balancing subcircuit 300, thereby improving the charging / discharging effect. After the battery module 110 that has been cut out of the energy storage subcircuit 100 returns to normal, the battery module 110 can be reconnected to the charging / discharging circuit of the energy storage subcircuit 100 and the charging / discharging process can be continued, thereby achieving synchronous balancing of each battery module 110, improving balancing efficiency, and reducing energy loss.

[0051] like Figure 2 As shown, in some embodiments of the present application, the switching subcircuit 200 may include a plurality of first switches 210 connected in series; each battery module 110 corresponds to a first switch 210 and is connected in parallel with the corresponding first switch 210 .

[0052] The first switch 210 is used to control the corresponding battery module 110 to connect to the energy storage sub-circuit 100 or disconnect from the energy storage sub-circuit 100. Each battery module 110 is connected in parallel with a first switch 110, so that when any battery module 110 needs to be cut out of the energy storage sub-circuit 100, the first switch 110 corresponding to the battery module 110 can be closed, so that the battery module 210 is cut out of the energy storage sub-circuit 100. Figure 2 As shown in , the circuit includes n battery modules 110 and n first switches 210. Assuming that the voltage of the nth battery module Qn is abnormal during the charging and discharging process and needs to be cut out of the energy storage sub-circuit 100, the nth first switch Sn can be closed at this time.

[0053] like Figure 2 As shown, in the embodiment of the present application, each battery module 110 may include a battery cell 111 and at least one second switch 112 , and the battery cell 111 is connected in series with the at least one second switch 112 .

[0054] Usually, if Figure 2 As shown, each battery module 110 may include a battery cell 111 and a second switch 112, and the two ends of the corresponding first switch 210 are respectively connected to a side of the battery cell 111 away from the second switch 112 and a side of the second switch 112 away from the battery cell 111. Figure 2 In the figure, symbol C is used to represent the battery cell 111 , symbol S is used to represent the first switch 210 , and symbol Q is used to represent the second switch 112 .

[0055] It should be noted that, in the embodiment of the present application, for any two battery modules 110, the relative positions between the second switches 112 and the battery cells 111 of the two battery modules 110 may be the same or different. Figure 2In the circuit structure of the energy storage subcircuit 100 shown, the relative positions of the second switches 112 and the battery cells 111 in different battery modules 110 are the same, so the current passes through the first second switch Q1, the first battery cell C1, the second second switch Q2, the second battery cell C2, the third second switch Q3, the third battery cell C3, and so on from top to bottom. Of course, in the circuit structures of some other energy storage subcircuits, the relative positions of the second switches 112 and the battery cells 111 in different battery modules 110 may also be different. For example, the current may pass through the first second switch Q1, the first battery cell C1, the second battery cell C2, the second second switch Q2, the third second switch Q3, the third battery cell C3, and so on from top to bottom.

[0056] When multiple battery cells 111 in the circuit 100 are normally charged / discharged, all the second switches 112 can be controlled to be closed, and all the first switches 210 in the switching subcircuit 200 can be controlled to be opened. When it is found that any battery cell 111 has a voltage abnormality and voltage balancing is required, the second switch 112 and the first switch 210 of the battery cell 111 can be coordinated to control the battery cell 111, so as to control the battery cell 111 to cut out of the energy storage subcircuit 100.

[0057] For example, in Figure 2 When the multiple battery cells C1-Cn in the energy storage subcircuit 100 shown in the figure are normally charged / discharged, all the second switches Q1-Qn can be controlled to be closed, and all the first switches S1-Sn in the switching subcircuit 200 can be controlled to be disconnected. When it is found that any battery cell, such as the battery cell Cn, has a voltage abnormality and needs to be cut out of the charging / discharging circuit of the energy storage subcircuit 100, the second switch Qn can be controlled to be disconnected and the first switch Sn can be closed; when the voltage equalization is completed and the battery cell Qn needs to be reconnected to the charging / discharging circuit of the energy storage subcircuit 100, the second switch Qn can be controlled to be closed and the first switch Sn can be disconnected.

[0058] like Figure 3 As shown, in some embodiments of the present application, the balancing sub-circuit 300 includes a third switch 310, an energy storage module 320 and a compensation module 330; the third switch 310 is connected in series with the energy storage sub-circuit 100; the energy storage module 320 is connected in parallel with the series-connected energy storage sub-circuit 100 and the third switch 310; the compensation module 330 is connected in parallel with the third switch 310 and is connected to the switching sub-circuit 200.

