Battery electric quantity detection method and energy storage system

Abstract

The invention discloses a battery electric quantity detection method and an energy storage system, and the method comprises the steps: determining a first voltage of an energy storage battery, the first voltage being a battery end voltage when the energy storage battery executes the electric energy conversion of a first working condition, and the first working condition being charging or discharging of the energy storage battery; determining at least one first state of charge estimation value according to the first voltage, each first state of charge estimation value being obtained by performing state of charge estimation on an energy storage battery by using a corresponding state of charge estimation mode, a state-of-charge estimation mode adopted by the energy storage battery for state-of-charge estimation is associated with the battery end voltage of the energy storage battery; and according to the at least one first state-of-charge estimation value, determining a second state-of-charge estimation value of the energy storage battery. According to the scheme, the problem of inaccuracy caused by a single state-of-charge estimation mode can be solved, and the precision and reliability of state-of-charge estimation are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy, and particularly to a method for detecting battery power and an energy storage system. Background Art

[0002] The popularization of energy storage systems (such as household energy storage and grid-level energy storage) in the new energy field has made the estimation of the state of charge (SOC) of batteries a core issue. The SOC estimation is not only used to guide the charging and discharging operations of batteries to achieve optimal utilization of energy, but also can effectively avoid overcharging or over-discharging of batteries, thereby ensuring the performance and service life of batteries.

[0003] Common SOC estimation methods mainly include Coulomb counting method, static OCV calibration method, model prediction method, and data-driven method. Common SOC estimation methods are usually used for estimating the battery power of SOC in the fields of mobile phones and electric vehicles. However, the SOC calculation in the energy storage field is different from that in the fields of mobile phones and electric vehicles. Especially in the energy storage field, the computing resources and energy consumption are strictly limited, making it difficult to apply some complex calculation methods that are feasible in the fields of mobile phones and electric vehicles. Moreover, the energy storage field faces more extreme situations, such as drastic changes in temperature, which may cause significant fluctuations in battery performance and affect the accuracy of SOC calculation. At the same time, the charging and discharging fluctuations of energy storage systems are extremely drastic. Especially, the power generation of photovoltaic power generation is greatly affected by the light intensity and cannot be accurately predicted, and the fluctuations of household power loads are also unpredictable. The frequent start and stop of household electrical appliances will cause a sharp change in the load current. These complex and uncontrollable charging and discharging fluctuations pose higher requirements for the real-time performance and accuracy of SOC calculation in the energy storage field. In contrast, the charging and discharging of mobile phones and electric vehicles are relatively stable and relatively predictable. Therefore, the methods for estimating the battery power of SOC in the fields of mobile phones and electric vehicles are difficult to meet the requirements of SOC calculation in the energy storage field. Summary of the Invention

[0004] The present invention provides a method for detecting battery power and an energy storage system. By dynamically determining the battery terminal voltage of an energy storage battery in real time to determine the state-of-charge estimation method that needs to participate in the state-of-charge estimation, it is realized that multiple state-of-charge estimation methods are fused at an appropriate time for state-of-charge estimation, so as to solve the inaccurate problem caused by relying solely on a single state-of-charge estimation method, and significantly improve the accuracy and reliability of state-of-charge estimation.

[0005] According to one aspect of the present invention, a method for detecting battery power is provided. The method includes:

[0006] Determine a first voltage of the energy storage battery, where the first voltage is the battery terminal voltage when the energy storage battery performs the power conversion of a first working condition, and the first working condition is that the energy storage battery is charged or discharged;

[0007] Determine at least one first state of charge (SOC) estimate based on the first voltage. Each of the first SOC estimates is obtained by estimating the SOC of the energy storage battery using a corresponding SOC estimation method, and the SOC estimation method used for the SOC estimation of the energy storage battery is associated with the battery terminal voltage of the energy storage battery.

[0008] Determine a second SOC estimate of the energy storage battery based on the at least one first SOC estimate.

[0009] According to another aspect of the present invention, there is provided an energy storage system, including: at least one battery module; at least one battery management system, where the at least one battery management system corresponds to the at least one battery module one by one, the battery management system is electrically connected to the corresponding battery module, and the battery management system is used to execute the battery power detection method according to any embodiment of the present invention.

[0010] The technical solution of the embodiment of the present invention establishes an association between the battery terminal voltage of the energy storage battery and the SOC estimation method. Under the working conditions of charging or discharging the energy storage battery, at least one suitable SOC estimation method can be dynamically and accurately selected based on the battery terminal voltage of the energy storage battery, changing the limitation of previously fixedly using a single SOC estimation method, fully considering the battery characteristic differences of the energy storage battery in different voltage states, obtaining at least one first SOC estimate obtained based on different SOC estimation methods, using different SOC estimation methods to evaluate the SOC from different angles, reducing the error that may be generated by a single method. On this basis, by fusing multiple first SOC estimates, the advantages of each first SOC estimate in the SOC estimation process are effectively integrated, greatly improving the accuracy of the SOC estimation of the energy storage battery.

[0011] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0013] Figure 1 It is a flowchart of a battery power detection method provided according to an embodiment of the present invention.

[0014] Figure 2 It is a flowchart of another method for detecting battery power according to an embodiment of the present invention;

[0015] Figure 3 It is a schematic diagram of a curve of battery terminal voltage based on temperature - current rate applicable to an embodiment of the present invention;

[0016] Figure 4 It is a flowchart of yet another method for detecting battery power according to an embodiment of the present invention;

[0017] Figure 5 It is a flowchart of the fusion of state - of - charge estimation methods in battery power detection according to an embodiment of the present invention. Detailed implementation manners

[0018] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above - mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "include" and "have" and any variations thereof are intended to cover non - exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily need to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0020] Figure 1 An embodiment of the present invention provides a flowchart of a method for detecting battery power. This embodiment is applicable to the situation of estimating the state of charge of an energy storage battery in a charging or discharging condition. This method can be configured in an energy storage system, which can be implemented in the form of hardware and / or software, and the energy storage system can be configured in any electronic device with network communication functions.

[0021] As Figure 1 shown, the method for detecting battery power in this embodiment includes the following processes:

[0022] S110. Determine the first voltage of the energy storage battery. The first voltage is the battery terminal voltage when the energy storage battery performs power conversion under the first operating condition, and the first operating condition is charging or discharging of the energy storage battery.

[0023] The energy storage battery may refer to a battery that converts chemical energy into electrical energy and has an energy storage function. The energy storage battery can convert electrical energy into chemical energy and store it in the battery during charging, and can convert the stored chemical energy back into electrical energy and release it when discharging is required. The energy storage battery can be applied to various fields such as various electronic devices, electric vehicles, renewable energy power generation systems, etc., to achieve effective storage and utilization of electrical energy. The energy storage battery may include, but is not limited to, the following types of batteries: lead-acid batteries, lithium-ion batteries, flow batteries, sodium-sulfur batteries, nickel-cadmium batteries, and nickel-metal hydride batteries.

[0024] The first voltage is obtained by measuring the potential difference between the positive and negative terminals of the energy storage battery when the energy storage battery performs power conversion under the first operating condition. In one example, a voltage measuring instrument configured in the energy storage system is used to connect the positive and negative measuring terminals of the voltage measuring instrument to the positive and negative terminals of the energy storage battery, and the voltage value displayed by the measuring instrument is directly read to obtain the first voltage of the energy storage battery. In another example, the battery management system (BMS) in the energy storage system is used to directly obtain the first voltage of the energy storage battery. The battery management system (BMS) integrates a voltage sensor, which can real-time monitor the battery terminal voltage of the energy storage battery and transmit the data to the control unit of the energy storage system, so as to obtain the first voltage of the energy storage battery. Among them, the energy storage system can be household energy storage or grid-level energy storage.

[0025] In an optional example, the first operating condition may be charging of the energy storage battery. The power conversion performed in the charging state is to input electrical energy to the energy storage battery, and the energy storage battery converts the electrical energy into chemical energy and stores it. The battery terminal voltage of the energy storage battery will gradually increase during the charging process, and the charging current varies according to the charging strategy and battery characteristics.

[0026] In another optional example, the first operating condition may be discharging of the energy storage battery. The power conversion performed in the discharging state is to convert the chemical energy stored in the energy storage battery into electrical energy and release it to supply power to an external load. The battery terminal voltage of the energy storage battery gradually decreases during the discharging process, and the magnitude of the discharging current depends on the power of the load and the discharging ability of the battery.

[0027] S120. Determine at least one first state of charge estimate value according to the first voltage. Each first state of charge estimate value is obtained by estimating the state of charge of the energy storage battery using a corresponding state of charge estimation method. The state of charge estimation method used for the state of charge estimation of the energy storage battery is related to the battery terminal voltage of the energy storage battery.

[0028] The State of Charge (SOC) can refer to the ratio of the electric charge stored in an energy storage battery under certain conditions to the total electric charge when the energy storage battery is fully charged, usually expressed as a percentage. The State of Charge is used to measure the remaining electric charge of the energy storage battery, reflecting the electric charge state of the energy storage battery during the entire charge and discharge cycle, guiding the charge and discharge operations of the energy storage battery, optimizing energy use, and avoiding overcharging or over-discharging of the energy storage battery. For example, when the SOC of an energy storage battery is 80%, it means that the current electric charge of the energy storage battery is 80% of its full charge capacity.

[0029] As a key indicator, the State of Charge SOC enables the Battery Management System (BMS) to monitor the electric charge state of the energy storage battery in real time. Once the SOC approaches the thresholds of overcharging or over-discharging, the Battery Management System (BMS) will take corresponding measures, such as cutting off the charging circuit to prevent overcharging and limiting the discharge current to prevent over-discharging, thereby effectively protecting the battery, ensuring its safe and stable operation, extending the battery's service life, avoiding safety issues such as overheating, bulging, or even fire and explosion that may be caused by overcharging, and preventing irreversible internal chemical reactions in the battery and reducing the battery capacity due to over-discharging.

