Method for soc equalization control of parallel battery packs and related device

Abstract

The application relates to an SOC equalization control method of a parallel battery pack and related equipment, which introduces a first voltage regulation parameter for charge-discharge current regulation and a second voltage regulation parameter for SOC equalization regulation. Since the first voltage regulation parameter is strongly related to the charge-discharge current and weakly related to the bus voltage, in the process of driving the power conversion circuit to charge and discharge the battery pack and realizing the SOC equalization control, on the one hand, the system bus voltage can be stabilized, and entering the current limiting state can be avoided, and on the other hand, the charge-discharge capacity of the battery is not limited.

Description

Technical Field

[0001] This application belongs to the field of energy storage technology, and in particular relates to a SOC equalization control method, power conversion device and energy storage device for a parallel battery pack. Background Technology

[0002] When two or more battery packs are connected in parallel, because the initial charge or the capacity of the batteries themselves is not absolutely equal, if the state of charge (SOC) of the batteries is not processed during long-term operation, the parallel SOC will differ significantly, affecting the charging and discharging capacity of the entire system. The SOC averaging algorithm in related technologies leads to two problems: firstly, it cannot stabilize the system bus voltage, causing it to enter a current-limiting state; secondly, it limits the charging and discharging capacity of the batteries. Summary of the Invention

[0003] The purpose of this application is to provide a SOC equalization control method, power conversion device and energy storage device for parallel battery packs, aiming to solve the problem that the equalization methods of related technologies cannot stabilize the system bus voltage, resulting in limited battery discharge.

[0004] In a first aspect, embodiments of this application provide a SOC equalization control method for a parallel battery pack, applicable to a first battery pack in the parallel battery pack, wherein the first battery pack is any one of the battery packs in the parallel battery pack, and each of the battery packs in the parallel battery pack is connected to a DC bus via a power conversion circuit, the SOC equalization control method comprising: The first voltage regulation parameter is determined based on the charging and discharging state and charging and discharging current of the first battery pack. The first voltage regulation parameter is used for the charging and discharging current sharing regulation of the first battery pack. A second voltage regulation parameter is determined based on the SOC of the first battery pack and the average SOC of each of the first battery packs. The second voltage regulation parameter is used for SOC equalization regulation of the first battery pack. The voltage setpoint is determined based on the first voltage adjustment parameter, the second voltage adjustment parameter, and the preset target voltage output to the DC bus. A drive signal is generated based on the given voltage, the bus voltage, and the charging / discharging current to drive the power conversion circuit. The drive signal is used to drive the power conversion circuit to draw power from the first battery pack or to charge the first battery pack.

[0005] In an optional embodiment, determining the first voltage regulation parameter based on the charge / discharge state of the first battery pack and the charge / discharge current includes: If the first battery pack is in a charging state, the charging current of the first battery pack is obtained, and the first voltage regulation parameter in the charging state is obtained based on the charging current of the first battery pack and the current sharing coefficient. If the first battery pack is in a discharging state, the discharge current of the first battery pack is obtained, and the first voltage regulation parameter in the discharging state is obtained based on the discharge current of the first battery pack and the current sharing coefficient.

[0006] The step of determining the second voltage regulation parameter based on the SOC of the first battery pack and the average SOC of all the first battery packs includes: Obtain the SOC of the first battery pack and the average SOC of each first battery pack, and subtract the two to obtain the SOC difference value; The second voltage regulation parameter is obtained based on the SOC difference and the SOC adjustment coefficient.

[0007] In an optional embodiment, generating the drive signal for driving the power conversion circuit based on the voltage setpoint, the bus voltage, and the charging / discharging current includes: Obtain the bus voltage; The given current value is calculated based on the difference between the given voltage value and the bus voltage; The duty cycle is calculated based on the difference between the given current value and the charging / discharging current. The drive signal for driving the power conversion circuit is generated based on the duty cycle.

[0008] In an optional embodiment, the sampling frequency of the bus voltage is the same as the sampling frequency of the charging and discharging current.

[0009] In an optional embodiment, the average SOC is updated at a frequency lower than the sampling frequency of the charge / discharge current.