[0059] When the power battery pack is charged, the battery cells 111 in the energy storage subcircuit 100 store electrical energy, and the third switch is closed. Since the energy storage module 320 is connected in parallel with the series-connected energy storage subcircuit 100 and the third switch 310, the energy storage module 320 can also store energy at the same time. When performing voltage balancing, the third switch 310 is disconnected, and the energy in the energy storage module 320 is transmitted to the compensation module 330. At the same time, the battery cells 111 with abnormal charging voltage are cut out of the charging circuit of the energy storage subcircuit 100, and the compensation module 330 is temporarily connected to the charging circuit of the energy storage subcircuit 100 to maintain the load voltage, and at the same time, the voltage of the remaining battery cells 111 in the energy storage subcircuit 100 is balanced.

[0060] When the power battery pack is discharged, the battery cells 111 and the energy storage module 320 in the energy storage subcircuit 100 release the stored electric energy. When voltage balancing is performed, the third switch 310 is disconnected, and the energy in the energy storage module 320 is transmitted to the compensation module 330. At the same time, the battery cells 111 with abnormal discharge voltage are cut out of the discharge circuit of the energy storage subcircuit 100, and the compensation module 330 is temporarily connected to the discharge circuit of the energy storage subcircuit 100 to maintain the load voltage, and at the same time, the voltage of the remaining battery cells 111 in the energy storage subcircuit 100 is balanced.

[0061] like Figure 4 As shown, in some embodiments of the present application, the energy storage module may include a primary winding 321 and a fourth switch 322 of a transformer T, and the primary winding 321 and the fourth switch 322 are connected in series; the compensation module 330 may include a secondary winding 331 and a fifth switch 332 of a transformer T, and the secondary winding 331 and the fifth switch 332 are connected in series.

[0062] like Figure 4 As shown, the active balancing control circuit of the power battery pack provided in the embodiment of the present application may include a transformer T, the primary winding of which is connected in parallel with the energy storage sub-circuit 100, and is used to convert electrical energy into magnetic energy and store it; the secondary winding is used to be temporarily connected to the circuit to provide supplementary voltage when the battery cell with abnormal voltage is cut out of the charging and discharging circuit of the energy storage sub-circuit 100, thereby maintaining the load voltage.

[0063] In the embodiment of the present application, the coil turns ratio between the primary winding 321 and the secondary winding 331 is N1:N2=n:1, where n is the number of battery modules 110 in the energy storage subcircuit 100. Therefore, the voltage provided by the secondary winding is 1 / n of the total voltage of the energy storage subcircuit 100 before balancing, that is, the average voltage of each battery cell before balancing.

[0064] In an embodiment of the present application, the active balancing control circuit of the power battery pack may further include a power supply subcircuit 400, which is connected to the energy storage module 320 and is used to charge the energy storage module 320 and the battery cells 111 in the energy storage subcircuit 100 connected in parallel with the energy storage module 320.

[0065] During charging, the second switch 112 corresponding to the battery cell 111 cut out in the energy storage sub-circuit 100 is disconnected, and the second switches 112 corresponding to the remaining battery cells 111 are all closed; the first switch 210 corresponding to the battery cell 111 cut out in the switching sub-circuit 200 is closed, and the first switches 210 corresponding to the remaining battery cells 111 are all disconnected, the third switch 310 is closed, the fourth switch 322 is closed, and the fifth switch 332 is disconnected. At this time, except for the battery cell 111 cut out in the energy storage sub-circuit 100, the power supply circuit provides electrical energy to the remaining battery cells 111 and provides electrical energy to the energy storage module 320.

[0066] The active balancing control circuit provided in the embodiment of the present application has the following control principle:

[0067] like Figure 4 As shown, the power battery pack includes n battery cells C1-Cn, n first switches S1-Sn, and n second switches Q1-Qn.