[0030] In related solutions, a single State of Charge estimation method is fixedly used to estimate the State of Charge of the energy storage battery. For example, the ampere-hour integration estimation method or the open-circuit voltage method is used to estimate the State of Charge of the energy storage battery. Through the ampere-hour integration estimation method, the SOC of the energy storage battery can be continuously updated and calculated based on the current data measured in real time during the charge and discharge process of the battery, thereby timely reflecting the change of the battery's electric charge. However, the charge and discharge efficiency of the battery is not constant but is affected by various factors, such as battery temperature, charge and discharge rate, battery aging degree, etc. Using a single fixed State of Charge estimation method is okay under some specific conditions, but there will be problems of inaccurate State of Charge estimation under other conditions.

[0031] Therefore, several State of Charge estimation methods can be configured for the State of Charge estimation of the energy storage battery to match a suitable State of Charge estimation method for the energy storage battery. Moreover, considering that the battery terminal voltage is an external manifestation of the internal chemical state of the battery, during the charge and discharge process of the battery, the internal chemical reactions of the battery will cause changes in the chemical composition and ion concentration of the electrode material, etc. These changes will directly affect the battery terminal voltage. It can be seen that there is a certain regular relationship between the battery terminal voltage and the State of Charge. Therefore, the battery terminal voltage of the energy storage battery can be used to determine the State of Charge estimation method to be used when estimating the State of Charge of the energy storage battery.

[0032] The first voltage is the battery terminal voltage when the energy storage battery performs power conversion under the first operating condition. The state-of-charge (SOC) estimation method to be selected for the energy storage battery depends on the magnitude of the battery terminal voltage of the energy storage battery. Therefore, at least one SOC estimation method that the energy storage battery needs to adopt under the first voltage can be selected according to the first voltage. Using different SOC estimation methods to estimate the SOC of the energy storage battery at the first voltage can obtain respective corresponding first SOC estimation values, and since different SOC estimation methods may be based on different principles and algorithms, there will be differences in the obtained first SOC estimation values.

[0033] The battery terminal voltage of the energy storage battery is an external manifestation of the internal chemical state of the battery. Especially as the battery charge-discharge process progresses, the chemical reactions inside the battery will cause changes in the chemical composition of the electrode material and ion concentration, etc. These changes will directly affect the terminal voltage of the battery. It can be seen that by identifying the battery terminal voltage of the energy storage battery, information about the battery SOC can be obtained. Different SOCs correspond to different terminal voltage ranges. For example, in a lead-acid battery, when the battery is approaching full charge, the battery terminal voltage will gradually increase and stabilize at a relatively high value; while when the battery power is low, the battery terminal voltage will drop to a relatively low level. Therefore, selecting an SOC estimation method that matches the battery terminal voltage according to the battery terminal voltage of the energy storage battery can more accurately reflect the actual SOC of the energy storage battery.

[0034] S130. Determine a second SOC estimation value of the energy storage battery according to at least one first SOC estimation value.

[0035] Optionally, determining a second SOC estimation value of the energy storage battery according to at least one first SOC estimation value includes: adding at least one first SOC estimation value and then taking the average to obtain the second SOC estimation value of the energy storage battery. The second SOC estimation value reflects the SOC of the energy storage battery at the first voltage.

[0036] Optionally, determining a second SOC estimation value of the energy storage battery according to at least one first SOC estimation value includes: performing weighted averaging on each first SOC estimation value in at least one first SOC estimation value according to the weight of each first SOC estimation value in at least one first SOC estimation value to obtain the second SOC estimation value of the energy storage battery. The second SOC estimation value reflects the SOC of the energy storage battery at the first voltage.

[0037] Optionally, several state-of-charge estimation methods provided for the energy storage battery may include a first type of state-of-charge estimation method, a second type of state-of-charge estimation method, and a third type of state-of-charge estimation method. Among them, the first type of state-of-charge estimation method is a method of estimating the state of charge using ampere-hour integration; the second type of state-of-charge estimation method is a method of estimating the state of charge by using the mapping relationship between the battery terminal voltage and the state of charge for the charge-discharge efficiency error caused by the change of the battery characteristics of the energy storage battery; the third type of state-of-charge estimation method is a method of estimating the state of charge by interpolation compensation using the state of charge of the energy storage battery at different battery terminal voltages obtained in advance.

[0038] A single state-of-charge estimation method may have limitations. Affected by battery characteristic changes, environmental factor interference, etc., the state-of-charge estimation result may not be accurate enough. By adopting multiple state-of-charge estimation methods related to the battery terminal voltage, the state of charge of the battery can be estimated from different angles, and then by synthesizing these state-of-charge estimation values, the error of a single state-of-charge estimation method can be reduced, and the accuracy and reliability of the state-of-charge estimation can be improved.

[0039] Under different usage scenarios and working conditions, the performance and characteristics of the energy storage battery will be different. For example, under different conditions such as temperature and charge-discharge rate, the voltage-state-of-charge relationship of the battery may change. Introducing multiple state-of-charge estimation methods can better adapt to these changes because different state-of-charge estimation methods may have different adaptabilities to different working conditions of the energy storage battery. By selecting a suitable state-of-charge estimation method or combining multiple state-of-charge estimation methods according to the battery terminal voltage of the energy storage battery, the state of charge of the energy storage battery under various working conditions can be estimated more accurately, thereby better managing the energy storage battery.

[0040] Moreover, in practical applications, the battery management system in the energy storage system may face various uncertainties and interferences, such as sensor errors, internal battery faults, etc. Adopting multiple state-of-charge estimation methods can increase the redundancy and robustness of the system. Even if one estimation method is interfered with or fails, other estimation methods can still provide relatively reliable state-of-charge estimation values, ensuring that the energy storage system can continue to operate normally, avoiding misjudgment of the battery state due to the failure of a single estimation method, and improving the stability and safety of the entire energy storage system.

[0041] In the technical solution of the embodiment of the present invention, by establishing an association between the battery terminal voltage of the energy storage battery and the state-of-charge estimation method, in the working conditions of charging or discharging the energy storage battery, at least one suitable state-of-charge estimation method can be dynamically and accurately selected according to the battery terminal voltage of the energy storage battery, changing the limitation of fixedly using a single state-of-charge estimation method in the past, fully considering the battery characteristic differences of the energy storage battery in different voltage states, obtaining at least one first state-of-charge estimation value obtained based on different state-of-charge estimation methods, using different state-of-charge estimation methods to evaluate the state of charge from different angles, reducing the error that may be generated by a single method. On this basis, by fusing multiple first state-of-charge estimation values, the advantages of each first state-of-charge estimation value in the state-of-charge estimation process are effectively integrated, and the accuracy of the state-of-charge estimation of the energy storage battery is greatly improved.

[0042] Figure 2 FIG. is a schematic flow chart of another method for detecting the battery power provided by the embodiment of the present invention. The technical solution of this embodiment further optimizes the process of determining at least one first state-of-charge estimation value according to the first voltage in the foregoing embodiment on the basis of the technical solution of the foregoing embodiment. This embodiment can be combined with each optional solution in the foregoing one or more embodiments.

[0043] As Figure 2 shown, the method for detecting the battery power of this embodiment may include the following processes:

[0044] S210. Determine the first voltage of the energy storage battery. The first voltage is the battery terminal voltage when the energy storage battery performs the power conversion of the first working condition, and the first working condition is charging or discharging the energy storage battery.

[0045] S220. Determine at least one first state-of-charge estimation method associated with the first voltage from several first state-of-charge estimation methods. The first voltage is used to identify the power conversion stage in which the energy storage battery is located when performing the power conversion of the first working condition, and there are differences in the state-of-charge estimation methods applicable to the energy storage battery in different power conversion stages.

[0046] The power conversion process of the energy storage battery performing the first working condition can be divided into multiple power conversion stages and gradually completed. That is, in the case of the energy storage battery performing the power conversion of the first working condition, the power conversion process of the first working condition is decomposed into a series of interrelated sub-processes, and each sub-process constitutes a power conversion stage. The energy storage battery can sequentially go through different power conversion stages in a certain order to realize the power conversion process under the first working condition.

[0047] Since energy storage batteries have different characteristics in different power conversion stages (such as changes in parameters like current, voltage, internal resistance, etc.), it is very difficult for a single state of charge (SOC) estimation method to maintain a high-precision SOC estimation in all power conversion stages. Therefore, when an energy storage battery performs power conversion in different power conversion stages, there are certain differences in the SOC estimation methods applicable to the SOC estimation of the energy storage battery. Thus, selecting a suitable SOC estimation method for the energy storage battery according to the characteristics of different power conversion stages can more accurately estimate the SOC of the energy storage battery. Selecting a suitable SOC estimation method or combination according to different power conversion stages can give full play to the advantages of various methods and improve the accuracy and reliability of SOC estimation.

[0048] A number of first SOC estimation methods are multiple different SOC estimation methods pre-configured for the energy storage battery. Since the first voltage can be used to identify the specific power conversion stage in which the energy storage battery is located during the power conversion process related to the first working condition, and there are differences in the SOC estimation methods applicable to the energy storage battery in different power conversions, the first voltage can be used to select at least one first SOC estimation method that is suitable for the energy storage battery at the first voltage from among the numerous first SOC estimation methods.

[0049] As an optional but non-limiting implementation manner, determining at least one first SOC estimation method associated with the first voltage from among a number of first SOC estimation methods includes, but is not limited to, the following steps A1 - A3:

[0050] Step A1: Determine the second voltage and the third voltage of the energy storage battery. The second voltage and the third voltage form a number of voltage intervals as voltage critical values for dividing the different power conversion stages experienced by the energy storage battery during the power conversion of the first working condition.

