A soc equalization control method and device for a cascade energy storage

Abstract

A kind of SOC equalization control method and device of cascade energy storage, characterized in that, the method includes the following steps: step 1, pre-test battery pack in cascade energy storage, and extract the characteristic parameter of each unit battery in the battery pack, and based on the characteristic parameter, construct the fitting function between the health state of each unit battery and charge-discharge voltage;Step 2, the characteristic point in the fitting function is recorded in the estimation control table, and the charge-discharge voltage of each unit battery in the battery pack is monitored in real time, to query the characteristic point in the estimation control table based on the charge-discharge voltage;Step 3, based on the characteristic point obtained by inquiry, the health state of each unit battery in the battery pack is obtained, and the feedback control unit of the cascade energy storage is adjusted, to realize the stable output of the cascade energy storage.The application improves the equalization speed and reduces the consistency requirement of ladder battery.

Description

Technical Field

[0001] This invention relates to the field of power systems, and more specifically, to a SOC equalization control method and system for cascaded energy storage. Background Technology

[0002] In recent years, with the rapid development of battery technology, battery costs have generally decreased. At the same time, the rapid development of electric vehicles has led to a year-on-year increase in the number of retired batteries. If these retired batteries are not properly utilized and disposed of, it will not only waste resources but also cause significant environmental damage. Applying retired power batteries as energy storage devices to all aspects of power generation, transmission, distribution, and consumption can stabilize power plant output, improve generator operating efficiency, ensure power quality, solve the problem of power battery recycling, save resources, protect the environment, and improve economic efficiency.

[0003] Battery packing technology allows a large number of batteries to be directly connected in series and parallel to meet voltage and capacity requirements before being connected to an inverter. Because inconsistencies in battery production and usage can affect the capacity and energy efficiency of the battery pack, battery packing places extremely high demands on the consistency of individual battery cells. To reduce the consistency requirements of battery storage systems and improve the capacity and energy efficiency of the battery pack, the charging and discharging power of each battery module can be controlled individually, ensuring that all batteries reach a fully charged or fully discharged state as simultaneously as possible. Applying power electronics and battery management technologies to battery packing divides the originally large number of directly connected series and parallel batteries into several low-voltage battery packs. Based on a cascaded multilevel inverter, power electronic devices are combined with the low-voltage battery packs to form modules, enabling independent control of each battery module. This reduces the consistency requirements of the battery pack and improves the capacity and energy efficiency of the battery pack. This battery packing method is also known as flexible packing technology.

[0004] However, existing flexible battery pack technologies typically only determine the output state of the energy storage battery during power exchange with the external grid based on basic parameters such as the overall voltage and current of the integrated battery pack. While this approach is relatively simple, when some batteries in the cascaded battery pack fail or experience a decline in health leading to unstable output, traditional control methods struggle to maintain the converter's output state. This results in poor battery pack output stability, low system flexibility, difficulty in accurately predicting the battery pack's grid-connected performance, and an inability to support the grid's broader output requirements for energy storage during grid connection.

[0005] To address the aforementioned issues, a novel energy storage control method and device are proposed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a SOC equalization control method and device for cascaded energy storage. By testing the battery pack, the characteristic parameters of each cell in the battery pack are obtained, and the correlation between the battery's health state and its charge / discharge voltage is fitted. This correlation enables real-time control of the battery pack's output state.

[0007] The present invention adopts the following technical solution. In its first aspect, the present invention relates to a SOC equalization control method for cascaded energy storage, the method comprising the following steps: Step 1, pre-testing the battery pack in the cascaded energy storage, extracting characteristic parameters of each cell in the battery pack, and constructing a fitting function between the health state and charge / discharge voltage of each cell based on the characteristic parameters; Step 2, recording the characteristic points in the fitting function in an estimation control table, and monitoring the charge / discharge voltage of each cell in the battery pack in real time, so as to query the characteristic points in the estimation control table based on the charge / discharge voltage; Step 3, based on the queried characteristic points, obtaining the health state of each cell in the battery pack, and adjusting the feedback control unit of the cascaded energy storage to achieve stable output of the cascaded energy storage.

[0008] Preferably, the tests include battery capacity testing, hybrid power pulse capability testing, and low-rate battery charge-discharge testing.