[0068] like Figure 5As shown, in the normal charging mode, the first switch S1~Sn is first opened, and the second switch Q1~Qn and the third switch K3 are closed to charge the battery cells C1~Cn in the energy storage subcircuit. At the same time, the fourth switch K4 is closed and the fifth switch K5 is opened. The primary winding 321 of the transformer T converts electrical energy into magnetic energy and stores it. Assuming that the charging voltage of the nth battery cell Cn is detected to be too high and its remaining power is SOCn, active balancing needs to be turned on to keep the voltage of the battery cell Cn consistent with the voltages of other battery cells C1 to Cn-1, and the second switch Qn corresponding to the battery cell Cn is controlled to be disconnected, and the first switch Sn and the fifth switch K5 corresponding to the battery cell Cn are synchronously closed. Since the voltage of the primary winding 321 is equal to the total voltage of the energy storage sub-circuit 100 before balancing, the coil turns ratio N1:N2 between the primary winding 321 and the secondary winding 331 of the transformer T is n:1, so the balancing voltage that the secondary winding 331 can provide is the average voltage of each battery cell before balancing, and the balancing voltage is timely supplemented to the energy storage sub-circuit 100 to replace the voltage of the cut-out power cell Cn to maintain the load voltage. At this time, the voltage of the power battery pack is the sum of the voltages of the first n-1 battery cells C1 to Cn-1 and the balancing voltage Us provided by the secondary winding 331. During the active balancing process, the remaining power SOC1~SOCn-1 of other battery cells C1~Cn-1 that are still in the energy storage subcircuit for charging will gradually approach SOCn. When the balancing time is reached, the first switch Sn and the fifth switch K5 are disconnected, and the second switch Qn, the third switch K3 and the fourth switch K4 are closed at the same time. At this time, charging balancing is completed.

[0069] like Figure 6As shown, in the normal discharge mode, assuming that the power battery pack is fully charged and the electrical energy is converted into magnetic energy and stored in the primary winding of the transformer, the first switch S1~Sn and the fifth switch K5 are disconnected, and the second switch Q1~Qn, the third switch K3 and the fourth switch K4 are closed to discharge the battery cells C1~Cn in the energy storage subcircuit. Assuming that the discharge voltage of the first battery cell C1 is too low and its remaining power is SOC1, active balancing needs to be turned on to keep the voltage of the battery cell C1 consistent with the voltages of other battery cells C2 to Cn, and the second switch Q1, the third switch K3 and the fourth switch K4 corresponding to the battery cell C1 are controlled to be disconnected, and the first switch S1 and the fifth switch K5 corresponding to the battery cell C1 are closed at the same time. Since the voltage of the primary winding is equal to the total voltage of the energy storage sub-circuit 100 before balancing, the coil turns ratio between the primary winding 321 and the secondary winding 331 of the transformer is n:1, so the balancing voltage that the secondary winding can provide is the average voltage of each battery cell before balancing, and the balancing voltage is timely supplemented to the energy storage sub-circuit to replace the voltage of the power cell C1 that is cut off, so as to maintain the load voltage. At this time, the voltage of the battery pack is the sum of the voltages of the 2nd to nth battery cells C2 to Cn and the balancing voltage Us provided by the secondary winding. During the active balancing process, the remaining power SOC2-SOCn of other battery cells C2-Cn will gradually approach SOC1. When the balancing time is reached, the first switch S1 and the fifth switch K5 are disconnected, and the second switch Q1, the third switch K3 and the fourth switch K4 are closed at the same time. At this time, the discharge balancing is completed.

[0070] In summary, the active balancing control circuit of the power battery pack provided in the embodiment of the present application can realize that when the power battery pack is charged / discharged, when a single battery cell has an abnormal voltage, the secondary winding of the transformer is temporarily cut into the main circuit, and the load voltage is maintained stable by the voltage of the secondary winding. When the SOC of the cut-out battery cell is restored to the average SOC level of each battery cell in the battery pack, the battery cell is cut back to the charging / discharging circuit of the power battery pack through the first switch and the second switch to achieve a balancing effect, so the active balancing control circuit is highly flexible. And because the transformer has a large balancing current and a fast balancing speed, using a transformer as an energy storage conversion unit to replace a battery cell with abnormal voltage not only reduces energy loss, but also greatly improves the balancing efficiency.

[0071] An embodiment of the present application also provides an active balancing control method for a power battery pack. The method can be applied to the active balancing control circuit for a power battery pack provided in any of the above embodiments, and the executor can be a control device, such as a vehicle controller.

[0072] like Figure 7As shown, the active balancing control method of the power battery pack provided in the embodiment of the present application may include:

[0073] S1. When it is detected that there is a target battery module in the energy storage subcircuit, the average power of each battery module in the energy storage subcircuit before equalization is obtained, and the target battery module is a battery module with abnormal voltage in the charging mode or the discharging mode;

[0074] S2, controlling the switching subcircuit to cut the target battery module out of the energy storage subcircuit;

[0075] S3. Control the balancing subcircuit to balance the voltages of the remaining battery cells according to the average power of each battery module in the energy storage subcircuit before balancing.