[0051] Step A2: Determine at least one first SOC estimation method from among a number of first SOC estimation methods according to the first voltage, the second voltage, and the third voltage.

[0052] Optionally, the second voltage and the third voltage can be two voltages pre-configured according to the change in the battery characteristics of the energy storage battery during the power conversion process of the first working condition. When the first working condition is to charge the energy storage battery, the second voltage is less than the third voltage; when the first working condition is to discharge the energy storage battery, the second voltage is greater than the third voltage.

[0053] Optionally, the second voltage is the reference voltage among the respective reference battery terminal voltages; each reference battery terminal voltage is the battery terminal voltage that is the same as the voltage determined by mapping the temperature and current rate of the energy storage battery at the first voltage among the respective battery terminal voltages recorded corresponding to each state of charge correction point; different states of charge and the mutual mapping relationship between each state of charge and at least one battery terminal voltage are recorded corresponding to each state of charge correction point; the third voltage is used to characterize the battery terminal voltage at the start of the end stage of the first operating condition of the energy storage battery.

[0054] There is a good mapping relationship between the end voltage of charge and discharge of the energy storage battery and the state of charge (SOC). Therefore, it can be used for SOC calibration during this period. For the energy storage battery, a series of voltage-SOC mapping points can be established under charge and discharge operating conditions, and these mapping points are defined as the state of charge correction points pre-configured for the energy storage battery. For each state of charge correction point, a state of charge and the mutual mapping relationship between each state of charge and at least one battery terminal voltage are recorded corresponding to each state of charge correction point. Through these state of charge correction points, the corresponding relationship between the state of charge and the battery terminal voltage can be established.

[0055] Each of the reference battery terminal voltages can be the battery terminal voltage selected from the respective battery terminal voltages recorded corresponding to different state of charge correction points, and each reference battery terminal voltage is the same as the voltage determined by mapping the temperature and current rate of the energy storage battery at the first voltage recorded by the state of charge correction point to which the reference battery terminal voltage belongs.

[0056] Among the numerous battery terminal voltages recorded at each state of charge correction point, according to the temperature and current rate of the energy storage battery at the first voltage, the battery terminal voltages that are the same as it are found through the mapping relationship based on each state of charge correction point. These same battery terminal voltages constitute the set of reference battery terminal voltages, and a reference voltage determined from this set is the second voltage.

[0057] Optionally, when the first operating condition is the charging condition of the energy storage battery, the reference voltage satisfies at least one of the following: the reference voltage is the minimum voltage among the respective reference battery terminal voltages; the reference voltage is not greater than the first voltage, and the difference between the first voltage and the reference voltage is less than the difference between the first voltage and the reference battery terminal voltages other than the reference voltage among the respective reference battery terminal voltages.

[0058] Optionally, when the first operating condition is the discharging condition of the energy storage battery, the reference voltage satisfies at least one of the following: the reference voltage is the maximum voltage among the respective reference battery terminal voltages; the reference voltage is not less than the first voltage, and the difference between the first voltage and the reference voltage is less than the difference between the first voltage and the reference battery terminal voltages other than the reference voltage among the respective reference battery terminal voltages.

[0059] The second voltage is a specific voltage value, serving as a voltage threshold to define the start or end of an electric energy conversion stage during the electric energy conversion process of the energy storage battery under the first operating condition. Similarly, the third voltage is similar to the second voltage and is also a battery terminal voltage threshold, which can also be used to divide an electric energy conversion stage during the electric energy conversion process of the energy storage battery under the first operating condition, representing the start or end of another electric energy conversion stage. The first voltage is different from the second voltage, and the first voltage is less than the second voltage. Therefore, by using the second voltage and the third voltage as the battery terminal voltage thresholds, the electric energy conversion process of the energy storage battery under the first operating condition being executed can be divided into different electric energy conversion stages. Subsequently, by judging the voltage magnitude relationship between the first voltage, the second voltage, and the third voltage, the specific electric energy conversion stage of the energy storage battery at the first voltage can be determined. Among them, the first voltage can be denoted as Vcurrent, the second voltage as Vdc1, and the third voltage as Vchgstart.

[0060] Based on the first voltage, in combination with the second voltage and the third voltage, at least one first state of charge estimation method suitable for the current state of the energy storage battery is selected from several first state of charge estimation methods. Here, the second voltage and the third voltage serve as battery terminal voltage thresholds to divide different electric energy conversion stages during the electric energy conversion of the energy storage battery when executing the first operating condition. By judging the voltage magnitude relationship between the first voltage, the second voltage, and the third voltage, the specific electric energy conversion stage of the energy storage battery at the first voltage can be determined, thereby screening out at least one first state of charge estimation method associated with the first voltage from several first state of charge estimation methods.

[0061] As an optional but non-limiting implementation manner, at least one first state of charge estimation method is determined from several first state of charge estimation methods according to the first voltage, the second voltage, and the third voltage, including but not limited to the following steps B11 - B13:

[0062] Step B11: When the first voltage is within the first voltage range, determine the first type of state of charge estimation method among several first state of charge estimation methods as the at least one first state of charge estimation method. The first type of state of charge estimation method is the method of estimating the state of charge using ampere-hour integration.

[0063] Step B12: When the first voltage is within the second voltage range, determine at least one first state-of-charge estimation method from among several first state-of-charge estimation methods, including the first type of state-of-charge estimation method and the second type of state-of-charge estimation method. The second type of state-of-charge estimation method is a method for estimating the state of charge by using the mapping relationship between the battery terminal voltage and the state of charge of the energy storage battery to compensate for the charge-discharge efficiency error caused by changes in the battery characteristics of the energy storage battery.

[0064] Step B13: When the first voltage is within the third voltage range, determine at least one first state-of-charge estimation method from among several first state-of-charge estimation methods, including the first type of state-of-charge estimation method, the second type of state-of-charge estimation method, and the third type of state-of-charge estimation method. The third type of state-of-charge estimation method is a method for estimating the state of charge by interpolation compensation using the pre-acquired state of charge of the energy storage battery at different battery terminal voltages.

[0065] Among them, the second type of state-of-charge estimation method is used to compensate for the cumulative error in the state-of-charge estimation caused by the first type of state-of-charge estimation method due to the charge-discharge efficiency error caused by changes in the battery characteristics of the energy storage battery. The third type of state-of-charge estimation method is used to suppress the state-of-charge jump of the energy storage battery after the end stage of the first working condition due to the calibration error of the mapping relationship between the battery terminal voltage and the state of charge of the energy storage battery.

[0066] Among them, the first voltage range, the second voltage range, and the third voltage range correspond in sequence to several voltage ranges formed by the second voltage and the third voltage as voltage critical values. When the first working condition is the charging condition of the energy storage battery, the first voltage range is the range where the voltage is less than the second voltage, the second voltage range is the range where the voltage is not less than the second voltage and less than the third voltage, and the third voltage range is the range where the voltage is not less than the third voltage. When the first working condition is the discharging condition of the energy storage battery, the first voltage range is the range where the voltage is greater than the second voltage, the second voltage range is the range where the voltage is not greater than the second voltage and greater than the third voltage, and the third voltage range is the range where the voltage is not greater than the third voltage.

[0067] During the charge and discharge process of the battery, there are several key stages with different characteristics, which play an important role in accurately estimating the state of charge (SOC) of the battery.

[0068] The power conversion stage where the first voltage is within the first voltage range belongs to the stage in the battery charge and discharge process where the voltage remains basically constant. During this period, since the voltage hardly changes, it is impossible to correct the SOC by means of the conventional correspondence between voltage and SOC. At this time, the ampere-hour integration method is used to estimate the SOC of the energy storage battery. In the power conversion stage where the first voltage is within the first voltage range, the chemical reaction inside the battery is relatively stable, resulting in extremely weak changes in its terminal voltage. Traditional means of calibrating SOC based on voltage changes are difficult to play a role. The ampere-hour integration method can effectively track the change of the battery charge by integrating the charge and discharge current over time.

[0069] In the power conversion stage where the first voltage is within the second voltage range, the voltage of the energy storage battery will change significantly, and at this time, there is a good correspondence between the voltage and the SOC. Based on this characteristic, when estimating the SOC, it is necessary to gradually reduce the weight ratio of the ampere-hour integration in the calculation process, and at the same time, correspondingly increase the proportion of the result obtained by dynamic correction (based on voltage changes) in the SOC estimation. Through this precise correspondence between voltage and SOC, the SOC can be corrected and estimated more accurately, thereby improving the accuracy of SOC estimation.

[0070] In the power conversion stage where the first voltage is within the third voltage range, when the energy storage battery is approaching the fully charged or discharged state, it enters the end stage of charge and discharge. In this stage, if only the dynamic correction method is used to calibrate the SOC, it is not necessarily possible to ensure complete accuracy, and there may be a deviation of 3% to 5% in actual applications. In order to effectively avoid the situation where the SOC jumps when the battery reaches the fully charged or discharged state, the priority of interpolation correction is set to the highest at this time. Specifically, when the battery voltage reaches the preset fully charged or discharged voltage value, through the interpolation correction method, it can be ensured that the SOC is exactly corrected to 100% or 0%. In this process, the weights of the ampere-hour integration and the dynamic correction result in the SOC estimation will be gradually reduced. This is because in the end stage of charge and discharge, the electrochemical process inside the battery becomes complex, and the ampere-hour integration may be affected by various factors and generate errors. The dynamic correction also decreases in accuracy because the battery is approaching the limit state. The interpolation correction can comprehensively consider various factors and finely adjust the SOC through a specific algorithm, thereby effectively ensuring the stability and accuracy of the SOC estimation when the battery is fully charged or discharged.

