Method for soc equalization control of energy storage system and related device

Abstract

The application provides an SOC equalization control method of an energy storage system and a related device, and the method comprises the following steps: calculating a current loop output value according to a deviation value of an actual SOC value and an average SOC value of an energy storage module corresponding to a DCDC converter; adding a bus voltage given value and the current loop output value to obtain a bus voltage reference value, and subtracting an actual bus voltage value from the bus voltage reference value to obtain a bus voltage deviation value; obtaining a first control value according to the bus voltage deviation value, and taking the first control value as a current loop given value to perform closed-loop control to obtain a PWM signal for controlling the DCDC converter. By considering the deviation of the actual SOC value and the average SOC value of the current energy storage module, the application can realize current equalization control of multiple energy storage modules, avoid the situation that the SOC of each energy storage module is not balanced, and thus prolong the service life of each energy storage module.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to a SOC equalization control method and related device for an energy storage system. Background Technology

[0002] Battery energy storage systems primarily utilize batteries to store electrical energy. Traditional battery energy storage systems typically consist of multiple battery clusters connected in parallel. Each battery cluster usually requires multiple battery packs connected in series, and the more battery packs connected in series, the greater the impact of each individual battery pack on the energy storage system.

[0003] Traditional energy storage system charging and discharging control methods, such as droop control, can usually only ensure normal grid connection of multiple energy storage modules, but cannot ensure current sharing control of each energy storage module. This leads to uneven power distribution among the energy storage modules and affects their service life. Summary of the Invention

[0004] In view of this, the present invention provides a SOC (State of Charge) balancing control method and related device for an energy storage system, which can solve the problem of SOC imbalance among multiple energy storage modules.

[0005] In a first aspect, embodiments of the present invention provide a SOC equalization control method for an energy storage system, wherein the energy storage system includes multiple DC-DC converters and multiple energy storage modules, and the first end of each DC-DC converter is connected to a common DC bus, and the second end is connected to an energy storage module.

[0006] The method is applied to the DC-DC converter, including:

[0007] Obtain the actual value of the bus voltage of the DC-DC converter and the actual SOC value of the energy storage module corresponding to the DC-DC converter;

[0008] The current sharing loop output is calculated based on the deviation between the actual SOC value and the average SOC value, where the average SOC value is the average of the SOC values ​​of all energy storage modules in the energy storage system.

[0009] The bus voltage setpoint is added to the output of the current sharing ring to obtain the bus voltage reference value, and the actual bus voltage value is subtracted from the bus voltage reference value to obtain the bus voltage deviation value.

[0010] The first control value is obtained based on the bus voltage deviation value, and the first control value is used as the current loop setpoint for closed-loop control to obtain the PWM signal for controlling the DC-DC converter.

[0011] In a second aspect, embodiments of the present invention provide a DC-DC converter, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method as described in any possible implementation of the first aspect above.

[0012] Thirdly, embodiments of the present invention provide a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method as described in any possible implementation of the first aspect above.

[0013] Fourthly, embodiments of the present invention provide an energy storage system, which includes: a battery management module, a plurality of DC-DC converters as described in the second aspect, and a plurality of energy storage modules; the energy storage module includes a plurality of individual battery cells; the battery management module includes a cell management unit corresponding to each individual battery cell, a battery cluster management unit corresponding to each energy storage module, and a system-level management unit;

[0014] Each DC-DC converter has its first terminal connected to a common DC bus and its second terminal connected to an energy storage module.

[0015] The cell management unit, the battery cluster management unit, and the system-level management unit are interconnected; the battery cluster management unit is connected to the corresponding DC-DC converter via a dry contact.