[0009] Preferably, the characteristic parameters include charge / discharge voltage, battery capacity, battery charge level, battery internal resistance, remaining cycle count, battery temperature, and current rate.

[0010] Preferably, the health status of the cell is calculated based on the characteristic parameters.

[0011] Preferably, the fitting function is a linear fitting function; and, based on the charge and discharge duration of the unit battery, the fitting function of the unit battery under different charge and discharge durations is obtained respectively.

[0012] Preferably, the estimation control table is used to record the one-to-one correspondence between the cell number, charge / discharge duration, charge / discharge voltage, and health status.

[0013] Preferably, the feature points in the estimation control table are obtained based on the values ​​of the fitting function under uniformly distributed health status.

[0014] Preferably, the estimation control table is stored in the energy storage monitoring unit and is called in real time by the feedback control unit in the cascaded energy storage.

[0015] Preferably, the feedback control unit includes an inter-phase SOC equalization control unit and an intra-phase SOC equalization control unit; and when the value of the health status recorded in the feature point called by the feedback control unit in real time deviates from the preset range, the parameters of the inter-phase SOC equalization control unit and the intra-phase SOC equalization control unit are adjusted to stabilize the output voltage of the feedback control unit.

[0016] A second aspect of the present invention relates to a cascaded energy storage SOC equalization control device utilizing the method of the first aspect of the present invention. The device is an energy storage converter device, including a feedback control unit. The feedback control unit is communicatively connected to the battery management system of the battery pack and extracts feature points through an estimation control table stored in the battery management system to achieve feedback control of the energy storage converter device.

[0017] The beneficial effects of this invention are that, compared with the prior art, the SOC equalization control method and device for cascaded energy storage in this invention can obtain the characteristic parameters of each cell in the battery pack by testing the battery pack, and fit the correlation between the battery's health state and charge / discharge voltage, thereby achieving real-time control of the battery pack's output state through this correlation. This invention is simple in method and ingenious in concept. By equalizing each cell, it improves the equalization speed and efficiency, reduces the constraints of energy storage systems on the consistency requirements of cascaded batteries, and improves the efficiency and capacity of integrated cascaded battery pack utilization.

[0018] The beneficial effects of the present invention also include:

[0019] 1. The device of this invention can adopt a modular design, which is easy to expand and maintain. At the same time, each cell can be independently controlled, which is beneficial for monitoring each cell and facilitating equalization control, thereby effectively improving the battery capacity and energy utilization rate.

[0020] 2. Employing a rapid health status assessment method based on State of Health (SOH) enables quick location of faulty batteries. Utilizing an independent control method with a multi-level controller enhances the fault immunity of the secondary battery system. This approach achieves online multi-level equalization control of the secondary battery system, significantly improving its cycle efficiency and lifespan. It can be widely adopted in future large-capacity secondary energy storage system integration projects.

[0021] 3. The rapid extraction method for the health status parameters of cascaded batteries in this invention can quickly extract the characteristic quantities of the health status of different types of cascaded batteries, thereby considering the battery balance control based on the health status, realizing the rapid and accurate location of faulty batteries, and improving the immunity of the system. Attached Figure Description

[0022] Figure 1This is a schematic diagram illustrating the steps of a cascaded energy storage SOC equalization control method according to the present invention.

[0023] Figure 2 This is a schematic diagram of the fitting curve for the 10 minutes before the end of charging in the SOC equalization control method of cascaded energy storage according to the present invention.

[0024] Figure 3 This is a schematic diagram of the fitting curve for the 5 minutes before the end of charging in the SOC equalization control method of cascaded energy storage according to the present invention.

[0025] Figure 4 This is a schematic diagram of the fitting curve for the SOC equalization control method of cascaded energy storage in the present invention, one minute before the end of charging.

[0026] Figure 5 This is a schematic diagram of the topology of the cascaded energy storage in the SOC equalization control method of the cascaded energy storage of the present invention.

[0027] Figure 6 This is a schematic diagram of the circuit structure of a single energy storage converter control unit in the SOC equalization control method of cascaded energy storage according to the present invention.