[0071] By considering multiple voltage parameters (the first voltage, the second voltage, and the third voltage) and the relationships between multiple voltages and different electric energy conversion stages, the electric energy conversion stage in which the energy storage battery is located can be identified, so as to select a more appropriate state-of-charge estimation method. Compared with only using a single parameter or a simple estimation method, this method based on multi-parameters and stage division can more accurately reflect the actual state of charge of the battery, reduce the estimation error, and this method can adapt to different first operating conditions and the changes of the energy storage battery under different working conditions. Since the influences of factors such as temperature and current rate on the battery terminal voltage are considered, and the electric energy conversion stages are divided according to different voltage critical values, the state-of-charge estimation method can be dynamically adjusted according to the actual situation.

[0072] As an optional but non-limiting implementation manner, at least one first state-of-charge estimation method is determined from several first state-of-charge estimation methods according to the first voltage, the second voltage, and the third voltage, including but not limited to the following steps B21 - B23:

[0073] Step B21, when it is determined according to the first voltage that the energy storage battery is in the first electric energy conversion stage, the state-of-charge estimation method of the first type in several first state-of-charge estimation methods is determined as at least one first state-of-charge estimation method, and the state-of-charge estimation method of the first type is a method of estimating the state of charge by ampere-hour integration.

[0074] Step B22, when it is determined according to the first voltage that the energy storage battery is in the second electric energy conversion stage, the state-of-charge estimation method of the first type and the state-of-charge estimation method of the second type in several first state-of-charge estimation methods are determined as at least one first state-of-charge estimation method, and the state-of-charge estimation method of the second type is a method of estimating the state of charge by using the mapping relationship between the battery terminal voltage and the state of charge of the energy storage battery for the charge-discharge efficiency error caused by the change of the battery characteristics of the energy storage battery.

[0075] Step B23, when it is determined according to the first voltage that the energy storage battery is in the third electric energy conversion stage, the state-of-charge estimation method of the first type, the state-of-charge estimation method of the second type, and the state-of-charge estimation method of the third type in several first state-of-charge estimation methods are determined as at least one first state-of-charge estimation method, and the state-of-charge estimation method of the third type is a method of estimating the state of charge by interpolation compensation by using the state of charge of the energy storage battery obtained in advance at different battery terminal voltages.

[0076] Among them, the second type of state of charge (SOC) estimation method is used to compensate for the cumulative error of the SOC estimation of the first type of SOC estimation method caused by the charge-discharge efficiency error due to the change in the battery characteristics of the energy storage battery; the third type of SOC estimation method is used to suppress the SOC jump of the energy storage battery after the end stage of the first working condition caused by the calibration error of the mapping relationship between the battery terminal voltage and the SOC of the energy storage battery.

[0077] Among them, when charging the energy storage battery in the first working condition, the first power conversion stage is the stage where the battery terminal voltage of the energy storage battery is less than the second voltage, the second power conversion stage is the stage where the battery terminal voltage of the energy storage battery is not less than the second voltage and less than the third voltage, and the third power conversion stage is the stage where the battery terminal voltage of the energy storage battery is not less than the third voltage. When discharging the energy storage battery in the first working condition, the first power conversion stage is the stage where the battery terminal voltage of the energy storage battery is greater than the second voltage, the second power conversion stage is the stage where the battery terminal voltage of the energy storage battery is not greater than the second voltage and greater than the third voltage, and the third power conversion stage is the stage where the battery terminal voltage of the energy storage battery is not greater than the third voltage.

[0078] In the actual application of the SOC algorithm, there are significant scenario differences between the energy storage field and mobile phones and electric vehicles. From the perspective of computing resources, energy storage products are essentially different from mobile phones and electric vehicles. Compared with mobile phones and electric vehicles, the computing resources of energy storage products are extremely limited, their chip computing power is low, and considering the energy consumption problem, energy storage products do not interact with the cloud platform (i.e., the background data management system) frequently. This means that large models and complex algorithms suitable for mobile phones and electric vehicles are difficult to implement in the energy storage field and do not meet the requirements of the energy storage system for efficient algorithms to meet the SOC calculation accuracy. From the charge-discharge scenario, the differences between energy storage products and mobile phones and electric vehicles are also obvious. When mobile phones and electric vehicles are charging, they rely on a stable power grid for power supply, and the charging working condition is relatively certain, making the SOC calibration during the charging process relatively easy. However, energy storage products prefer to use the PV (photovoltaic charging) method. Due to the continuous change of sunlight intensity, the charging current may not only fluctuate violently but also often have a very small current charging situation, greatly increasing the difficulty of SOC calibration. In the discharge scenario, the random connection and disconnection of household loads lead to frequent fluctuations in the discharge current of energy storage products, further increasing the complexity of SOC calibration.

[0079] Furthermore, the influence of temperature conditions on the SOC algorithm cannot be ignored. The usage scenarios of mobile phones are mostly in indoor environments with stable temperatures, or the temperature is kept suitable because they are placed in warm clothes. Electric vehicles are equipped with a perfect thermal management system, which can effectively maintain the stability of the operating temperature. In sharp contrast, energy storage systems are usually installed outdoors. Considering energy consumption issues, the energy storage system will not actively heat up under non-essential circumstances (such as forced charging at low battery power or low SOC); and due to the product sealing requirements, there is generally no air duct for heat dissipation, which causes the temperature of the battery cells to fluctuate greatly during the operation of the energy storage system, and the impact on the SOC estimation of energy storage batteries is more obvious.

[0080] In addition, for energy storage points, the differences in the types of battery cells of energy storage batteries also affect the application of the SOC algorithm. Usually, mobile phones and electric vehicles mostly use NCM (ternary lithium) battery cells, while energy storage products generally use LFP (lithium iron phosphate) battery cells considering the combination of price and safety. Compared with NCM battery cells, LFP battery cells have the significant feature of a longer third power conversion stage of the working voltage. During the third power conversion stage, the charge and discharge voltage changes very little, which makes it impossible to achieve full-range SOC calibration like NCM battery cells, and the impact on the SOC estimation of energy storage batteries is also relatively serious.

[0081] To address these special needs in the energy storage field, this solution innovatively proposes a SOC algorithm with low computational complexity. Through the technical solution of steps B11-B13 and / or steps B21-B23, the specific SOC estimation method to be used for the energy storage battery when estimating the SOC can be accurately determined based on the real-time voltage of the energy storage battery. This allows the most suitable SOC estimation method to be flexibly selected at different power conversion stages of the energy storage battery, effectively achieving a delicate balance between SOC calculation complexity and accuracy. Specifically, by integrating the estimated values obtained from multiple SOC estimation methods, the algorithm has extremely low computational complexity in terms of limited computing resources and energy consumption, enabling smooth operation even when the computing power of the energy storage product chip is insufficient, without the need for powerful computing resources. At the same time, it avoids the high energy consumption caused by frequent data exchange with the cloud platform or running complex algorithms, greatly improving the energy utilization efficiency of the energy storage system and reducing long-term operating costs. Given the current situation of many extreme conditions in the energy storage field, this algorithm can reduce the inaccurate SOC estimation caused by extreme temperature conditions of the energy storage battery. In addition, in extreme conditions such as internal short circuits and aging of electrode materials that may occur in the battery, the estimated values obtained by integrating multiple state of charge estimation methods can effectively avoid SOC misjudgments due to internal battery failures; and in the face of the challenge of drastic charging and discharging fluctuations, it can capture the rapid changes in charging current in real time, and use its efficient data processing capabilities to quickly adjust the SOC calculation method to avoid SOC calculation errors caused by weak current. To address the problem of large fluctuations in household electricity loads, it ensures that the SOC estimate can still accurately reflect the battery's true state of charge when the load changes frequently.

[0082] S230: Estimating the state of charge of the energy storage battery according to at least one first state of charge estimation method to obtain at least one first state of charge estimation value.

[0083] Each first state of charge estimation value is obtained by estimating the state of charge of the energy storage battery using a corresponding state of charge estimation method, and the state of charge estimation method used for estimating the state of charge of the energy storage battery is associated with the battery terminal voltage of the energy storage battery.

[0084] Each first state of charge estimation method may refer to a specific calculation logic that can estimate the state of charge of an energy storage battery based on the characteristics and operating data of the energy storage battery (such as voltage, current, temperature, etc.) using specific algorithms and models. Different first state of charge estimation methods can estimate the state of charge of the energy storage battery based on different physical principles, mathematical models, or algorithms. For example, the ampere-hour integration method, open-circuit voltage method, Kalman filtering method, neural network method, etc. can all be specific implementation forms of the first state of charge estimation method. The above-mentioned first type of state of charge estimation method, second type of state of charge estimation method, and third type of state of charge estimation method can also be specific implementation forms of the first state of charge estimation method.

[0085] As an optional but non-limiting implementation manner, according to at least one first state of charge estimation method, performing state of charge estimation on the energy storage battery to obtain at least one first state of charge estimation value, including but not limited to the following steps C11 - C13:

[0086] Step C11: When at least one first state of charge estimation method includes a second type of state of charge estimation method, determining the respective reference battery terminal voltages recorded corresponding to a plurality of state of charge correction points, each reference battery terminal voltage being the same as the voltage determined by mapping based on the temperature and current rate of the energy storage battery at the first voltage, and each state of charge correction point corresponding to a recorded mutual mapping relationship between the state of charge and at least one battery terminal voltage; wherein, the second type of state of charge estimation method is a method for estimating the state of charge by using the mapping relationship between the battery terminal voltage and the state of charge of the energy storage battery for the charge and discharge efficiency error caused by the change of the battery characteristics of the energy storage battery.