[0016] The beneficial effects of the embodiments of the present invention compared with the prior art are as follows:

[0017] This embodiment of the invention calculates the current sharing loop output based on the deviation between the actual SOC value and the average SOC value of the energy storage module corresponding to the DC-DC converter. The bus voltage setpoint is added to the current sharing loop output to obtain a bus voltage reference value. The actual bus voltage value is then subtracted from the reference value to obtain the bus voltage deviation value. A first control value is obtained based on this deviation value, and this first control value is used as the current loop setpoint for closed-loop control to obtain the PWM signal controlling the DC-DC converter. This embodiment, by considering the deviation between the actual and average SOC values ​​of the current energy storage module, enables current sharing control of multiple energy storage modules, avoiding SOC imbalances among the modules and thus extending the lifespan of each module. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a structure of an energy storage system provided in an embodiment of the present invention;

[0020] Figure 2 This is another structural schematic diagram of the energy storage system provided in the embodiment of the present invention;

[0021] Figure 3 This is a flowchart illustrating the implementation of the SOC equalization control method for an energy storage system provided in this embodiment of the invention.

[0022] Figure 4 This is a circuit diagram of a DC-DC converter provided in an embodiment of the present invention;

[0023] Figure 5 This is a specific control block diagram of the SOC equalization control method for an energy storage system provided in this embodiment of the invention;

[0024] Figure 6 This is a schematic diagram of the SOC equalization control device of the energy storage system provided in an embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the DC-DC converter provided in an embodiment of the present invention. Detailed Implementation

[0026] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0028] This embodiment provides an energy storage system, which includes multiple DC-DC converters and multiple energy storage modules, wherein the first end of each DC-DC converter is connected to a common DC bus, and the second end is connected to the energy storage module.

[0029] As a specific embodiment of this application, Figure 1A schematic diagram of an energy storage system is shown, in which multiple energy storage modules are connected to the grid via a bus parallel connection. Figure 1 As shown, the energy storage system includes an energy storage converter DC / AC, multiple DC-DC converters, and multiple energy storage modules BAT. The first end of each DC-DC converter is connected to a common DC bus DC_BUS, and the second end of each DC-DC converter is connected to its corresponding energy storage module BAT. The common DC bus DC_BUS is connected to the grid GRID through the energy storage converter DC / AC.

[0030] As a specific embodiment of this application, Figure 2 Another schematic diagram of an energy storage system is shown, in which multiple energy storage modules are connected to the grid in parallel at both ends. For example... Figure 2 As shown, the energy storage system includes an energy storage converter (DC / AC), multiple DC-DC converters, and multiple energy storage modules (BAT). The first terminal of each DC-DC converter is connected to a common DC bus (DC_BUS), and the second terminal of each DC-DC converter is connected in parallel to all the energy storage modules (BAT). The common DC bus (DC_BUS) is connected to the grid (GRID) through the energy storage converter (DC / AC).

[0031] The SOC equalization control method for energy storage systems provided in this embodiment is applied to any DC-DC converter in the energy storage system. (See also...) Figure 3 The flowchart illustrating the implementation of the SOC equalization control method for an energy storage system provided in this embodiment of the invention is described in detail below:

[0032] S101: Obtain the actual value of the bus voltage of the DC-DC converter and the actual SOC value of the energy storage module corresponding to the DC-DC converter.

[0033] In this embodiment, as Figure 4 As shown, Figure 4 A circuit diagram of a DC-DC converter is shown, wherein, Figure 4 The right side of the circuit represents the first terminal of the DC-DC converter, and the left side represents the second terminal. First, obtain the actual value V of the DC-DC converter's bus voltage. bus_fdb And the actual SOC value of the energy storage module corresponding to the DC-DC converter.

[0034] S102: Calculate the current sharing loop output based on the deviation between the actual SOC value and the average SOC value, where the average SOC value is the average of the SOC values ​​of all energy storage modules in the energy storage system.

[0035] In one embodiment, the specific implementation process of S102 includes:

[0036] S201: Calculate the bus current setpoint based on the deviation between the actual SOC value and the average SOC value;

[0037] S202: Calculate the bus current deviation value based on the actual value of the bus current and the given value of the bus current of the DC-DC converter;

[0038] S203: Input the bus current deviation value into the first PI controller to obtain the current sharing loop output.

[0039] The specific implementation process of S201 includes:

[0040] According to Formula I bus_ref =I bus_ave +K1·ΔSOC, calculate the given value of the bus current;

[0041] Among them, I bus_ref I represents the given value of the bus current. bus_ave K1 represents the average value of the actual bus current of each DC-DC converter, K1 represents the current sharing ring coefficient, and ΔSOC represents the deviation between the actual SOC value and the average SOC value.