[0028] Figure 7 This is a schematic diagram of the circuit structure of the feedback control unit in the SOC equalization control method of cascaded energy storage according to the present invention.

[0029] Figure 8 This is a schematic diagram illustrating the principle of feedback control in the SOC equalization control method for cascaded energy storage according to the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this invention are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments not described in this invention obtained by those skilled in the art based on the embodiments described in this invention without creative effort should fall within the protection scope of this invention.

[0031] Figure 1 This is a schematic diagram illustrating the steps of a cascaded energy storage SOC equalization control method according to the present invention. Figure 1 As shown, the first aspect of the present invention relates to a SOC equalization control method for cascaded energy storage, the method comprising steps 1 to 3.

[0032] Step 1: Test the battery pack in the cascaded energy storage system in advance, extract the characteristic parameters of each cell in the battery pack, and construct a fitting function between the health state and charge / discharge voltage of each cell based on the characteristic parameters.

[0033] Understandably, because existing technologies only control the commutation output process of the battery pack through basic parameters such as output voltage and current, this leads to various problems in the output performance of the battery pack as described above. To address these issues, this invention improves upon the existing technology by using reliable indicators that fully characterize the battery pack's state and performance as an important reference for the converter in realizing the battery pack's circulating current process. Specifically, the reliable indicator selected in this invention is the State of Health (SOH) index of the individual cells.

[0034] In the prior art, there are various estimation algorithms for the state of health (SOH) of a battery. In order to make full use of the SOH indicator, this invention can use various methods in the prior art to obtain the specific value of the battery's state of health indicator.

[0035] Although there is a strong correlation between the health status of a battery and its basic characteristic parameters, the batteries used in the cascaded energy storage of this invention may come from various channels and brands, have different lifespans and conditions, and it is difficult to find batteries with consistent parameter characteristics that can be recycled in a tiered manner. Therefore, before calculating the basic condition indicators of the batteries, this invention adopts a pre-testing method to obtain the health status of each cell in the energy storage battery pack.

[0036] Preferably, the tests include battery capacity testing, hybrid power pulse capability testing, and low-rate battery charge-discharge testing.

[0037] The specific experimental steps for battery capacity testing are as follows:

[0038] (1) Charge the battery with constant current, set the charging current to 1 / 3C, which is 1 / 3 times the estimated battery capacity. Charge the battery and switch to constant voltage charging after the battery voltage reaches the upper limit of 3.65V. Stop charging when the charging current drops to 0.02C.

[0039] (2) The battery is left to stand for 1 hour.

[0040] (3) After the resting period, the battery is discharged under constant current. The discharge current is set to 1 / 3C until the battery voltage reaches the discharge cutoff voltage of 2.0V and the discharge is stopped to end the test.

[0041] (4) Let stand for 5 minutes to end the test.

[0042] Then, during the constant current discharge process of the battery, the discharge current and time are recorded to calculate the battery capacity parameters.

[0043] In addition, the internal resistance of the battery can be tested using the Hybrid Pulse Power Characteristic (HPPC) test method. Specifically, the test is carried out using the following steps:

[0044] (1) Charge the battery with constant current, set the charging current to 1 / 3C, and charge the battery. After the battery voltage reaches the upper limit of 3.65V, switch to constant voltage charging until the charging current drops to 0.02C and then stop charging.

[0045] (2) The battery is left to stand for 1 hour.

[0046] (3) Perform constant current discharge on the battery. Set the discharge current to 1 / 3C. If the battery voltage reaches 2.0V, stop the discharge and end the test. If it does not reach 2.0V, stop charging when the discharge time reaches 6 minutes and let it stand for 1 hour.

[0047] (4) Discharge the battery with a 1C current pulse for 10 seconds, let it rest for 40 seconds, then charge the battery with a 0.75C current pulse for 10 seconds, let it rest for 10 seconds. Return to step (3) until the battery reaches the battery discharge cutoff voltage and the test is completed.

[0048] (5) Let stand for 5 minutes to end the test.

[0049] During the testing process, the internal resistance of the battery can be obtained using the DC internal resistance calculation formula. When selecting testing points, the battery internal resistance can be measured at states of charge (SOC) of 90%, 80%, 70%, and so on, up to 10%. Since the discharge current uses a 1 / 3C rate, the battery SOC decreases by approximately 10% every 6 minutes of discharge. Therefore, the battery internal resistance is measured every 6 minutes to obtain the resistance at each testing point.