[0010] In an optional embodiment, before calculating the duty cycle based on the difference between the given current value and the charge / discharge current, the method further includes: The given current value is limited, and the given current value is output within a preset current range; After calculating the duty cycle based on the difference between the given current value and the charging / discharging current, the method further includes: The duty cycle is limited to output a duty cycle within a preset range.

[0011] Secondly, embodiments of this application provide a power conversion device, which includes a power conversion circuit, a memory, a controller, and a computer program stored in the memory and executable on the controller. A first terminal of the power conversion circuit is used to connect to a battery pack, and a second terminal of the power conversion circuit is used to connect to a DC bus. The controller is connected to the power conversion circuit, and the controller is used to execute the computer program to implement the SOC equalization control method for parallel battery packs as described above.

[0012] In an optional embodiment, the power conversion circuit includes a boost circuit, a buck circuit, or a buck-boost circuit.

[0013] Thirdly, embodiments of this application provide an energy storage device, including a DC bus, multiple battery packs, multiple power conversion circuits, and multiple controllers. Each power conversion circuit includes a first terminal and a second terminal. Each first terminal is connected to one of the battery packs, and each second terminal is connected to the DC bus. Each controller is connected to each of the power conversion circuits in a one-to-one correspondence. The controller is used to execute the SOC equalization control method for parallel battery packs as described above.

[0014] The beneficial effects of this application embodiment compared with related technologies are as follows: The SOC equalization control method for parallel battery packs introduces a first voltage regulation parameter for charging and discharging current sharing regulation and a second voltage regulation parameter for SOC equalization regulation. Since the first voltage regulation parameter is strongly correlated with the charging and discharging current and weakly correlated with the bus voltage, and the entire equalization is performed independently by the battery pack without the need for unified regulation of the common DC bus voltage, in the process of driving the power conversion circuit to charge and discharge the battery pack and realize SOC equalization control, on the one hand, the system bus voltage can be stabilized to avoid limiting the instantaneous power of the bus and causing it to enter the current-limiting state, and on the other hand, the charging and discharging capacity of the battery will not be limited. Attached Figure Description

[0015] Figure 1 This is a connection diagram of a parallel battery pack; Figure 2 This is a schematic diagram of the structure of a battery pack provided in one embodiment of this application; Figure 3 A flowchart of a parallel battery pack SOC equalization control method provided in an embodiment of this application; Figure 4 for Figure 3 The flowchart shows the specific steps of S140 in the SOC equalization control method for parallel battery packs. Figure 5 A SOC balancing control loop diagram for a parallel battery pack provided in an embodiment of this application; Figure 6A schematic diagram of a power conversion circuit provided in an embodiment of this application; Figure 7 A schematic diagram of the SOC equalization control device for a parallel battery pack provided in an embodiment of this application; Figure 8 This is a schematic diagram of the structure of a power conversion device provided in an embodiment of this application; Figure 9 This is a schematic diagram of the structure of an energy storage device provided in an embodiment of this application. Detailed Implementation

[0016] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0017] It should be noted that when a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to that other component.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0019] like Figure 1 As shown, taking three battery packs 1, 2, and 3 connected in parallel as an example, battery packs 1, 2, and 3 are connected to each other via communication lines (not shown in the figure) and power lines. Since the different battery packs are on the same DC bus, they have essentially the same voltage. The communication lines can be connected individually to the host computer or connected together and then connected to the host computer.

[0020] Please see Figure 2 In one example, the battery pack includes battery cells and a power conversion circuit, such as a DC-DC converter. The battery cells store energy based on electrochemical principles, and the DC-DC converter performs power conversion, transferring the energy stored inside the cells to the DC bus, or transferring energy from the DC bus to the cell terminals to charge the cells, thus achieving SOC (State of Charge) equalization control. However, related SOC equalization methods are usually performed by the system's main controller, which has two drawbacks: firstly, it cannot stabilize the system bus voltage, easily entering a current-limiting state; secondly, it limits the battery's charge and discharge capabilities.