[0042] Specifically, ΔSOC = SOC self -SOC ave Among them, SOC self This represents the actual SOC value. ave This represents the average SOC value. K1 is the current sharing ring coefficient, which represents the adjusted bus current deviation value corresponding to each 1% deviation in the SOC value.

[0043] When energy storage systems are like Figure 1 As shown, each energy storage module has a different actual SOC value, and the bus current setpoint can be obtained based on the above formula. When the energy storage system is as follows... Figure 2 As shown, since the output terminals of each energy storage module are connected in parallel, the SOC values ​​of each energy storage module are equal, that is, the actual SOC value minus the average SOC value equals zero. Therefore, the bus current setpoint is the average of the actual bus current values ​​of each DC-DC converter.

[0044] Specifically, Figure 5 A block diagram of SOC equalization control for an energy storage system is shown, such as... Figure 5 As shown, after obtaining the bus current setpoint I bus_ref Then, set the bus current value I. bus_ref Subtract the actual value of the bus current I bus_fdb The bus current deviation value is obtained. Then, the bus current deviation value is input into the first PI controller to obtain the current sharing loop output I. ave_out .

[0045] S103: Set the bus voltage setpoint V bus_ref With the output I of the current sharing ring ave_out The values ​​are added together to obtain a reference value for the bus voltage, and the actual value of the bus voltage V is subtracted from the reference value. bus_fdb The bus voltage deviation value is obtained.

[0046] S104: Obtain a first control quantity based on the bus voltage deviation value, and use the first control quantity as the current loop setpoint for closed-loop control to obtain the PWM signal for controlling the DC-DC converter.

[0047] Specifically, such as Figure 5 As shown, the specific implementation process of S104 includes:

[0048] The bus voltage deviation value is input into the fourth PI controller to obtain the first control quantity.

[0049] In one embodiment, such as Figure 5 As shown, before using the first control quantity as the current loop setpoint for closed-loop control, the SOC equalization control method provided in this embodiment further includes:

[0050] S301: Obtain the actual battery voltage V of the energy storage module corresponding to the DC-DC converter. bat_fdb ;

[0051] S302: Based on the actual battery voltage value V bat_fdb and battery voltage setpoint V bus_ref The deviation value is used to calculate the second control variable;

[0052] S303: Reverse the second control quantity to obtain the third control quantity.

[0053] The specific implementation process of S302 includes:

[0054] The battery voltage setpoint V bus_ref Subtract the actual value of the battery voltage V bat_fdb The battery voltage deviation value is obtained;

[0055] The battery voltage deviation value is input into the second PI controller to obtain the second control quantity.

[0056] Specifically, the battery voltage setpoint can be the equalization charging voltage. During the charging process, the third control quantity and the first control quantity output by the battery voltage loop are compared, and the larger value of the two is selected as the final current loop setpoint. This avoids overcharging caused by a small current loop setpoint leading to a large duty cycle of the buck switch, thereby achieving battery voltage regulation during the charging process.

[0057] Accordingly, the first control quantity is used as the current loop setpoint for closed-loop control to obtain the PWM signal controlling the DC-DC converter, including:

[0058] The larger of the first control value and the third control value is used as the current loop setpoint for closed-loop control to obtain the PWM signal controlling the DC-DC converter.

[0059] In one possible embodiment, such as Figure 5 As shown, after obtaining the current loop setpoint, this embodiment can also limit the current loop setpoint according to the current limiting / derating standard of the power management system; and generate a PWM signal to control the DC-DC converter based on the limited current loop setpoint.

[0060] Specifically, such as Figure 5 As shown, the specific implementation process of S104 includes:

[0061] S401: Obtain the inductor current Il_fdb of the DC-DC converter;

[0062] S402: Calculate the difference between the inductor current Il_fdb and the current loop setpoint to obtain the current loop deviation value;

[0063] S403: Input the current loop deviation value into the third PI controller to obtain the target control quantity;

[0064] S404: Generate a PWM signal to control the DC-DC converter based on the target control quantity.