[0050] In addition, low-rate battery charge-discharge testing can also be used to obtain the battery's IC curve to obtain the voltage and current change characteristics during battery charge-discharge. The specific steps of low-rate battery charge-discharge testing are as follows:

[0051] (1) Charge the battery with constant current, set the charging current to 1 / 3C, and switch to constant voltage charging after the battery voltage reaches the upper limit of 3.65V. Stop charging when the charging current drops to 0.02C.

[0052] (2) The battery is left to stand for 1 hour.

[0053] (3) Perform constant current discharge on the battery, set the discharge current to 1 / 20C, stop discharging when the battery voltage reaches the lower limit voltage of 2.0V, and let the battery stand for 1 hour.

[0054] By using the above testing process, various parameters of the battery can be obtained, thus providing a basis for calculating the battery's health status.

[0055] Preferably, the characteristic parameters include charge / discharge voltage, battery capacity, battery charge level, battery internal resistance, remaining cycle count, battery temperature, and current rate. Based on these characteristic parameters, the health status of the cell unit is calculated.

[0056] It is understood that, through the above-described experimental process, or other measurement methods in the prior art, the relevant characteristic parameters of all cell units currently in operation in cascaded energy storage can be measured in this invention. The state of equilibrium (SOH) of the battery can then be calculated based on the aforementioned indicators.

[0057] There are various ways to convert the SOH of a battery in the prior art. The above method can be referred to in this invention. Alternatively, the index weight can be set according to the importance of each characteristic parameter to the SOH. The SOH value converted by each characteristic parameter is multiplied by the index weight, and then the sum is calculated to obtain the accurate SOH value.

[0058] In this invention, since each SOH value can correspond to the original value of each feature parameter, the fitting function between the charge / discharge voltage and the SOH value can be obtained based on this process.

[0059] Preferably, the fitting function is a linear fitting function; and, based on the charge and discharge duration of the unit battery, the fitting function of the unit battery under different charge and discharge durations is obtained respectively.

[0060] It is understood that in this invention, a fitting function can be constructed to determine the correspondence between SOH and charge / discharge voltage under different charge / discharge durations. Specifically, the charge / discharge voltage can be calculated by subtracting the initial voltage of the cell in its initial state from the actual voltage under the given charge / discharge duration, thereby obtaining the maximum operating voltage difference. Through this maximum operating voltage difference, the method of this invention can provide a more concrete understanding of the actual degree of change in charge / discharge voltage throughout the battery's operation.

[0061] In one embodiment of the present invention, the charging and discharging durations of 10 minutes, 5 minutes, and 1 minute before the end of charging were selected, respectively, to obtain the fitting curve. The present invention also supports using different time periods to characterize the correlation. Figure 2This is a schematic diagram of the fitting curve for the 10 minutes before the end of charging in the SOC equalization control method of cascaded energy storage according to the present invention. Figure 3 This is a schematic diagram of the fitting curve for the 5 minutes before the end of charging in the SOC equalization control method of cascaded energy storage according to the present invention. Figure 4 This is a schematic diagram of the fitting curve one minute before the end of charging in the SOC equalization control method of cascaded energy storage according to the present invention.

[0062] When charging reaches the last 10 minutes, the maximum operating voltage difference ΔU of the cell unit is... max Its fitting curve with SOH is as follows Figure 2 As shown, during the charging process, the charging terminal ΔU max It is linearly correlated with SOH: ΔU max = 0.3441 - 0.00369 × SOH, goodness of fit R 2 =0.9736. For example... Figure 3 As shown, during the charging process, the charging terminal ΔU max It is linearly correlated with SOH: ΔU max =0.4708 - 0.00453 × SOH, goodness of fit R² = 0.9684. For example... Figure 4 As shown, when charging reaches the last minute, the charging terminal ΔU during the charging process... max It is linearly correlated with SOH: ΔU max =0.4763-0.00275×SOH, goodness of fit R2=0.8964.