[0087] Step C12: Comparing each reference battery terminal voltage with the first voltage in the order of the respective reference battery terminal voltages, and determining the target battery terminal voltage triggered by the first voltage from the respective reference battery terminal voltages, the voltage difference between the target battery terminal voltage and the first voltage being less than the voltage differences between the first voltage and the remaining reference battery terminal voltages other than the target battery terminal voltage among the respective reference battery terminal voltages.

[0088] Step C13: Determining the first state of charge estimation value when performing state of charge estimation on the energy storage battery according to the state of charge associated with the target battery terminal voltage.

[0089] The target battery terminal voltage is the voltage among the respective reference battery terminal voltages that is closest to the first voltage, that is, the voltage difference between the target battery terminal voltage and the first voltage is less than the voltage differences between the other reference battery terminal voltages and the first voltage. When the first operating condition is to charge the energy storage battery, the target battery terminal voltage is less than or equal to the first voltage; when the first operating condition is to discharge the energy storage battery, the target battery terminal voltage is greater than or equal to the first voltage.

[0090] In the order of the respective reference battery terminal voltages, compare each reference battery terminal voltage with the first voltage actually measured for the energy storage battery. By comparing the differences between each reference battery terminal voltage and the first voltage, find the reference battery terminal voltage with the smallest difference from the first voltage as the target battery terminal voltage. Considering that when the first operating condition is to charge the energy storage battery, as the charging progresses, the battery terminal voltage continuously increases until it stabilizes. Therefore, determine the reference battery terminal voltage that the first voltage just starts to be greater than or equal to among the respective reference battery terminal voltages as the target battery terminal voltage; while, when the first operating condition is to discharge the energy storage battery, as the discharging progresses, the battery terminal voltage continuously decreases. Therefore, a reference battery terminal voltage that the first voltage just starts to be less than or equal to among the respective reference battery terminal voltages can be determined as the target battery terminal voltage, so as to find the battery terminal voltage value that can best represent the actual state of the current battery among many reference battery terminal voltages, in order to estimate the state of charge of the energy storage battery based on the state of charge associated with the target battery terminal voltage.

[0091] Based on the state of charge associated with the target battery terminal voltage, determine the first state-of-charge estimation value when estimating the state of charge of the energy storage battery. Since the target battery terminal voltage is the reference voltage closest to the first voltage, the state of charge associated with the target battery terminal voltage can better reflect the actual state of charge of the energy storage battery at the first voltage, thus providing a basis for the accurate estimation of the state of charge.

[0092] See Figure 3, the dynamic compensation gain estimation SOC (defined as SOC2) is performed through the third type of state of charge estimation method. At the end of the charge and discharge of the energy storage battery, there is a good mapping relationship between the battery terminal voltage and the state of charge SOC. At this time, it can be used for SOC calibration. Its voltage is defined as the reference battery terminal voltage corresponding to the state of charge correction trigger, that is, it is considered that after the battery terminal voltage reaches the reference battery terminal voltage corresponding to the state of charge correction trigger, the SOC reaches the SOC mapped by the reference battery terminal voltage corresponding to the state of charge correction trigger. A series of battery terminal voltage-state of charge SOC mapping points are pre-established during the charge and discharge of the energy storage battery, which are defined as state of charge correction points. Assume that the charging process of the energy storage battery is pre-configured with n state of charge correction points (SOCdc1, Vdc1), (SOCdc2, Vdc2)...(SOCdc1, Vdcn), and the discharging process of the energy storage battery is pre-configured with m state of charge correction points (SOCdc1, Vdc1), (SOCdc2, Vdc2)...(SOCdc1, Vdcm), where SOCdc is defined as the state of charge correction SOC, and Vdc is defined as the reference battery terminal voltage corresponding to the state of charge correction trigger. Vdci in each mapping point is a two-dimensional table of temperature-current rate, and this two-dimensional table is calibrated by charge and discharge test data. For example, for a state of charge correction point SOCdci, the graph of its corresponding voltage Vdci.

[0093] See Figure 3 , to determine whether there is a state of charge correction point that is triggered among each state of charge correction point, the two-dimensional table of battery terminal voltage [temperature, current rate] to be queried can be determined first through the mapping relationship (SOCdci, Vdci), and then the reference battery terminal voltage Vdci corresponding to the state of charge correction trigger can be obtained by looking up the two-dimensional table of battery terminal voltage [temperature, current rate]. Finally, by comparing the relationship between the first voltage and the reference battery terminal voltage corresponding to the state of charge correction trigger, it is judged whether there is a state of charge correction point that is triggered. The discrete relationship between the reference battery terminal voltage Vdci corresponding to the trigger of each state of charge correction point and the temperature and current of the energy storage battery. To improve the dynamic correction accuracy, data fitting is performed on this two-dimensional table, and the battery terminal voltage model corresponding to the state of charge correction trigger is established as follows:

[0094] Vdci(T,C) = a0 + b1 + a1*T + b1*C + a2*T^2 + b2*C^2... + a2*T^n + b2*C^n

[0095] Among them, T is the temperature of the energy storage battery, C is the current rate of the energy storage battery, n is the order of the battery terminal voltage model corresponding to the state of charge correction trigger, and the model order can be adjusted according to requirements. To avoid overfitting and too high model complexity, it is restricted that n ≤ 5.

[0096] By considering the effects of the temperature, current rate, and changes in battery characteristics of the energy storage battery on the charge-discharge efficiency error, and using the mapping relationship between the battery terminal voltage and the state of charge recorded at the state of charge correction point, the state of charge of the energy storage battery can be estimated more comprehensively and accurately. Especially in the case of changes in battery characteristics, such as battery aging, different ambient temperatures, etc., this method can effectively compensate for the estimation error caused by the characteristic changes and improve the accuracy of the estimation result. Moreover, this solution can dynamically determine the reference battery terminal voltage and the target battery terminal voltage according to the actual working conditions (temperature, current rate, etc.) of the battery, so as to adapt to different working environments and working condition changes, and make the state of charge estimation maintain good stability and reliability in various complex application scenarios.

[0097] As an optional but non-limiting implementation manner, according to at least one first state of charge estimation method, the state of charge of the energy storage battery is estimated to obtain at least one first state of charge estimation value, including but not limited to the following steps C21 - C23:

[0098] Step C21, when at least one first state of charge estimation method includes a third type of state of charge estimation method, determine the third voltage and the fourth voltage of the energy storage battery. The third voltage is the battery terminal voltage at the beginning of the end stage of the first working condition of the energy storage battery, and the fourth voltage is the battery terminal voltage limit reached when the energy storage battery continuously performs the power conversion related to the first working condition in the end stage of the first working condition. Among them, the third type of state of charge estimation method is a method of estimating the state of charge by interpolation compensation using the pre-acquired state of charge of the energy storage battery at different battery terminal voltages.

[0099] Step C22, determine the third state of charge estimation value and the fourth state of charge estimation value of the energy storage battery. The third state of charge estimation value is the state of charge estimation value obtained by using the first type of state of charge estimation method when the energy storage battery is at the third voltage, and the fourth state of charge estimation value is the state of charge estimation value when the energy storage battery is at the fourth voltage. Among them, the first type of state of charge estimation method is a method of estimating the state of charge by ampere-hour integration.

[0100] Step C23, according to the first voltage, the third voltage, the fourth voltage, the third state of charge estimation value, and the fourth state of charge estimation value, determine the first state of charge estimation value when the energy storage battery performs the state of charge estimation.

[0101] Estimation of SOC by ampere-hour integration (defined as SOC1): SOC1(k + 1) = SOC1(k) + η * Isamp * Δt / Qmax. Where SOC1(k + 1) is the ampere-hour integration SOC at the current moment, SOC1(k) is the ampere-hour integration SOC at the previous moment, η is the Coulomb efficiency, obtained through experimental tests, with a value range of 0.99 < η < 1, Isamp is the sampled current at the current moment, Δt is the single-step sampling time, and Qmax is the maximum capacity of the current battery state.

[0102] Interpolative compensation estimation of SOC (defined as SOC3) is performed through the third type of state of charge estimation method. The charging condition of the energy storage battery is as follows:

[0103] SOC3 = SOCchgstart + (Vchgcurrent - Vchgstart) * (SOCchgLmt - SOCchgstart) / (VchgLmt - Vchgstart);

[0104] Where, SOCchgstart is the state of charge SOC corresponding to the battery terminal voltage at the beginning of the end stage of charging of the energy storage battery, SOCchgLmt is the upper limit of the state of charge SOC corresponding to the upper limit value of the battery terminal voltage that can be continuously charged in the end stage of charging of the energy storage battery, Vchgstart is the battery terminal voltage at the beginning of the end stage of charging of the energy storage battery, VchgLmt is the upper limit value of the battery terminal voltage that can be continuously charged in the end stage of charging of the energy storage battery, and Vchgcurrent is the first voltage detected in real time during the charging stage of the energy storage battery.

[0105] The discharging condition of the energy storage battery is as follows:

[0106] SOC3 = (Vdsgcurrent - VdsgLmt) * (SOCdsgstart - SOCdsgLmt) / (Vdsgstart - VdsgLmt);

[0107] Where, SOCdsgstart is the state of charge SOC corresponding to the battery terminal voltage at the beginning of the end stage of discharging of the energy storage battery, SOCdsgLmt is the lower limit of the state of charge SOC corresponding to the lower limit value of the battery terminal voltage that can be continuously charged in the end stage of discharging of the energy storage battery, Vdsgstart is the battery terminal voltage at the beginning of the end stage of discharging of the energy storage battery, VdsgLmt is the lower limit value of the battery terminal voltage that can be continuously discharged in the end stage of discharging of the energy storage battery, and Vdsgcurrent is the first voltage detected in real time during the discharging stage of the energy storage battery.