[0021] It should be noted that in other embodiments, the power conversion circuit can also be an external circuit. In this case, the battery pack may only include the battery cells and the corresponding charge / discharge switches, battery management system, etc. The power conversion circuit can be a standalone device, with one end connected to the battery pack and the other end connected to the DC bus. This application will use this as an example for subsequent descriptions, but it should be understood that the combination of the battery pack and the power conversion circuit is not limited to this.

[0022] Therefore, this application provides a SOC balancing control method for a parallel battery pack. This control method can be applied to the first battery pack in a parallel battery pack. Each battery pack in the parallel battery pack is connected to a DC bus via a power conversion circuit. This power conversion circuit can be built into the battery pack along with the battery cells, or it can be placed outside the battery pack. Please refer to... Figure 3 SOC equalization control methods include: Step S110: Determine the first voltage adjustment parameter based on the charging and discharging state and charging and discharging current of the first battery pack. The first voltage adjustment parameter is used for the charging and discharging current sharing adjustment of the first battery pack.

[0023] The first battery pack can be any of the battery packs connected in parallel, and this application does not impose any restrictions on this. The charge / discharge state of the battery pack includes a charging state and a discharging state. If the battery pack is in a charging state, the charge / discharge current refers to the charging current, and if the battery pack is in a discharging state, the charge / discharge current refers to the discharging current.

[0024] Because the battery pack exhibits bidirectional power flow, the charging current can be defined as positive and the discharging current as negative. When the battery pack discharges, a voltage droop calculated based on the discharging current is introduced; similarly, when charging, a voltage sag calculated based on the charging current is introduced. In some embodiments, the voltage droop or voltage sag introduced based on current sharing can be used as a first voltage regulation parameter.

[0025] For example, when the DC bus changes dynamically, if the discharge current of the first battery pack is greater than that of the other battery packs, the first voltage regulation parameter of the first battery pack (the discharge current is negative, and the larger the absolute value, the smaller the voltage droop) is smaller than that of the other battery packs, causing the discharge power of the first battery pack to decrease at the next moment. This ensures that no matter how the DC bus changes, the first voltage regulation parameter keeps the charging and discharging current of each battery pack as equal as possible, which is beneficial to the SOC balance among the battery packs.

[0026] Step S120: Determine the second voltage adjustment parameter based on the SOC of the first battery pack and the average SOC of each battery pack. The second voltage adjustment parameter is used for SOC equalization adjustment of the first battery pack.

[0027] For example, when the SOC of the first battery pack is higher than the average SOC, the second voltage regulation parameter of this first battery pack is greater than the second voltage regulation parameter of other battery packs, which increases the discharge power of this first battery pack at the next moment, discharges the charge faster, and the SOC can be reduced more quickly, thereby achieving an average SOC.

[0028] Step S130: Determine the voltage setpoint based on the first voltage adjustment parameter, the second voltage adjustment parameter, and the preset target voltage output to the DC bus.

[0029] This application introduces a current-sharing voltage regulation amount (i.e., the first voltage regulation parameter) and a SOC-sharing voltage regulation amount (i.e., the second voltage regulation parameter) as part of the given voltage of the voltage control loop, participating in the regulation of the entire loop variable without changing the entire control loop structure. In this way, the voltage of each battery pack can be changed by the current-sharing voltage regulation amount without changing the preset target voltage of the DC bus. The preset target voltage of the DC bus voltage does not need to be changed due to SOC balancing, thus maintaining the stable voltage of the DC bus.

[0030] Step S140: Generate a drive signal for the power conversion circuit based on the voltage setpoint, bus voltage, and charging / discharging current. The drive signal is used to drive the power conversion circuit to draw power from the first battery pack or to charge the first battery pack.

[0031] Here, the charging and discharging current refers to the charging current when the battery pack is charging and the discharging current when it is discharging. Based on the voltage setpoint, bus voltage, and charging / discharging current, a drive signal is generated to control and regulate the voltage and current control loops, generating a drive signal for the power conversion circuit. This enables the power conversion circuit to perform SOC equalization control during power intake from or charging of the first battery pack.