[0076] The active balancing control method for a power battery pack provided in an embodiment of the present application can, during the charging / discharging period of the power battery pack, when it is detected that there is a target battery module in the energy storage subcircuit 100, obtain the average power of each battery module in the energy storage subcircuit before balancing, and then control the switching subcircuit to cut the target battery module out of the charging / discharging circuit of the energy storage subcircuit 100, and connect the balancing subcircuit 300 to the charging / discharging circuit, so that while maintaining the load voltage stability, the remaining battery modules 110 are voltage balanced through the balancing subcircuit 300, thereby improving the charging / discharging effect, and also improving the flexibility and balancing efficiency of active balancing.

[0077] In some embodiments of the present application, it is possible to detect whether a target battery module exists in the energy storage subcircuit in the following manner:

[0078] During the charging / discharging process of the power battery pack, the cell voltage of each battery module (the battery cells therein) is monitored in real time. When it is detected that the voltage difference between the cell voltage of one of the battery modules and the cell voltage of other battery modules is greater than the voltage difference threshold, it is determined that the charging voltage / discharging voltage of the battery module is abnormal, and the battery module is determined as the target battery module. Among them, the cell voltage of the battery cells in each battery module can be monitored and displayed by the battery management system BMS. At the same time, the BMS can also calculate the voltage difference between the cell voltages of each battery cell, so as to determine the target battery module in a timely and rapid manner. The voltage difference threshold can be set by the technician according to actual needs, for example, it can be set to 30mV.

[0079] In the embodiment of the present application, the power battery pack does not turn on active balancing during normal charging / discharging. Accordingly, the total voltage of the energy storage subcircuit before balancing refers to the sum of the cell voltages of each battery cell in the energy storage subcircuit before active balancing, which can be expressed by the following formula:

[0080] U=U C1 +U C2 +UC3 +……+U Cn =Up

[0081] Where U is the total voltage before balancing; U C1 is the cell voltage of the first battery cell, U C2 is the cell voltage of the second battery cell, and so on; Up is the primary voltage of the primary winding of the transformer.

[0082] The average power of each battery module before equalization in the energy storage subcircuit in step S1 refers to the ratio of the sum of the remaining power of each battery module in the energy storage subcircuit to the number of battery modules, which can be expressed by the following formula:

[0083] SOCaven-n=(SOC1+SOC2+SOC3+……+SOCn) / n

[0084] Among them, SOCaven-n is the average power of each battery module before equalization; SOC1 refers to the remaining power of the battery cells in the first battery module, SOC2 refers to the remaining power of the battery cells in the second battery module, and so on; n is the number of battery modules in the energy storage subcircuit.

[0085] In some embodiments of the present application, controlling the switching subcircuit to cut the target battery module out of the energy storage subcircuit includes: controlling the first switch corresponding to the target battery module to close, thereby cutting the target battery module out of the energy storage subcircuit.

[0086] The first switch corresponding to the target battery module is connected in parallel with the target battery module. Therefore, when the first switch corresponding to the target battery module is closed, it is equivalent to the target battery module being short-circuited, thereby being cut out of the energy storage sub-circuit.

[0087] like Figure 8 As shown, in some other embodiments of the present application, the battery module may include a battery cell and a second switch connected in series. Accordingly, after controlling the first switch corresponding to the target battery module to be closed, the method further includes: controlling the second switch in the target battery module to be opened.

[0088] In the embodiment of the present application, step S2 may further include steps S21 to S23.

[0089] S21. Obtain the remaining power of the target battery module.

[0090] In step S21, for example, the remaining capacity SOC of the target battery module can be obtained through the BMS. The remaining capacity SOC (State of Charge), also known as the state of charge, generally refers to the ratio of the remaining capacity of the battery after it has been used for a period of time or has been left unused for a long time to its capacity when it is fully charged, and is usually expressed as a percentage, where SOC = 0% indicates that the battery is fully discharged, and SOC = 100% indicates that the battery is fully charged.

[0091] S22: Calculate the balancing time of the balancing sub-circuit according to the remaining power of the target battery module and the average power of each battery module before balancing.

[0092] In the first case, taking charging of a power battery pack as an example, it is assumed that the nth battery module is the target battery module, the capacity of the battery cells in the target battery module is qn, the normal charging current of the target battery module is In, and the charging efficiency is β.