[0063] Using the method of this invention, the battery under test no longer needs to undergo usable capacity calibration to determine its SOH value. Instead, it only needs to calculate the maximum operating voltage difference ΔU of the battery cell module under test at that moment based on the charging end operating voltage data collected by the battery management system. max Then, the SOH value of the battery cell under test is found based on the fitted curve. Based on this method, the SOH of the battery pack in the modular cascaded energy storage system can be quickly and dynamically evaluated.

[0064] Step 2: Record the feature points in the fitted function in the estimation control table, and monitor the charging and discharging voltage of each cell in the battery pack in real time, so as to query the feature points in the estimation control table based on the charging and discharging voltage.

[0065] It should be noted that, in order to quickly and efficiently obtain battery health indicators using fitting functions to guide the instantaneous response of the converter, the multiple fitting functions mentioned above can be stored in a data table format. In this invention, this data table is called the estimation control table. By using the contents recorded in the estimation control table, the method of this invention can quickly obtain the battery health status by looking up data in the table and adjust the battery's commutation process accordingly.

[0066] Preferably, the estimation control table records the one-to-one correspondence between the cell number, charge / discharge duration, charge / discharge voltage, and health status. The feature points in the estimation control table are obtained based on the values ​​of the fitting function under uniformly distributed health status values.

[0067] It should be noted that since the states of individual cells in tiered utilization are not entirely consistent, the corresponding data can be retrieved based on the cell number. Alternatively, this invention can also set a unified approximate fitting curve for multiple cells in a single tier, allowing the tier to be determined based on the cell number, and the fitting data for that tier to be retrieved.

[0068] This invention can also select different fitting curves based on the actual charge and discharge duration of the battery. Furthermore, the current charge and discharge voltage of the battery is collected in real time by the energy storage monitoring unit in the battery management system, and a table is looked up to obtain the battery health corresponding to that voltage.

[0069] Step 3: Based on the feature points obtained from the query, acquire the health status of each cell in the battery pack, and adjust the feedback control unit of the cascaded energy storage to achieve stable output of the cascaded energy storage.

[0070] Preferably, the estimation control table is stored in the energy storage monitoring unit and is called in real time by the feedback control unit in the cascaded energy storage.

[0071] The feedback control unit in this invention is similar to the feedback control unit in existing converter equipment. Here, this invention first describes the specific contents of cascaded energy storage and its feedback control unit.

[0072] Figure 5 This is a schematic diagram of the topology of the cascaded energy storage system in the SOC equalization control method of the cascaded energy storage system of the present invention. Figure 5As shown, the cascaded energy storage converter system used in this invention is a direct-connected energy storage system, implemented using a cascaded H-bridge topology. Each power module contains an independent battery as an energy storage element, enabling bidirectional energy flow. Phases A, B, and C are connected in a Y- configuration. Each phase's AC output is connected to the power grid via a reactor. If a suitable margin is pre-set, the system possesses redundancy. In the event of a failure in a power module, the faulty link can be bypassed, thereby ensuring the normal and stable operation of the system.

[0073] Figure 6 This is a schematic diagram of the circuit structure of a single energy storage converter control unit in the SOC equalization control method of cascaded energy storage according to the present invention. Figure 6 As shown, in a single-link H-bridge power unit, the power unit consists of a single-phase full-bridge converter circuit, reactors, capacitors, pre-charge resistors, etc. The power unit has four-quadrant power operation capability, enabling the entire cascaded energy storage system to also achieve four-quadrant operation. The LC filter composed of reactors and capacitors performs filtering, reducing voltage and current fluctuations across the battery, which is beneficial for battery monitoring and extending battery life. In this embodiment of the invention, the functional unit topology also has an online bypass function. A bidirectional thyristor controls the bypass on / off state. In case of a unit failure, bypassing the power unit is achieved by providing a thyristor trigger pulse and a blocking switch drive signal.

[0074] Figure 7 This is a schematic diagram of the circuit structure of the feedback control unit in the SOC equalization control method for cascaded energy storage according to the present invention. Figure 7 As shown, the feedback control unit of a three-phase direct-connected energy storage converter can be divided into four main parts: grid-connected power decoupling control, inter-phase SOC equalization control, intra-phase SOC equalization control, and carrier phase-shifting pulse width modulation.