[0108] Among them, the single change of the state of charge (SOC) is restricted not to exceed ΔSOC, that is, it is necessary to satisfy SOC3(k + 1)>SOC3(k)+ΔSOC. When the change amount between the estimated SOC values estimated by the third type of SOC estimation method at two adjacent moments does not exceed the preset SOC change amount ΔSOC, then SOC3(k + 1)=SOC3(k)+ΔSOC. SOC3(k + 1) is the SOC estimated by the third type of SOC estimation method at the current moment, and SOC3(k) is the SOC estimated by the third type of SOC estimation method at the previous moment.

[0109] Among them, the single change of SOC3 is restricted from regressing. That is to say, when the first working condition is the charging condition of the energy storage battery, it is necessary to satisfy SOC3(k + 1)<SOC3(k), otherwise configure SOC3(k + 1)=SOC3(k); when the first working condition is the discharging condition of the energy storage battery, it is necessary to satisfy SOC3(k + 1)>SOC3(k), otherwise configure SOC3(k + 1)=SOC3(k).

[0110] 240. Determine the second state of charge estimate value of the energy storage battery according to at least one first state of charge estimate value.

[0111] The technical solution of the embodiment of the present invention can not only achieve the technical effects of the foregoing embodiments, but also takes into account the different characteristics of the energy storage battery in different electric energy conversion stages. For example, in the initial and final stages of charging, the voltage and current change laws of the battery are different. Using the first state of charge estimation method associated with the first voltage and suitable for the electric energy conversion stage can fully consider the characteristics of the energy storage battery in different electric energy conversion stages, so as to more accurately estimate the state of charge of the battery. Moreover, by adopting different state of charge estimation methods for different electric energy conversion stages, more refined management can be carried out according to the actual situation of the battery in each stage. Accurate state of charge estimation helps to prevent the battery from overcharging, over-discharging and working in an inappropriate state. That is to say, by using a suitable estimation method in different electric energy conversion stages, the charge and discharge process of the battery can be better controlled, the damage to the battery can be reduced, thereby prolonging the service life of the battery and reducing the operating cost of the energy storage system.

[0112] Figure 4 It is a schematic flowchart of another method for detecting the battery power provided by the embodiment of the present invention. The technical solution of this embodiment further optimizes the process of determining the second state of charge estimate value of the energy storage battery according to at least one first state of charge estimate value in the foregoing embodiment on the basis of the technical solution of the foregoing embodiment. This embodiment can be combined with each optional solution in the above one or more embodiments.

[0113] Such as Figure 4As shown, the method for detecting the battery power of this embodiment may include the following processes:

[0114] S510. Determine the first voltage of the energy storage battery. The first voltage is the battery terminal voltage when the energy storage battery performs power conversion under the first working condition, and the first working condition is charging or discharging of the energy storage battery.

[0115] S520. Determine at least one first state of charge estimation method associated with the first voltage from several first state of charge estimation methods. The power conversion process of the first working condition performed by the energy storage battery is divided into multiple power conversion stages and gradually completed. The first voltage is used to identify the power conversion stage in which the energy storage battery is located when performing power conversion under the first working condition. There are differences in the state of charge estimation methods configured for use by the energy storage battery in different power conversion stages.

[0116] S530. Estimate the state of charge of the energy storage battery according to at least one first state of charge estimation method to obtain at least one first state of charge estimation value.

[0117] Wherein, each first state of charge estimation value is obtained by estimating the state of charge of the energy storage battery using a corresponding state of charge estimation method. The state of charge estimation method used for estimating the state of charge of the energy storage battery is associated with the battery terminal voltage of the energy storage battery.

[0118] S540. Determine the weight of each first state of charge estimation value among at least one first state of charge estimation value. The weight of each first state of charge estimation value depends on the weight of the first state of charge estimation method corresponding to the first state of charge estimation value. The weight of each first state of charge estimation method is related to the first voltage of the energy storage battery.

[0119] Each first state of charge estimation value is a specific value obtained by estimating the state of charge of the energy storage battery through a corresponding first state of charge estimation method. Since the battery characteristic differences of the energy storage battery in different voltage states are fully considered, one or more first state of charge estimation methods are used when estimating the state of charge of the energy storage battery. Therefore, there are multiple first state of charge estimation values, and each first state of charge estimation value estimates the state of charge of the energy storage battery from different perspectives or based on different principles.

[0120] Each weight of the first state of charge (SOC) estimation value represents the importance degree of each first SOC estimation value or the first SOC estimation method in the entire estimation system. The greater the weight of each first SOC estimation value, the greater the influence of the first SOC estimation value or the first SOC estimation method on the final result. That is to say, due to factors such as their principles, accuracies, and applicable ranges, different estimation methods have different importance degrees in the entire estimation process, and this importance degree is reflected by the weights. When the first voltage energy storage battery performs power conversion under the first working condition, the battery terminal voltage changes continuously with the first voltage during the entire SOC estimation process. The energy storage battery will correspond to different battery states, thereby affecting each first SOC estimation method used by the energy storage battery and the weights of each first SOC estimation method.

[0121] As an optional but non-limiting implementation manner, determining the weight of each first SOC estimation value in the at least one first SOC estimation value includes, but is not limited to, the following steps E1 - E2:

[0122] Step E1: Determine the first weight information and the second weight information associated with the first voltage of the energy storage battery. The first weight information is used to indicate the weights of each first SOC estimation method configured corresponding to the start of the power conversion stage when the energy storage battery is at the first voltage, and the second weight information is used to indicate the weights of each first SOC estimation method configured corresponding to the end of the power conversion stage when the energy storage battery is at the first voltage.

[0123] Step E2: Determine the weight of each first SOC estimation value in the at least one first SOC estimation value according to the first voltage and the first weight information and the second weight information associated with the first voltage.

[0124] The first weight information is weight description data related to the first SOC estimation method, and is used to determine the relative importance of each first SOC estimation method for the SOC estimation of the energy storage battery at the start of the power conversion stage when the energy storage battery is at the first voltage. Through the first weight information, the contribution degree of each first SOC estimation method to the SOC estimation result at the start of the power conversion stage when the energy storage battery is at the first voltage can be determined.

[0125] The second weight information is similar to the first weight information. It is the weight of each first SOC estimation method for the situation at the end of the power conversion stage when the energy storage battery is at the first voltage, and reflects the contribution degree of each first SOC estimation method to the SOC estimation result at the end of the power conversion stage when the energy storage battery is at the first voltage.

[0126] The weights of the first state-of-charge estimation methods indicated by the first weight information and the weights of the first state-of-charge estimation methods indicated by the second weight information can form the upper and lower limits of the weights of the first state-of-charge estimation methods within the power conversion stage when the energy storage battery is at the first voltage. The upper and lower limits of the weights of each first state-of-charge estimation method indicated by the first weight information and the second weight information can be combined, and the weights of each first state-of-charge estimation value can be allocated between the upper and lower limits of the weights of each first state-of-charge estimation method in combination with the first voltage, where the sum of the weights of each first state-of-charge estimation value is a preset value.

[0127] To determine the weight of each first state-of-charge estimation value based on the first weight information and the second weight information, and to comprehensively consider the process of the weights of the two power conversion stages, according to the progress of the power conversion stage, a suitable weight for each first state-of-charge estimation value can be determined by means of some interpolation or weighted average method in combination with the first weight information and the second weight information. For example, if currently at the middle position of the power conversion stage, the weights of each first state-of-charge estimation value can be calculated according to the first weight information and the second weight information in a linear interpolation manner, so that the weights of the first state-of-charge estimation values can be reasonably adjusted as the power conversion stage changes.

[0128] Taking into account the weight changes of different estimation methods at the start and end of the power conversion stage, the weights can be allocated more precisely according to the characteristics of the battery at different stages. Compared with only using fixed weights or single-stage weights, this method can better adapt to the dynamic changes of the battery during the entire power processing process, thus assigning more realistic weights to each estimation value and improving the accuracy of the state-of-charge estimation. As the power conversion stage progresses, by combining the first weight information and the second weight information to adjust the weights of the estimation values, the state-of-charge estimation system can flexibly adjust the importance of different estimation methods in real time according to the stage and state of the battery, so that it can better cope with various complex changes during the charging and discharging process of the battery. Through more reasonable weight allocation, the advantages of different estimation methods at different stages can be fully utilized, and each estimation value can be combined more optimally.

[0129] When the first voltage is within the first voltage range, at least one of the first state-of-charge estimation methods only includes the first type of state-of-charge estimation method. The weight of the first type of state-of-charge estimation method is configured as the weight of the first type of state-of-charge estimation method indicated by the first weight information associated with the first voltage. The first weight information associated with the first voltage is the same as the second weight information, and the weight of the first type of state-of-charge estimation method indicated is a preset value, and the preset value is 1.