[0093] First, the average power of each battery module in the energy storage subcircuit before balancing can be calculated according to the remaining power of each battery module before balancing according to the following formula:

[0094] SOCaven-n=(SOC1+SOC2+SOC3+……+SOCn) / n

[0095] Among them, SOCaven-n is the average power of each battery module before equalization; SOC1 refers to the remaining power of the first battery module (middle battery cell), SOC2 refers to the remaining power of the second battery module (middle battery cell), and so on; n is the number of battery modules in the energy storage subcircuit.

[0096] Afterwards, the power △SOCn that needs to be balanced is calculated based on the remaining power SOCn of the target battery module and the average power SOCaven-n of each battery module before balancing:

[0097] △SOCn=SOCn-SOCaven-n

[0098] Finally, the equalization time tn is calculated according to the following formula:

[0099] tn=△SOCn×qn÷(β×In)

[0100] In the second case, taking the discharge of the power battery pack as an example, it is assumed that the first battery module is the target battery module, the capacity of the battery cells in the target battery module is q1, the normal charging current of the target battery module is I1, and the charging efficiency is λ.

[0101] First, the average power of each battery module in the energy storage subcircuit before balancing can be calculated according to the remaining power of each battery module before balancing according to the following formula:

[0102] SOCaven-n=(SOC1+SOC2+SOC3+……+SOCn) / n

[0103] Among them, SOCaven-n is the average power of each battery module before equalization; SOC1 refers to the remaining power of the first battery module (middle battery cell), SOC2 refers to the remaining power of the second battery module (middle battery cell), and so on; n is the number of battery modules in the energy storage subcircuit.

[0104] Afterwards, the power △SOC1 required for balancing is calculated based on the remaining power SOC1 of the target battery module and the average power SOCaven-n of each battery module before balancing:

[0105] △SOC1=SOCaven-n-SOC1

[0106] Finally, the equilibrium time t1 is calculated according to the following formula:

[0107] t1=△SOC1×q1÷(λ×I1)

[0108] S23, controlling the balancing subcircuit to perform voltage balancing on the remaining battery modules according to the balancing time.

[0109] During the charging process, the control balancing subcircuit is connected to the energy storage subcircuit for active balancing, so that the remaining power SOC1~SOCn-1 of other battery cells gradually approaches SOCn. When the balancing time tn is reached, the current charging balancing is ended. When charging, the total voltage Un of the power battery pack when the cell voltage of the nth battery module is actively balanced is: Un=U C1 +U C2 +U C3 +……+U Cn-1 +Us.

[0110] During the discharge process, the control balancing subcircuit is connected to the energy storage subcircuit for active balancing, so that the remaining power SOC2~SONn of other battery cells gradually approaches SOC1. When the balancing time t1 is reached, the current discharge balancing is ended. During discharge, when the cell voltage of the first battery module is actively balanced, the total voltage Un of the power battery pack is: Un=U C2 +U C3 +U C4 +...U cn +Us.

[0111] In some embodiments, Figure 4As shown, when controlling the balancing subcircuit to perform voltage balancing on the remaining battery modules according to the average power before balancing of each battery module in the energy storage subcircuit, the specific control steps may include:

[0112] The third switch K3 in the balancing subcircuit is controlled to be disconnected, and the energy storage module in the balancing subcircuit is controlled to be disconnected; the compensation module in the balancing subcircuit is controlled to be connected to the energy storage subcircuit, so as to provide a balancing voltage for the energy storage subcircuit, wherein the balancing time of the compensation module is tn.

[0113] In some embodiments of the present application, after completing voltage balancing, the method further includes: controlling the balancing subcircuit to switch out the energy storage subcircuit, and controlling the switching subcircuit to reconnect the target battery module to the energy storage subcircuit.

[0114] After the balancing time is reached, the voltage balancing ends. At this time, the remaining power of the battery modules remaining in the energy storage subcircuit is basically consistent with the remaining power of the target battery module. At this time, the switching subcircuit can be controlled to reconnect the target battery module to the energy storage subcircuit.

[0115] Exemplarily, during the charging process, when the balancing time tn is reached, the fifth switch K5 and the first switch Sn corresponding to the target battery module are disconnected, and the third switch K3, the fourth switch K4 and the second switch Qn corresponding to the target battery module are closed at the same time. When the current charging balancing is ended, the nth battery module is reconnected to the energy storage subcircuit and charging continues, thereby achieving a balancing effect for all battery cells.