[0032] This method of equalizing SOC (State of Charge) control introduces voltage regulation parameters into the input of the control loop (i.e., the voltage setpoint). By adjusting the voltage setpoint of each battery pack, it regulates the charging and discharging power of each battery pack, thereby achieving SOC balance. This method does not involve changing the power setpoint or current limit. For example, the power setpoint and current limit can be set according to the maximum charging or discharging capacity of each battery pack, or according to the maximum charging or discharging capacity of the power conversion circuit. Therefore, it does not limit the charging or discharging capacity of the power conversion circuit, and thus avoids the problem of limited battery charging and discharging capacity.

[0033] In addition, it is understood that the above steps S110 and S120 can be executed sequentially, in reverse order, or simultaneously.

[0034] In an optional embodiment, step S110 includes: If the first battery pack is in a charging state, the charging current of the first battery pack is obtained, and the first voltage regulation parameter in the charging state is obtained based on the charging current of the first battery pack and the current sharing coefficient. If the first battery pack is in a discharging state, the discharge current of the first battery pack is obtained, and the first voltage regulation parameter in the discharging state is obtained based on the discharge current of the first battery pack and the current sharing coefficient.

[0035] Specifically, the current sharing voltage regulation amount is the first voltage regulation parameter: v drop =i bat *ki.

[0036] Among them, the charging current and discharging current of the first battery pack can be obtained by directly sampling the actual current i at the cell port. bat Understandably, when multiple battery packs share a bus and simultaneously affect the bus voltage, imbalances (current and voltage imbalances) among the battery packs can lead to circulating currents between them (e.g., one battery pack charging another). The root cause of these circulating currents is the voltage sampling error in the power conversion circuit. Therefore, the value of the current sharing coefficient ki is related to the voltage sampling accuracy of the entire control system. The more accurate the voltage sampling, the smaller the value of ki; conversely, the larger the system sampling error, the larger the value of ki. Furthermore, the selection of ki is also related to the maximum charging and discharging current of each battery pack. For example, defining the system voltage sampling error as Δv, the maximum charging current as Ichg_max, and the maximum discharging current as Idsg_max, the relationship between ki and Δv, Ichg_max, and Idsg_max is as follows: ki ∝ Δv / max(Ichg_max, Idsg_max).

[0037] It is important to note that the first voltage regulation parameter v drop When the maximum charging capacity and the maximum discharging capacity are asymmetrical, the first voltage regulation parameter v drop The maximum and minimum values ​​are not symmetrical about 0. By introducing a current-sharing voltage adjustment, the current sharing during parallel charging and discharging of multiple battery packs can be controlled.

[0038] In an optional embodiment, based on step S110, an adjustment amount for the average SOC is added. Specifically, step S120 includes: first, obtaining the SOC of the first battery pack and the average SOC of each battery pack, and subtracting the two to obtain the SOC difference. Then, obtaining a second voltage regulation parameter based on the SOC difference and the SOC adjustment coefficient.

[0039] Specifically, the host computer communicating with each battery pack calculates the average SOC of each battery pack and broadcasts it to each battery pack. The controller of each battery pack, for example, the first battery pack, calculates the difference between its own SOC and the average SOC, and multiplies it by the SOC adjustment factor k. soc Then, the average SOC voltage regulation introduced by the average SOC is obtained, which is the second voltage regulation parameter v. socavg When the SOC of the first battery pack (itself) is greater than the average SOC, the average SOC voltage regulation is positive; when the SOC of the first battery pack is less than the average SOC, the average SOC voltage regulation is negative. The calculation formula is as follows: v socavg =(soc n -soc avg )*k soc ; Among them, soc n For each battery pack, such as the first battery pack, the SOC (State of Charge) is... avg The average SOC of each battery pack, and the SOC adjustment coefficient k. soc The value of ksoc is also positively correlated with the system voltage sampling accuracy, that is: k soc ∝Δv / max(Ichg_max, Idsg_max) In an optional embodiment, step 130 involves adjusting the first voltage regulation parameter v. drop Second voltage regulation parameter v socavg and the preset target voltage v output to the DC bus busref The sums are used to obtain the final voltage setpoint v. ref That is, v ref =v busref +v drop +v socavg .