[0075] When the power grid is operating normally, the energy storage system receives a given active power p to be fed into the grid according to the grid dispatch instructions. * and reactive power q * The corresponding reference active power i to be injected into the grid is obtained through grid voltage vector orientation. d * and reactive current i q * Secondly, a feedforward decoupling control strategy is used to achieve decoupled control of active and reactive power, so that the system's output power meets the grid dispatch requirements.

[0076] Figure 8 This is a schematic diagram illustrating the principle of feedback control in the SOC equalization control method for cascaded energy storage according to the present invention. Figure 8As shown, the battery management system can sample and obtain the SOC values ​​of phases A, B, and C, as well as the average SOC value of the three phases, to perform inter-phase SOC balancing control. By changing the distribution of the three-phase output power, it achieves balanced management of the battery SOC among the three phases, thereby ensuring the consistency of the battery state among phases A, B, and C. Furthermore, by comparing the SOC state of each power unit battery cluster provided by the battery management system with the average SOC value of that phase, it is also possible to achieve SOC balancing control of the power unit battery cluster within a phase.

[0077] After superimposing the output signals of the above equalization control, the obtained reference modulation signal can be input to the pulse width modulation stage, thereby adjusting the on and off states of the switching transistors and completing the operation control of the energy storage converter.

[0078] Preferably, the feedback control unit includes an inter-phase SOC equalization control unit and an intra-phase SOC equalization control unit; and when the value of the health status recorded in the feature point called by the feedback control unit in real time deviates from the preset range, the parameters of the inter-phase SOC equalization control unit and the intra-phase SOC equalization control unit are adjusted to stabilize the output voltage of the feedback control unit.

[0079] It is understood that the method of the present invention can be specifically implemented by adjusting the balancing process of the inter-phase SOC balancing control unit and the intra-phase SOC balancing control unit. For example, when a deviation of the health status value is detected from a preset range, the output voltage ratio allocated to the battery by the inter-phase SOC balancing control unit or the intra-phase SOC balancing control unit can be modified accordingly. Alternatively, when multiple batteries are found to have deviated health status values, the voltage range output by the feedback control unit can be adjusted as a whole by adjusting the relevant parameters in the inter-phase SOC balancing control unit or the intra-phase SOC balancing control unit, or the parameters of other parts of the feedback control unit.

[0080] In summary, this invention can obtain an accurate battery health status by monitoring the battery's output voltage, current and other basic parameters in real time, thereby achieving balanced adjustment of SOC based on the battery health status and accurate prediction of the battery's future performance.

[0081] A second aspect of the present invention relates to a cascaded energy storage SOC equalization control device utilizing the method of the first aspect of the present invention. The device is an energy storage converter device, including a feedback control unit. The feedback control unit is communicatively connected to the battery management system of the battery pack and extracts feature points through an estimation control table stored in the battery management system to achieve feedback control of the energy storage converter device.

[0082] It is understood that the cascaded energy storage SOC balancing control device includes hardware structures and / or software modules corresponding to the execution of each function in order to achieve the various functions provided in the embodiments of this application. Those skilled in the art should readily recognize that, based on the algorithm steps of the examples described in conjunction with the embodiments disclosed herein, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware 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.

[0083] This application embodiment can divide the equalization control device into functional modules according to the above method example. For example, each function can be divided into its own functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. It should be noted that the module division in this application embodiment is illustrative and only represents one logical functional division. In actual implementation, there may be other division methods.

[0084] The device includes at least one processor, a bus system, and at least one communication interface. The processor may be a central processing unit (CPU), or it may be replaced by a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or other hardware, or the FPGA or other hardware may work together with the CPU as a processor.

[0085] The memory can be read-only memory (ROM) or other types of static storage devices capable of storing static information and instructions, random access memory (RAM) or other types of dynamic storage devices capable of storing information and instructions, or electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed discs, laser discs, optical discs, universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited to these. The memory can exist independently and be connected to the processor via a bus. The memory can also be integrated with the processor.