[0130] When the first voltage is in the second voltage range, at least one first state of charge estimation method includes a first type of state of charge estimation method and a second type of state of charge estimation method. Based on the weights of the state of charge estimation methods of each type indicated by the first weight information associated with the first voltage, the weight of the first type of state of charge estimation method is adjusted negatively with the change of the first voltage, and the weight of the second type of state of charge estimation method is adjusted positively with the change of the first voltage;

[0131] When the first voltage is in the third voltage range, at least one first state of charge estimation method includes a first type of state of charge estimation method, a second type of state of charge estimation method, and a third type of state of charge estimation method. Based on the weights of the state of charge estimation methods of each type indicated by the first weight information associated with the first voltage, the weight of the first type of state of charge estimation method is adjusted negatively with the change of the first voltage, the weight of the second type of state of charge estimation method is adjusted negatively with the change of the first voltage, and the weight of the third type of state of charge estimation method is adjusted positively with the change of the first voltage;

[0132] Wherein, when the first working condition is the working condition of charging the energy storage battery, the first voltage range is the range where the voltage is less than the second voltage, the second voltage range is the range where the voltage is not less than the second voltage and less than the third voltage, and the third voltage range is the range where the voltage is not less than the third voltage; when the first working condition is the working condition of discharging the energy storage battery, the first voltage range is the range where the voltage is greater than the second voltage, the second voltage range is the range where the voltage is not greater than the second voltage and greater than the third voltage, and the third voltage range is the range where the voltage is not greater than the third voltage; the first type of state of charge estimation method is the method of estimating the state of charge by ampere-hour integration; the second type of state of charge estimation method is the method of estimating the state of charge by using the mapping relationship between the battery terminal voltage and the state of charge of the energy storage battery for the charge-discharge efficiency error caused by the change of the battery characteristics of the energy storage battery; the third type of state of charge estimation method is the method of estimating the state of charge by interpolation compensation using the pre-acquired state of charge of the energy storage battery at different battery terminal voltages.

[0133] As an optional but non-limiting implementation manner, determining the weight of each first state of charge estimation value in at least one first state of charge estimation value according to the first voltage and the first weight information and the second weight information associated with the first voltage includes, but is not limited to, the following steps D1-D4:

[0134] Step D1: Determine the weight difference associated with the first voltage based on the first weight information and the second weight information associated with the first voltage. The weight difference associated with the first voltage is the difference between the weights of each first state-of-charge estimation method indicated by the first weight information and the second weight information associated with the first voltage.

[0135] Step D2: Determine the voltage difference associated with the first voltage based on the first voltage and the fifth voltage. The voltage difference associated with the first voltage is represented by the absolute value of the difference between the first voltage and the fifth voltage. The fifth voltage is the starting voltage of the reference voltage range among several voltage ranges formed with the second voltage and the third voltage as voltage thresholds, and the first voltage is within the reference voltage range.

[0136] Step D3: Determine the weight adjustment amount for each first state-of-charge estimation method associated with the first voltage based on the voltage difference associated with the first voltage and the weight difference associated with the first voltage.

[0137] Step D4: Adjust the first weight information associated with the first voltage according to the weight adjustment amount for each first state-of-charge estimation method associated with the first voltage to obtain the weight of each first state-of-charge estimation value among at least one first state-of-charge estimation value.

[0138] Optionally, when the reference voltage range is the second voltage range, the starting voltage of the reference voltage range is the second voltage, and the ending voltage of the reference voltage range is the third voltage; when the reference voltage range is the third voltage range, the starting voltage of the reference voltage range is the third voltage, and the ending voltage of the reference voltage range is the fourth voltage. The fourth voltage is the battery terminal voltage limit reached when the energy storage battery continuously performs the power conversion related to the first operating condition in the final stage of the first operating condition. When the first operating condition is the charging condition of the energy storage battery, the fourth voltage is the upper limit of the battery terminal voltage reached when the energy storage battery continuously charges in the final stage of charging; when the first operating condition is the discharging condition of the energy storage battery, the fourth voltage is the lower limit of the battery terminal voltage reached when the energy storage battery continuously discharges in the final stage of discharging.

[0139] Among them, when the first operating condition is the charging condition of the energy storage battery, the first voltage range is the range where the voltage is less than the second voltage, the second voltage range is the range where the voltage is not less than the second voltage and less than the third voltage, and the third voltage range is the range where the voltage is not less than the third voltage; when the first operating condition is the discharging condition of the energy storage battery, the first voltage range is the range where the voltage is greater than the second voltage, the second voltage range is the range where the voltage is not greater than the second voltage and greater than the third voltage, and the third voltage range is the range where the voltage is not greater than the third voltage.

[0140] Optionally, the weight adjustment amount of each first state of charge estimation method associated with the first voltage is determined based on the ratio of the first value to the second value. The first value is the product result of the voltage difference associated with the first voltage and the weight difference associated with the first voltage, and the second value is the absolute value of the voltage difference between the starting voltage and the ending voltage of the reference voltage where the first voltage is located.

[0141] Exemplarily, refer to Figure 5 , when the first working condition is the charging condition of the energy storage battery, the second voltage is recorded as Vdc1, the third voltage is recorded as Vchgstart, the fourth voltage is recorded as VchgLmt, and the first voltage is Vcurrent. When the first working condition is the charging condition of the energy storage battery, the first voltage range is the range where the voltage is less than the second voltage, the second voltage range is the range where the voltage is not less than the second voltage and less than the third voltage, and the third voltage range is the range where the voltage is not less than the third voltage. Then, the charging is divided into the following three stages:

[0142] First power conversion stage: When the first voltage is in the first voltage range, it is necessary to satisfy Vcurrent < Vdc1;

[0143] Second power conversion stage: When the first voltage is in the second voltage range, it is necessary to satisfy Vdc1 <= Vcurrent < Vchgstart;

[0144] Third power conversion stage: When the first voltage is in the third voltage range, it is necessary to satisfy Vchgstart <= Vcrrent < VchgLmt.

[0145] Exemplarily, when the first working condition is the discharging condition of the energy storage battery, the second voltage is recorded as Vdc1, the third voltage is recorded as Vchgstart, the fourth voltage is recorded as VchgLmt, and the first voltage is Vcurrent. When the first working condition is the discharging condition of the energy storage battery, the first voltage range is the range where the voltage is greater than the second voltage, the second voltage range is the range where the voltage is not greater than the second voltage and greater than the third voltage, and the third voltage range is the range where the voltage is not greater than the third voltage. Similarly, the discharging is divided into the following three stages:

[0146] First power conversion stage: When the first voltage is in the first voltage range, it is necessary to satisfy Vcurrent > Vdc1;

[0147] Second power conversion stage: When the first voltage is in the second voltage range, it is necessary to satisfy Vdc1 >= Vcurrent > Vchgstart;

[0148] Third power conversion stage: When the first voltage is in the third voltage range, it is necessary to satisfy Vchgstart >= Vcrrent > VchgLmt.

[0149] The weights of the three state of charge (SOC) estimation methods are denoted as x, y, and z respectively, and the sum of the three is 1. That is, the algorithm for estimating the state of charge by strategy fusion is as follows:

[0150] SOC = x * SOC1 + y * SOC2 + z * SOC3;

[0151] x + y + z = 1;

[0152] Among them, SOC1, SOC2, and SOC3 are the state of charge estimation values obtained by using the first type of state of charge estimation method, the second type of state of charge estimation method, and the third type of state of charge estimation method respectively. x, y, and z are the weights of the first type of state of charge estimation method, the second type of state of charge estimation method, and the third type of state of charge estimation method respectively.

[0153] In the first power conversion stage, only the SOC1 estimation takes effect. The first weight information corresponding to the start of the first power conversion stage is fixed as x = 1, y = 0, z = 0. For the convenience of description, the second weight configuration corresponding to the end of the first power conversion stage is recorded as x1 = 1, y1 = 0, z1 = 0.

[0154] In the second power conversion stage, only the SOC1 and SOC2 estimations take effect. The first weight value information at the start of the second power conversion stage satisfies x + y = 1; z = 0; Using the second weight information at the end of the first power conversion stage as the first weight information at the start of the second power conversion stage, the second weight information at the end of the second power conversion stage is defined as x2, y2, z2. During this period, as the voltage rises, x gradually decreases and y gradually increases. The x weight adjustment amount during the second power conversion stage is defined as Δx, and its calculation formula is as follows:

[0155] Δx = (Vcurrent - Vdc1) * (x1 - x2) / (Vchgstart - Vdc1);

[0156] x = x1 - Δx;

[0157] y = y1 + Δx;

[0158] z = 0.

[0159] In the third power conversion stage, the SOC1, SOC2, and SOC3 estimations all play a role. The first weight value information at the start of the third power conversion stage satisfies x + y + z = 1. Using the second weight information at the end of the second power conversion stage as the first weight information at the start of the third power conversion stage, define the second weight information at the end of the third power conversion stage as x3, y3, z3. During the third power conversion stage, as the voltage rises, x continues to decrease, y also gradually decreases, and z gradually increases. Define the weight adjustment amounts of x and y during the third power conversion stage as Δx and Δy, and their calculation formulas are as follows:

[0160] Δx = (Vcurrent - Vchgstart) * (x2 - x3) / (VchgLmt - Vchgstart);

[0161] Δy = (Vcurrent - Vchgstart) * (y2 - y3) / (VchgLmt - Vchgstart);

[0162] x = x2 - Δx;

[0163] y = y2 - Δy;

[0164] z = z3 + Δx + Δy.

[0165] S550. Determine the second state of charge estimation value of the energy storage battery according to at least one first state of charge estimation value and the weight of each first state of charge estimation value.

[0166] The technical solution of the embodiments of the present invention, in addition to achieving the technical effects of the foregoing embodiments, determines its weight by considering the relationship between each first state of charge estimation method and the first voltage of the energy storage battery, and then determines the weight of each first state of charge estimation value. It can integrate the advantages of multiple estimation methods, make full use of the accuracy of different estimation methods under different voltage conditions, make the finally obtained second state of charge estimation value closer to the true state of charge of the battery, and reduce the estimation error. Moreover, dynamically adjusting the weights of each estimation method according to the first voltage of the battery can better adapt to the characteristic changes of the battery under different voltages, and improve the adaptability and robustness of the state of charge estimation. By integrating multiple first state of charge estimation values and fusing them according to the weights of their corresponding estimation methods, the effective integration and utilization of data are realized. This method of multi-source data fusion can fully exploit the information contained in different estimation methods and is more reliable and comprehensive than a single estimation method.