[0040] Please see Figure 4 In an optional embodiment, step S140 includes: Step S141: Obtain the bus voltage; Step S142: Calculate the given current value based on the difference between the given voltage value and the bus voltage; Step S143: Calculate the duty cycle based on the difference between the given current value and the charging / discharging current; Step S144: Generate the drive signal for the power conversion circuit based on the duty cycle.

[0041] Among them, the bus voltage v bus It can be detected using any traditional method. Please refer to the following for further details. Figure 5 The control processes for the voltage control loop and the current control loop are as follows: Voltage control loop: The initial reference value of the voltage control loop is the preset target voltage V. busref The first voltage regulation parameter v was introduced. drop Second voltage regulation parameter v socavg The subsequent voltage setpoint v ref This refers to the final effective target output voltage, which is the actual voltage output to the bus from each battery pack. In the voltage control loop, the actual output voltage of the DC bus, i.e., the bus voltage v, needs to be sampled. bus As the feedback voltage, it is related to the voltage setpoint v. ref The target output voltage is obtained by comparing it with the bus voltage v. bus The voltage deviation is used to calculate the given current value for the current control loop based on the first PI controller. This given current value is then passed through the first limiter to obtain the actual effective given current value i. batref This serves as the input to the current control loop. The parameters of the first limiter can be configured based on the maximum charge / discharge current of the battery pack. The first limiter is set to ensure that the charge / discharge current of the battery pack does not exceed its maximum charge / discharge capacity during loop control.

[0042] Current control loop: The reference value for the current control loop, i.e., the given current value i batref Originating from the voltage control loop. The actual current (i.e., charging / discharging current) at the sampled cell port is i. bat As the feedback current, it is related to the given current value i batref The actual output current is compared with the target output current to obtain the current deviation. The second PI controller calculates the duty cycle based on this deviation. This duty cycle is then passed through the second limiter to obtain the final effective duty cycle. The PWM modulator generates the PWM drive signal for the power conversion circuit based on this final effective duty cycle. It can be understood that the duty cycle determines the charging and discharging voltage of the battery pack. Here, the parameters of the second limiter can be configured based on the maximum charging and discharging voltage of the battery pack. The second limiter is set to limit the maximum duty cycle of the loop, ensuring that the charging and discharging voltage of the battery pack does not exceed its maximum charging and discharging capacity during loop control.

[0043] Please see Figure 6 Taking the Buck-Boost topology as an example, the power conversion circuit includes capacitor C1, MOSFETs Q1 and Q2, inductor L1, and capacitor C2. In Boost mode, the voltage gain is: V2 = V1 / (1-D2); in Buck mode, the voltage gain is: V1 = D1*V2. Here, D1 is the duty cycle of MOSFET Q1, and D2 is the duty cycle of MOSFET Q2. The aforementioned PWM stage controls the duty cycles D1 and D2 of the drive signals for MOSFETs Q1 and Q2.

[0044] In an optional embodiment, the sampling frequency of the bus voltage is the same as the sampling frequency of the charging and discharging current. Therefore, during the implementation of the above method, the first voltage regulation parameter v drop The calculation frequency of the bus voltage control loop is the same as the calculation frequency of the voltage control loop. Therefore, when the bus voltage v bus When a dynamic change occurs, causing the charging current of one battery pack to exceed the charging current of other battery packs, the first voltage regulation parameter v of that battery pack will change. drop Greater than the first voltage regulation parameter v of other battery packs drop Then the given voltage value v of this battery pack ref Greater than the given voltage value v of other battery packs ref This battery pack will reduce its charging power in the next moment, and consequently, its charging current will also decrease. This cycle continues until the charging current of this battery pack is basically the same as that of other battery packs. First voltage regulation parameter v drop It is calculated simultaneously with the voltage control loop, so that regardless of the bus voltage v bus No matter how the flow changes, the flow equalization effect can be guaranteed in real time.