[0065] In one embodiment, the specific implementation process of S404 includes:

[0066] The target control quantity is modulated to obtain a PWM signal that controls the boost switch in the DC-DC converter;

[0067] The target control quantity is inverted and then modulated to obtain a PWM signal that controls the buck switch in the DC-DC converter.

[0068] Specifically, after obtaining the target control quantity, such as Figures 4 to 5 As shown, the target control quantity is divided by the actual value of the bus voltage V. bus The fourth control quantity is obtained, and the fourth control quantity is modulated to obtain the PWM signal controlling the boost switches Q1 and Q2 in the DC-DC converter; the fourth control quantity is inverted, and the inverted fourth control quantity is modulated to obtain the PWM signal controlling the buck switches Q3 and Q4 in the DC-DC converter.

[0069] The SOC equalization control method provided in this embodiment results in a large SOC deviation when the actual SOC value of the energy storage module is larger than the average SOC value, leading to a larger output of the current sharing loop. After adding the output of the current sharing loop to the bus voltage setpoint, if the energy storage module is in a charging state, the duty cycle of the buck switch decreases, raising the bus voltage of the energy storage module. However, the bus voltage of the common DC bus remains unchanged, resulting in less charging of the energy storage module. Conversely, if the energy storage module is in a discharging state, the duty cycle of the boost switch increases, raising the bus voltage. However, the bus voltage of the common DC bus remains unchanged, resulting in more discharging of the energy storage module. When the actual SOC value of the energy storage module is smaller than the average SOC value, the SOC deviation is smaller, resulting in a smaller output of the current sharing loop. After adding the output of the current sharing loop to the bus voltage setpoint, if the energy storage module is charging, the duty cycle of the buck converter increases, the bus voltage decreases, but the bus voltage of the common DC bus remains unchanged, so the energy storage module will charge more. If the energy storage module is discharging, the duty cycle of the boost converter decreases, the bus voltage decreases, but the bus voltage of the common DC bus remains unchanged, so the energy storage module will discharge less. Therefore, the SOC balancing control method provided in this embodiment can, when multiple energy storage modules are connected to the grid, ensure that energy storage modules with high SOC values ​​discharge more and charge less, and energy storage modules with low SOC values ​​charge more and discharge less. Furthermore, it makes linear adjustments based on the SOC deviation value, avoiding the bottleneck effect of the energy storage system and improving the service life of the energy storage modules.

[0070] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0071] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0072] Figure 6 A schematic diagram of the SOC equalization control device for an energy storage system provided in an embodiment of the present invention is shown. The energy storage system includes multiple DC-DC converters and multiple energy storage modules. The first terminal of each DC-DC converter is connected to a common DC bus, and the second terminal is connected to an energy storage module. For ease of explanation, Figure 6 Only the parts relevant to the embodiments of the present invention are shown, and are described in detail below:

[0073] The SOC balancing control device 100 of the energy storage system includes:

[0074] Data acquisition module 110 is used to acquire the actual value of the bus voltage of the DC-DC converter and the actual SOC value of the energy storage module corresponding to the DC-DC converter.

[0075] The current sharing loop output acquisition module 120 is used to calculate the current sharing loop output based on the deviation between the actual SOC value and the average SOC value, wherein the average SOC value is the average value of the SOC values ​​of all energy storage modules in the energy storage system.

[0076] The bus voltage deviation calculation module 130 is used to add the bus voltage setpoint to the output of the current sharing ring to obtain the bus voltage reference value, and to subtract the actual bus voltage value from the bus voltage reference value to obtain the bus voltage deviation value.

[0077] The PWM signal generation module 140 is used to obtain a first control quantity based on the bus voltage deviation value, and use the first control quantity as the current loop setpoint for closed-loop control to obtain the PWM signal for controlling the DC-DC converter.

[0078] In one possible embodiment, the current sharing loop output acquisition module 120 includes:

[0079] The bus current setpoint calculation unit is used to calculate the bus current setpoint based on the deviation between the actual SOC value and the average SOC value.

[0080] The bus current deviation calculation unit is used to calculate the bus current deviation value based on the actual value of the bus current and the given value of the bus current of the DC-DC converter.