[0086] The hard drive can be a mechanical hard drive or a solid-state drive (SSD), etc. The interface card can be a host bus adapter (HBA), a redundant array of independent disks (RID), an expander card, or a network interface controller (NIC), etc., and this embodiment of the invention is not limited to any particular type. The interface card in the hard drive module communicates with the hard drive. The storage node communicates with the interface card of the hard drive module to access the hard drive in the hard drive module.

[0087] The hard drive interface can be Serial Attached Small Computer System Interface (SAS), Serial Advanced Technology Attachment (SATA), or Peripheral Component Interconnect Express (PCIe), etc.

[0088] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented using software programs, implementation can be, in whole or in part, in the form of a computer program product. This computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device containing one or more servers, data centers, etc., that can be integrated with the medium. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state disks (SSDs)).

[0089] The computer program instructions used to perform the operations of this invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing state information from the computer-readable program instructions. This electronic circuitry can execute the computer-readable program instructions to implement various aspects of the invention.

[0090] The beneficial effects of this invention are that, compared with the prior art, the SOC equalization control method and device for cascaded energy storage in this invention can obtain the characteristic parameters of each cell in the battery pack by testing the battery pack, and fit the correlation between the battery's health state and charge / discharge voltage, thereby achieving real-time control of the battery pack's output state through this correlation. This invention is simple in method and ingenious in concept. By equalizing each cell, it improves the equalization speed and efficiency, reduces the constraints of energy storage systems on the consistency requirements of cascaded batteries, and improves the efficiency and capacity of integrated cascaded battery pack utilization.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A SOC equalization control method for cascaded energy storage, characterized in that, The method includes the following steps: Step 1: Test the battery pack in the cascaded energy storage system in advance and extract the characteristic parameters of each cell in the battery pack. The characteristic parameters include the charge and discharge voltage. Based on the characteristic parameters, calculate the health status of the cell and construct a fitting function between the health status of each cell and the charge and discharge voltage. The charge and discharge voltage is the maximum working voltage difference calculated by subtracting the initial voltage of the cell in the initial state from the actual voltage under the charge and discharge time. Step 2: Record the feature points in the fitting function in the estimation control table, and monitor the charging and discharging voltage of each cell in the battery pack in real time, so as to query the feature points in the estimation control table based on the charging and discharging voltage. The feature points in the estimation control table are obtained according to the value of the fitting function under the uniformly distributed values ​​of the health state. Step 3: Based on the feature points obtained from the query, obtain the health status of each cell in the battery pack, and adjust the feedback control unit of the cascaded energy storage to achieve stable output of the cascaded energy storage. The estimation control table is stored in the energy storage monitoring unit and is called in real time by the feedback control unit in the cascaded energy storage.

2. The SOC equalization control method for cascaded energy storage according to claim 1, characterized in that: The tests include battery capacity testing, hybrid power pulse capability testing, and low-rate battery charge / discharge testing.

3. The SOC equalization control method for cascaded energy storage according to claim 2, characterized in that: The characteristic parameters also include battery capacity, battery charge, battery internal resistance, remaining cycle count, battery temperature, and current rate.

4. The SOC equalization control method for cascaded energy storage according to claim 3, characterized in that: The fitting function is a linear fitting function; and... Based on the charge and discharge duration of the unit battery, the fitting function of the unit battery under different charge and discharge durations is obtained.

5. The SOC equalization control method for cascaded energy storage according to claim 4, characterized in that: The estimation control table is used to record the one-to-one correspondence between the unit battery number, the charging and discharging duration, the charging and discharging voltage, and the health status.

6. The SOC equalization control method for cascaded energy storage according to claim 5, characterized in that: The feedback control unit includes an inter-phase SOC equalization control unit and an intra-phase SOC equalization control unit; and... When the value of the health status recorded in the feature point called by the feedback control unit in real time deviates from the preset range, the parameters of the inter-phase SOC equalization control unit and the intra-phase SOC equalization control unit are adjusted to stabilize the output voltage of the feedback control unit.

7. A cascaded energy storage SOC equalization control device utilizing the method described in any one of claims 1-6, characterized in that: The device is an energy storage converter device, which includes a feedback control unit; Furthermore, the feedback control unit is communicatively connected to the battery management system of the battery pack, and extracts feature points through the estimation control table stored in the battery management system to achieve feedback control of the energy storage converter device.

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