[0045] In an optional embodiment, the update frequency of the average SOC is less than the sampling frequency of the charge / discharge current. This ensures that during the implementation of the above method, the second voltage regulation parameter v... socavg The update frequency is much lower than that of the first voltage regulation parameter v. drop The update frequency. Therefore, at the bus voltage v bus Even under dynamic changes, the real-time current sharing effect remains unaffected, while the bus voltage v bus Under steady-state conditions, the second voltage regulation parameter v socavg The relatively slow update frequency can still achieve the final average SOC effect.

[0046] In an optional embodiment, before step S142, the method further includes: limiting the given current value to output a given current value within a preset current range. This ensures that the given current value i... batref Within a reasonable range, to avoid excessive charging and discharging power of the battery pack.

[0047] Following step S143, the method further includes: limiting the duty cycle to output a duty cycle within a preset range. This ensures the duty cycle remains within a reasonable range, preventing excessive charging and discharging power of the battery pack.

[0048] When using the above method, there is no need for a host in the battery pack to compete for additional calculations using the above method; each battery pack can execute the above method independently. Furthermore, since there is no need to change the target value of the bus voltage, the instantaneous power of the DC bus is not limited, and there is no need to change the power setpoint or current limit of the battery pack. This allows for full utilization of the charging and discharging potential of the cells and achieves a balanced SOC effect.

[0049] Please see Figure 7 This application provides a SOC balancing control device for a parallel battery pack, comprising a first battery pack disposed in the parallel battery pack, and each of the battery packs in the parallel battery pack being connected to a DC bus via a power conversion circuit. The SOC balancing control device includes: The first acquisition module 101 is used to determine a first voltage adjustment parameter based on the charging and discharging state and charging and discharging current of the first battery pack. The first voltage adjustment parameter is used for the charging and discharging current sharing adjustment of the first battery pack. The second acquisition module 102 is used to determine a second voltage adjustment parameter based on the SOC of the first battery pack and the average SOC of each of the first battery packs. The second voltage adjustment parameter is used for SOC equalization adjustment of the first battery pack. The first calculation module 103 is used to determine the voltage setpoint based on the first voltage adjustment parameter, the second voltage adjustment parameter and the preset target voltage output to the DC bus. The second calculation module 104 is used to generate a drive signal for driving the power conversion circuit based on the voltage setpoint, the bus voltage and the charging and discharging current. The drive signal is used to drive the power conversion circuit to draw power from the first battery pack or to charge the first battery pack.

[0050] In an optional embodiment, the first acquisition module 101 includes: a first sub-acquisition unit and a second sub-acquisition unit.

[0051] If the first battery pack is in a charging state, the first sub-acquisition unit is used to acquire the charging current of the first battery pack, and obtain the first voltage regulation parameter in the charging state based on the charging current of the first battery pack and the current sharing coefficient. If the first battery pack is in a discharging state, the second sub-acquisition unit is used to acquire the discharge current of the first battery pack, and obtain the first voltage regulation parameter in the discharging state based on the discharge current of the first battery pack and the current sharing coefficient.

[0052] In an optional embodiment, the second acquisition module 102 includes: The third sub-acquisition unit is used to acquire the SOC of the first battery pack and the average SOC of each of the first battery packs, and to obtain the SOC difference by subtracting the two. The first calculation unit is used to obtain the second voltage regulation parameter based on the SOC difference and the SOC adjustment coefficient.

[0053] In an optional embodiment, the second computing module 104 includes: The fourth sub-acquisition unit is used to acquire the bus voltage; The second calculation unit is used to calculate the given current value based on the difference between the given voltage value and the bus voltage; The third calculation unit is used to calculate the duty cycle based on the difference between the given current value and the charging / discharging current. A PWM modulation unit is used to generate a drive signal for driving the power conversion circuit based on the duty cycle.

[0054] In an optional embodiment, the sampling frequency of the bus voltage is the same as the sampling frequency of the charging and discharging current.

[0055] In an optional embodiment, the average SOC is updated at a frequency lower than the sampling frequency of the charge / discharge current.

[0056] In an optional embodiment, the second calculation unit is further configured to limit the given current value and output the given current value within a preset current range.

[0057] The third calculation unit is also used to limit the duty cycle and output the duty cycle within a preset duty cycle range.