[0081] The current sharing loop output calculation unit is used to input the bus current deviation value into the first PI controller to obtain the current sharing loop output.

[0082] In one possible embodiment, the bus current setpoint calculation unit includes:

[0083] According to Formula I bus_ref =I bus_ave +K1·ΔSOC, calculate the given value of the bus current;

[0084] Among them, I bus_ref I represents the given value of the bus current. bus_ave K1 represents the average value of the actual bus current of each DC-DC converter, K1 represents the current sharing ring coefficient, and ΔSOC represents the deviation between the actual SOC value and the average SOC value.

[0085] In one possible embodiment, the SOC balancing control device 100 of the energy storage system further includes a third control quantity calculation module, used for:

[0086] A battery voltage acquisition unit is used to acquire the actual battery voltage value of the energy storage module corresponding to the DC-DC converter;

[0087] The second control quantity calculation unit is used to calculate the second control quantity based on the deviation between the actual value of the battery voltage and the given value of the battery voltage.

[0088] The third control quantity calculation unit is used to reverse the second control quantity to obtain the third control quantity;

[0089] Accordingly, the PWM signal generation module 140 includes:

[0090] The larger of the first control value and the third control value is used as the current loop setpoint for closed-loop control to obtain the PWM signal controlling the DC-DC converter.

[0091] In one possible embodiment, the second control quantity calculation unit includes:

[0092] Subtracting the actual battery voltage value from the given battery voltage value yields the battery voltage deviation value.

[0093] The battery voltage deviation value is input into the second PI controller to obtain the second control quantity.

[0094] In one possible embodiment, the PWM signal generation module 140 includes:

[0095] An inductor current acquisition unit is used to acquire the inductor current of the DC-DC converter;

[0096] The current loop deviation calculation unit is used to calculate the difference between the inductor current and the current loop setpoint to obtain the current loop deviation value.

[0097] The target control quantity calculation unit is used to input the current loop deviation value into the third PI controller to obtain the target control quantity;

[0098] A modulation unit is used to generate a PWM signal for controlling the DC-DC converter based on the target control quantity.

[0099] In one possible embodiment, the modulation unit includes:

[0100] The target control quantity is modulated to obtain a PWM signal that controls the boost switch in the DC-DC converter;

[0101] The target control quantity is inverted and then modulated to obtain a PWM signal that controls the buck switch in the DC-DC converter.

[0102] Through the above solution, this application can achieve current sharing control of multiple energy storage modules, avoid the situation of unbalanced SOC of each energy storage module, and thus extend the service life of each energy storage module.

[0103] The SOC equalization control device for the energy storage system provided in this embodiment can be used to execute the SOC equalization control method embodiment of the above-mentioned energy storage system. Its implementation principle and technical effect are similar, and will not be described again here.

[0104] Figure 7 This is a schematic diagram of a DC-DC converter provided in an embodiment of the present invention. Figure 7 As shown, the DC-DC converter 7 of this embodiment includes: a processor 70, a memory 71, and a computer program 72 stored in the memory 71 and executable on the processor 70. When the processor 70 executes the computer program 72, it implements the steps in the above-described embodiments of the SOC equalization control method for various energy storage systems, for example... Figure 3 Steps 101 to 104 are shown. Alternatively, when the processor 70 executes the computer program 72, it implements the functions of each module / unit in the above-described device embodiments, for example... Figure 6 The functions of modules 110 to 140 are shown.

[0105] For example, the computer program 72 can be divided into one or more modules / units, which are stored in the memory 71 and executed by the processor 70 to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program 72 in the DC-DC converter 7.

[0106] The DC-DC converter 7 may include, but is not limited to, a processor 70 and a memory 71. Those skilled in the art will understand that... Figure 7 This is merely an example of DC-DC converter 7 and does not constitute a limitation on DC-DC converter 7. It may include more or fewer components than shown, or combine certain components, or different components. For example, the DC-DC converter may also include input / output devices, network access devices, buses, etc.

[0107] The processor 70 may be a Central Processing Unit (CPU), or other general-purpose processors, 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. A general-purpose processor may be a microprocessor or any conventional processor.