[0116] During the discharge process, when the balancing time t1 is reached, the fifth switch K5 and the first switch S1 corresponding to the target battery module are disconnected, and the third switch K3, the fourth switch K4 and the second switch Q1 corresponding to the target battery module are closed at the same time. When the discharge balancing is ended, the first battery module is reconnected to the energy storage subcircuit and the discharge is continued, thereby achieving the balancing effect of all battery cells.

[0117] In some embodiments of the present application, after the target battery module is reconnected to the energy storage subcircuit, the method further includes: continuing to monitor whether the target battery module exists in the energy storage subcircuit, and when the target battery module is detected in the energy storage subcircuit, repeating the above steps until charging / discharging is completed.

[0118] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the present application disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only.

[0119] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. An active balancing control circuit for a power battery pack, characterized in that: The circuit comprises: An energy storage subcircuit (100) comprising a plurality of battery modules (110) connected in series; A switching subcircuit (200), connected to the energy storage subcircuit (100), and configured to control at least one battery module (110) to be switched out of or connected to the energy storage subcircuit (100); A balancing subcircuit (300) is used for performing voltage balancing on the remaining battery modules (110) according to the average power of each battery module (110) before balancing in the energy storage subcircuit (100) when the at least one battery module (110) is cut out of the energy storage subcircuit (100) under the control of the switching subcircuit (200); the balancing subcircuit (300) comprises a third switch (310), an energy storage module (320) and a compensation module (330), wherein the third switch (310) is connected in series with the energy storage subcircuit (100); the energy storage module (320) is connected to the energy storage subcircuit (100); The series-connected energy storage subcircuit (100) and the third switch (310) are connected in parallel, and the energy storage module (320) comprises a primary winding (321) of a transformer and a fourth switch (322), and the primary winding (321) and the fourth switch (322) are connected in series; the compensation module (330) is connected in parallel with the third switch (310) and is connected to the switching subcircuit (200), and the compensation module (330) comprises a secondary winding (331) of the transformer and a fifth switch (332), and the secondary winding (331) and the fifth switch (332) are connected in series.

2. The circuit according to claim 1, characterized in that The switching subcircuit (200) comprises a plurality of first switches (210) connected in series; Each of the battery modules (110) corresponds to one of the first switches (210), and is connected in parallel with the corresponding first switch (210).

3. The circuit according to claim 2, characterized in that Each of the battery modules (110) comprises a battery cell (111) and at least one second switch (112), wherein the battery cell (111) and the at least one second switch (112) are connected in series.

4. The circuit according to claim 1, characterized in that The coil turns ratio between the primary winding (321) and the secondary winding (331) is n:1, where n is the number of battery modules (110) in the energy storage subcircuit (100).

5. The circuit according to claim 1, characterized in that The circuit further comprises a power supply subcircuit (400), and the power supply subcircuit (400) is connected in parallel with the energy storage module (320).

6. An active balancing control method for a power battery pack, used in the active balancing control circuit for a power battery pack according to any one of claims 1 to 5, characterized in that: The method comprises: When it is detected that a target battery module (110) exists in the energy storage subcircuit (100), the average power of each battery module (110) in the energy storage subcircuit (100) before equalization is obtained, wherein the target battery module (110) is a battery module (110) having an abnormal voltage in a charging mode or a discharging mode; Controlling the switching subcircuit (200) to cut the target battery module (110) out of the energy storage subcircuit (100); The balancing subcircuit (300) is controlled to perform voltage balancing on the remaining battery modules (110) according to the average power of each battery module (110) before balancing in the energy storage subcircuit (100).

7. The method according to claim 6, characterized in that The controlling the balancing subcircuit (300) to perform voltage balancing on the remaining battery modules (110) according to the average power before balancing of each battery module (110) in the energy storage subcircuit (100) comprises: Acquiring the remaining power of the target battery module (110); Calculating the balancing time of the balancing subcircuit (300) according to the remaining power of the target battery module (110) and the average power of each battery module (110) before balancing; The balancing subcircuit (300) is controlled to perform voltage balancing on the remaining battery modules (110) according to the balancing time.

8. The method according to claim 6 or 7, characterized in that: After completing voltage balancing, the method further includes: The balancing subcircuit (300) is controlled to switch out the energy storage subcircuit (100), and the switching subcircuit (200) is controlled to reconnect the target battery module (110) to the energy storage subcircuit (100).

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