[0058] Please see Figure 8 This application also provides a power conversion device 70, which includes a power conversion circuit 71, a memory 72, a controller 73, and a computer program 721 stored in the memory 72 and executable on the controller 73. The first end of the power conversion circuit 71 is used to connect to the battery pack 701, and the second end of the power conversion circuit 71 is used to connect to the DC bus. The controller 73 is connected to the power conversion circuit 71, and when executing the computer program 721, it implements the SOC equalization control method for the parallel battery pack as described above.

[0059] In an optional embodiment, the power conversion circuit 71 includes a boost circuit, a buck circuit, or a boost-buck circuit.

[0060] Understandably, the power conversion device 70 is, for example, a standalone device used to connect to and draw power from or charge an energy storage device.

[0061] Of course, the power conversion device 70 can also be integrated into the energy storage device 80; therefore, please refer to [link / reference needed]. Figure 9 This application embodiment also provides an energy storage device 80, including a DC bus, multiple battery packs 701, multiple power conversion circuits 71, and multiple controllers 73. The power conversion circuit 71 includes a first terminal and a second terminal. Each first terminal is connected to a battery pack 701, and each second terminal is connected to the DC bus. Each controller 73 is connected to each power conversion circuit 71 in a one-to-one correspondence. The controller 73 is used to execute the SOC equalization control method of the parallel battery packs 701 as described above.

[0062] Of course, the number of battery pack 701 and power conversion circuit 71 in energy storage device 80 can also be one, and this application does not limit this.

[0063] Those skilled in the art will understand that Figure 8 , 9 The examples of power conversion device 70 and energy storage device 80 are merely examples and do not constitute a limitation on power conversion device 70 and energy storage device 80. They may include more or fewer components than shown in the figures, or combine certain components, or different components, such as input / output devices, network access devices, etc.

[0064] The controller 73 can be a central processing unit (CPU), or it can be other general-purpose controllers, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose controller can be a microcontroller or any conventional controller.

[0065] In some embodiments, memory 72 may be an internal storage unit of the power conversion device 70 or the energy storage device 80, such as a hard disk or memory of the power conversion device 70 or the energy storage device 80. In other embodiments, memory 72 may be an external storage device of the power conversion device 70 or the energy storage device 80, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the power conversion device 70 or the energy storage device 80. Furthermore, memory 72 may include both internal storage units of the power conversion device 70 or the energy storage device 80 and external storage devices. Memory 72 is used to store the operating system, applications, boot loader, data, and other programs. Memory 72 may also be used to temporarily store data that has been output or will be output.

[0066] This application also provides an electronic device, which includes: at least one controller 73, a memory 72, and a computer program 721 stored in the memory 72 and executable on the at least one controller 73. When the controller 73 executes the computer program 721, it implements the steps in any of the above-described method embodiments.

[0067] This application also provides a computer-readable storage medium storing a computer program 721, which, when executed by a controller 73, can implement the steps in the above-described method embodiments.

[0068] This application provides a computer program 721 product that, when run on a computer, causes the computer to perform the steps in the various method embodiments described above.

[0069] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above method embodiments of this application can be implemented by a computer program 721 instructing related hardware. The computer program 721 can be stored in a computer-readable storage medium. When the computer program 721 is executed by the controller 73, it can implement the steps of the above method embodiments. The computer program 721 includes computer program 721 code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable medium can include at least: any entity or device capable of carrying the computer program 721 code to the camera device / terminal device, recording medium, computer memory 72, ROM (Read-Only Memory), RAM (Random Access Memory), CD-ROM (Compact Disc Read-Only Memory), magnetic tape, floppy disk, and optical data storage device, etc. The computer-readable storage medium mentioned in this application may be a non-volatile storage medium, in other words, a non-transient storage medium.

[0070] It should be understood that all or part of the steps of the above embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented in whole or in part as a computer program 721 product. The computer program 721 product includes one or more computer instructions. The computer instructions can be stored in the above-described computer-readable storage medium.