[0108] The memory 71 can be an internal storage unit of the DC-DC converter 7, such as a hard disk or RAM of the DC-DC converter 7. The memory 71 can also be an external storage device of the DC-DC converter 7, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the DC-DC converter 7. Furthermore, the memory 71 can include both internal storage units and external storage devices of the DC-DC converter 7. The memory 71 is used to store the computer program and other programs and data required by the DC-DC converter. The memory 71 can also be used to temporarily store data that has been output or will be output.

[0109] This invention provides an energy storage system, comprising: a battery management module, multiple DC-DC converters as described above, and multiple energy storage modules; each energy storage module includes multiple individual battery cells; the battery management module includes a cell management unit corresponding to each individual battery cell, a battery cluster management unit corresponding to each energy storage module, and a system-level management unit.

[0110] Each DC-DC converter has its first terminal connected to a common DC bus and its second terminal connected to an energy storage module.

[0111] The cell management unit, the battery cluster management unit, and the system-level management unit are interconnected; the battery cluster management unit is connected to the corresponding DC-DC converter via a dry contact.

[0112] In this embodiment, the energy storage system also includes a power conversion system (PCS). The DC terminal of the power conversion system is connected to a common DC bus, and the AC terminal is used to connect to the power grid.

[0113] The energy storage system uses a three-tier architecture consisting of a cell management unit, a battery cluster management unit, and a system-level management unit to control the power-on and tripping of the DC-DC converter.

[0114] Specifically, the cell management unit collects the voltage and temperature of the corresponding individual cell and sends the voltage and temperature of the individual cell to the battery cluster management unit. The battery cluster management unit collects the total voltage and main circuit current data of the energy storage module and sends the voltage and temperature of the individual cell, the total voltage and main circuit current data of the energy storage module to the system-level management unit. The system-level management unit determines whether the energy storage module has failed based on the voltage and temperature of the individual cell and the total voltage and main circuit current data of the energy storage module, and issues a fault diagnosis and protection command to the cell management unit or the battery cluster management unit when a fault occurs.

[0115] The dry contacts between the DC-DC converter and the battery cluster management unit include fault dry contacts and contactor power dry contacts.

[0116] The battery cluster management unit determines how to control the DC-DC converter based on the fault type. If the fault is not serious, it controls the DC-DC converter to respond to the fault protection command via the bus. If it is a serious fault, it activates the fault dry contact, and the DC-DC converter responds and stops running. If it does not respond, it activates the contactor power dry contact, disconnects the main circuit contactor, and thus stops the battery system.

[0117] Furthermore, the system-level management unit communicates with the liquid chiller unit via RS485 and is also connected to the disconnect switch feedback, water immersion feedback, emergency stop feedback, and fire alarm via dry contacts.

[0118] Furthermore, the energy storage system has four external outputs: one is the CAN bus communication between the system-level management unit and the PCS (Process Control System, bidirectional energy storage inverter); one is the Ethernet communication between the system-level management unit and the external network; one is the dry contact between the system-level management unit and the PCS; and one is the emergency stop fault dry contact between the system-level management unit and the external network.

[0119] Through the above solution, this embodiment can not only achieve comprehensive information interaction in the energy storage system, but also realize SOC balance control between energy storage modules, thereby improving the stability of the energy storage system.

[0120] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0121] 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.

[0122] 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 implementations should not be considered beyond the scope of this invention.

[0123] In the embodiments provided by this invention, it should be understood that the disclosed device / DC-DC converter and method can be implemented in other ways. For example, the device / DC-DC converter 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 mutual 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.

[0124] 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.

[0125] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0126] If the integrated module / 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 embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium. When executed by a processor, the computer program can implement the steps of the SOC equalization control method embodiments of the various energy storage systems described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. It should be noted that the content contained in the computer-readable medium may be appropriately added to or subtracted from the content as required by the legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium may not include electrical carrier signals and telecommunication signals.