[0071] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0072] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0073] In the embodiments provided in this application, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0074] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0075] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for SOC equalization control of a parallel battery pack, characterized in that, The first battery pack in the parallel battery pack, wherein the first battery pack is any one of the battery packs in the parallel battery pack, and each of the battery packs in the parallel battery pack is connected to the DC bus through a power conversion circuit, the SOC equalization control method includes: The first voltage regulation parameter is determined based on the charging and discharging state and charging and discharging current of the first battery pack. The first voltage regulation parameter is used for the charging and discharging current sharing regulation of the first battery pack. A second voltage regulation parameter is determined based on the SOC of the first battery pack and the average SOC of each battery pack. The second voltage regulation parameter is used for SOC equalization regulation of the first battery pack. The voltage setpoint is determined based on the first voltage adjustment parameter, the second voltage adjustment parameter, and the preset target voltage output to the DC bus. A drive signal is generated based on the voltage setpoint, the bus voltage, and the charging / discharging current to drive the power conversion circuit. The drive signal is used to drive the power conversion circuit to draw power from the first battery pack or to charge the first battery pack. The step of determining the first voltage adjustment parameter based on the charge / discharge state and charge / discharge current of the first battery pack includes: If the first battery pack is in a charging state, the charging current of the first battery pack is obtained, and the first voltage regulation parameter in the charging state is obtained based on the charging current of the first battery pack and the current sharing coefficient. If the first battery pack is in a discharging state, the discharge current of the first battery pack is obtained, and the first voltage regulation parameter in the discharging state is obtained based on the discharge current of the first battery pack and the current sharing coefficient. The step of determining the second voltage regulation parameter based on the SOC of the first battery pack and the average SOC of all the first battery packs includes: Obtain the SOC of the first battery pack and the average SOC of each first battery pack, and subtract the two to obtain the SOC difference value; The second voltage regulation parameter is obtained based on the SOC difference and the SOC adjustment coefficient.

2. The SOC balancing control method for parallel battery packs as described in claim 1, characterized in that, The step of generating a drive signal to drive the power conversion circuit based on the given voltage, the bus voltage, and the charging / discharging current includes: Obtain the bus voltage; The given current value is calculated based on the difference between the given voltage value and the bus voltage; The duty cycle is calculated based on the difference between the given current value and the charging / discharging current. The drive signal for driving the power conversion circuit is generated based on the duty cycle.

3. The SOC balancing control method for parallel battery packs as described in claim 2, characterized in that, The sampling frequency of the bus voltage is the same as the sampling frequency of the charging and discharging current.

4. The SOC balancing control method for parallel battery packs as described in claim 2 or 3, characterized in that, The update frequency of the average SOC is less than the sampling frequency of the charge / discharge current.

5. The SOC balancing control method for parallel battery packs as described in claim 2 or 3, characterized in that, Before calculating the duty cycle based on the difference between the given current value and the charging / discharging current, the method further includes: The given current value is limited, and the given current value is output within a preset current range; After calculating the duty cycle based on the difference between the given current value and the charging / discharging current, the method further includes: The duty cycle is limited to output a duty cycle within a preset range.

6. A power conversion device, characterized in that, The power conversion device includes a power conversion circuit, a memory, a controller, and a computer program stored in the memory and executable on the controller. A first terminal of the power conversion circuit is used to connect to a battery pack, and a second terminal of the power conversion circuit is used to connect to a DC bus. The controller is connected to the power conversion circuit, and when executing the computer program, the controller implements the SOC equalization control method for parallel battery packs as described in any one of claims 1 to 5.

7. The power conversion device as described in claim 6, characterized in that, The power conversion circuit includes a boost circuit, a buck circuit, or a buck-boost circuit.

8. An energy storage device, characterized in that, The device includes a DC bus, multiple battery packs, multiple power conversion circuits, and multiple controllers. Each power conversion circuit has a first terminal and a second terminal. Each first terminal is connected to one of the battery packs, and each second terminal is connected to the DC bus. Each controller is connected to each of the power conversion circuits in a one-to-one correspondence. The controller is used to execute the SOC equalization control method for parallel battery packs as described in any one of claims 1 to 5.

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