[0127] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A SOC equalization control method for an energy storage system, characterized in that, The energy storage system includes multiple DC-DC converters and multiple energy storage modules, with the first end of each DC-DC converter connected to a common DC bus and the second end connected to an energy storage module. The method is applied to the DC-DC converter, including: Obtain the actual value of the bus voltage of the DC-DC converter and the actual SOC value of the energy storage module corresponding to the DC-DC converter; The current sharing loop output is calculated based on the deviation between the actual SOC value and the average SOC value, where the average SOC value is the average of the SOC values ​​of all energy storage modules in the energy storage system. The bus voltage setpoint is added to the output of the current sharing ring to obtain the bus voltage reference value, and the actual bus voltage value is subtracted from the bus voltage reference value to obtain the bus voltage deviation value. The first control value is obtained based on the bus voltage deviation value, and the first control value is used as the current loop setpoint for closed-loop control to obtain the PWM signal for controlling the DC-DC converter. The step of using the first control quantity as a current loop setpoint for closed-loop control to obtain a PWM signal for controlling the DC-DC converter includes: Obtain the inductor current of the DC-DC converter; Calculate the difference between the inductor current and the current loop setpoint to obtain the current loop deviation value; The current loop deviation value is input into the third PI controller to obtain the target control quantity; The PWM signal for controlling the DC-DC converter is generated based on the target control quantity.

2. The SOC equalization control method for an energy storage system as described in claim 1, characterized in that, The calculation of the current sharing loop output based on the deviation between the actual SOC value and the average SOC value includes: The bus current setpoint is calculated based on the deviation between the actual SOC value and the average SOC value. Calculate the bus current deviation value based on the actual bus current value and the given bus current value of the DC-DC converter; The bus current deviation value is input into the first PI controller to obtain the output of the current sharing loop.

3. The SOC equalization control method for an energy storage system as described in claim 2, characterized in that, The calculation of the bus current setpoint based on the deviation between the actual SOC value and the average SOC value includes: The bus current setpoint is calculated according to the formula Ibus_ref=Ibus_ave+K1·ΔSOC; Wherein, Ibus_ref represents the given value of the bus current, Ibus_ave represents the average value of the actual bus current of each DC-DC converter, K1 represents the current sharing loop coefficient, and ΔSOC represents the deviation between the actual SOC value and the average SOC value.

4. The SOC equalization control method for an energy storage system as described in claim 1, characterized in that, Before using the first control quantity as a current loop setpoint for closed-loop control to obtain the PWM signal controlling the DC-DC converter, the method further includes: Obtain the actual battery voltage value of the energy storage module corresponding to the DC-DC converter; The second control quantity is calculated based on the deviation between the actual battery voltage value and the given battery voltage value; The second control quantity is reversed to obtain the third control quantity; Accordingly, the step of using the first control quantity as a current loop setpoint for closed-loop control to obtain a PWM signal for controlling the DC-DC converter includes: The larger of the first control value and the third control value is used as the current loop setpoint for closed-loop control to obtain the PWM signal controlling the DC-DC converter.

5. The SOC equalization control method for an energy storage system as described in claim 4, characterized in that, The step of calculating the second control quantity based on the deviation between the actual battery voltage value and the given battery voltage value includes: Subtracting the actual battery voltage value from the given battery voltage value yields the battery voltage deviation value. The battery voltage deviation value is input into the second PI controller to obtain the second control quantity.

6. The SOC equalization control method for an energy storage system as described in claim 1, characterized in that, The step of generating a PWM signal to control the DC-DC converter based on the target control quantity includes: The target control quantity is modulated to obtain a PWM signal that controls the boost switch in the DC-DC converter; The target control quantity is inverted and then modulated to obtain a PWM signal that controls the buck switch in the DC-DC converter.

7. A DC-DC converter, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 6 above.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 6 above.

9. An energy storage system, characterized in that, include: The battery management module includes multiple DC-DC converters as described in claim 7 and multiple energy storage modules; the energy storage module includes multiple individual battery cells; the battery management module includes a cell management unit corresponding to each individual battery cell, a battery cluster management unit corresponding to each energy storage module, and a system-level management unit. Each DC-DC converter has its first terminal connected to a common DC bus and its second terminal connected to an energy storage module. The cell management unit, the battery cluster management unit, and the system-level management unit are interconnected; the battery cluster management unit is connected to the corresponding DC-DC converter via a dry contact.

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