[0167] According to an embodiment of the present invention, the process described above with reference to the flowchart can be applied to an energy storage system. For example, an embodiment of the present invention includes an energy storage system, which includes: at least one battery module; at least one battery management system, where the at least one battery management system corresponds one-to-one with the at least one battery module, the battery management system is electrically connected to the corresponding battery module, and the battery management system is used to include program code for executing the battery power detection method shown in the flowchart.

[0168] In such an embodiment, the energy storage system provided by the present application is applicable to a variety of application scenarios, such as the grid-connected power generation energy storage field, the off-grid photovoltaic energy storage field (for powering electrical equipment in households, RVs, and yachts), the wind power energy storage field, the electric equipment field, etc., which can be specifically determined according to the actual application scenario and will not be limited here. Hereinafter, the off-grid photovoltaic energy storage field will be taken as an example for illustration, and the other application scenarios are basically similar and will not be elaborated.

[0169] In the off-grid photovoltaic energy storage application scenario, a complete photovoltaic energy storage system at least includes a photovoltaic power generation system, a power conversion system, an energy storage system, and an electrical load system. The photovoltaic power generation system is composed of several solar panels connected in series and parallel, and is used to convert solar energy into electrical energy. The power conversion system injects the electrical energy generated by the photovoltaic power generation system into the energy storage system for storage, and the electrical load system then adapts the electrical energy stored in the energy storage system to the power required by the electrical equipment. The aforementioned power conversion system can usually be implemented by a DC / DC converter with MPPT function, and the electrical load system can usually be implemented by a DC / DC converter and a DC / AC converter. Here, the energy storage system will be mainly introduced. The energy storage system is usually composed of connecting multiple battery packs to each other. Using battery packs in series can increase the output voltage of the battery pack, and using battery packs in parallel can obtain a larger battery capacity. Therefore, in order to obtain an energy storage system with a target voltage level and capacity, users will connect multiple battery packs in series and parallel with each other to obtain a high-voltage and large-capacity energy storage system for energy storage and power supply. In addition, for the convenience of centralized and unified control, each battery pack in the energy storage system is usually also provided with a communication interface, and the battery packs can communicate with each other through means such as CAN bus, RS485 bus, RS232 bus, etc. At present, with the further development of the new energy industry and the extension of application scenarios, higher requirements are put forward for the performance of the energy storage system, including system stability and consistency, waterproof and dustproof, and safety level, etc.

[0170] In an optional but non-limiting implementation manner, the solution of the present application also provides a photovoltaic power generation system, which includes: a photovoltaic power generation component, a controller, and the energy storage system according to any one of the above embodiments; the photovoltaic power generation component is used to convert solar energy into direct current electrical energy; the controller is used to store the direct current electrical energy in the energy storage system.

[0171] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is made herein.

[0172] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for detecting battery power, characterized in that, The method includes: Determining a first voltage of the energy storage battery, where the first voltage is the battery terminal voltage when the energy storage battery performs power conversion under a first operating condition, and the first operating condition is charging or discharging of the energy storage battery; Determining at least one first state of charge (SOC) estimate value according to the first voltage, where each first SOC estimate value is obtained by estimating the SOC of the energy storage battery using a corresponding SOC estimation method, and the SOC estimation method used for the SOC estimation of the energy storage battery is related to the battery terminal voltage of the energy storage battery; Determining a second SOC estimate value of the energy storage battery according to the at least one first SOC estimate value.

2. The method according to claim 1, wherein Determining at least one first SOC estimate value according to the first voltage includes: Determining at least one first SOC estimation method associated with the first voltage from several first SOC estimation methods, where the first voltage is used to identify the power conversion stage in which the energy storage battery is located when performing power conversion under the first operating condition, and the applicable SOC estimation methods for the energy storage battery in different power conversion stages are different; Estimating the SOC of the energy storage battery according to the at least one first SOC estimation method to obtain at least one first SOC estimate value.

3. The method according to claim 2, wherein Determining at least one first SOC estimation method associated with the first voltage from several first SOC estimation methods includes: Determining a second voltage and a third voltage of the energy storage battery, where the second voltage and the third voltage form several voltage intervals as voltage critical values for dividing different power conversion stages experienced by the energy storage battery when performing power conversion under the first operating condition; Determining at least one first SOC estimation method from several first SOC estimation methods according to the first voltage, the second voltage, and the third voltage.

4. The method according to claim 3, characterized in that, The second voltage is the reference voltage among the respective reference battery terminal voltages; each reference battery terminal voltage is the battery terminal voltage that is the same as the voltage determined by mapping the temperature and current rate of the energy storage battery at the first voltage for each charge state correction point among the respective battery terminal voltages recorded for each charge state correction point; different charge states are recorded for each of the charge state correction points, and there is a mutual mapping relationship between each charge state and at least one battery terminal voltage; The third voltage is used to represent the battery terminal voltage at the start of the final stage of the first operating condition of the energy storage battery.

5. The method according to claim 4, characterized in that When the first operating condition is charging of the energy storage battery, the reference voltage is the minimum voltage among the respective reference battery terminal voltages; when the first operating condition is discharging of the energy storage battery, the reference voltage is the maximum voltage among the respective reference battery terminal voltages.

6. The method according to claim 3, characterized in that Determining at least one first SOC estimation method from several first SOC estimation methods according to the first voltage, the second voltage, and the third voltage includes: When the first voltage is within the first voltage range, determine the first type of state-of-charge (SOC) estimation method among the several first SOC estimation methods as the at least one first SOC estimation method, where the first type of SOC estimation method is the method of estimating the SOC using ampere-hour integration. When the first voltage is within the second voltage range, determine the first type of SOC estimation method and the second type of SOC estimation method among the several first SOC estimation methods as the at least one first SOC estimation method, where the second type of SOC estimation method is the method of estimating the SOC using the mapping relationship between the battery terminal voltage and the SOC for compensating the charge-discharge efficiency error caused by the change in the battery characteristics of the energy storage battery. When the first voltage is within the third voltage range, determine the first type of SOC estimation method, the second type of SOC estimation method, and the third type of SOC estimation method among the several first SOC estimation methods as the at least one first SOC estimation method, where the third type of SOC estimation method is the method of estimating the SOC through interpolation compensation using the pre-acquired SOCs of the energy storage battery at different battery terminal voltages; the second type of SOC estimation method is used to compensate for the cumulative error in estimating the SOC of the first type of SOC estimation method caused by the charge-discharge efficiency error due to the change in the battery characteristics of the energy storage battery; the third type of SOC estimation method is used to suppress the jump in the SOC of the energy storage battery after the start of the end stage of the first working condition caused by the calibration error of the mapping relationship between the battery terminal voltage and the SOC of the energy storage battery. Among them, the first voltage range, the second voltage range, and the third voltage range respectively correspond to several voltage ranges formed by the second voltage and the third voltage as voltage critical values. When the first working condition is the charging condition of the energy storage battery, the first voltage range is the range where the voltage is less than the second voltage, the second voltage range is the range where the voltage is not less than the second voltage and less than the third voltage, and the third voltage range is the range where the voltage is not less than the third voltage; when the first working condition is the discharging condition of the energy storage battery, the first voltage range is the range where the voltage is greater than the second voltage, the second voltage range is the range where the voltage is not greater than the second voltage and greater than the third voltage, and the third voltage range is the range where the voltage is not greater than the third voltage.

7. The method according to claim 2, wherein Determine the second state-of-charge (SOC) estimation value of the energy storage battery according to the at least one first SOC estimation value, including: Determine the weight of each of the at least one first state of charge estimate, where the weight of each first state of charge estimate depends on the weight of the first state of charge estimation method corresponding to the first state of charge estimate, and the weight of each first state of charge estimation method is related to the first voltage of the energy storage battery; Determine the second state of charge estimate of the energy storage battery according to the at least one first state of charge estimate and the weight of each first state of charge estimate.

8. The method according to claim 7, wherein Determining the weight of each of the at least one first state of charge estimate includes: Determine the first weight information and the second weight information associated with the first voltage of the energy storage battery. The first weight information is used to indicate the weights of the respective first state of charge estimation methods configured at the start of the power conversion stage when the energy storage battery is at the first voltage, and the second weight information is used to indicate the weights of the respective first state of charge estimation methods configured at the end of the power conversion stage when the energy storage battery is at the first voltage; Determine the weight of each of the at least one first state of charge estimate according to the first voltage and the first weight information and the second weight information associated with the first voltage.

9. The method according to claim 8, wherein When the first voltage is in the first voltage range, only the first type of state of charge estimation method is included in the at least one first state of charge estimation method, and the weight of the first type of state of charge estimation method is configured as the weight of the first type of state of charge estimation method indicated by the first weight information associated with the first voltage. The first weight information associated with the first voltage is the same as the second weight information, and the weight of the first type of state of charge estimation method indicated is a preset value, and the preset value is 1; When the first voltage is in the second voltage range, the at least one first state of charge estimation method includes the first type of state of charge estimation method and the second type of state of charge estimation method. Based on the weights of the respective types of state of charge estimation methods indicated by the first weight information associated with the first voltage, the weight of the first type of state of charge estimation method is adjusted negatively with the change of the first voltage, and the weight of the second type of state of charge estimation method is adjusted positively with the change of the first voltage; When the first voltage is in the third voltage range, the at least one first state of charge estimation method includes a first type of state of charge estimation method, a second type of state of charge estimation method, and a third type of state of charge estimation method. Based on the weights of each type of state of charge estimation method indicated by the first weight information associated with the first voltage, the weight of the first type of state of charge estimation method is negatively correlated with the change of the first voltage, the weight of the second type of state of charge estimation method is negatively correlated with the change of the first voltage, and the weight of the third type of state of charge estimation method is positively correlated with the change of the first voltage; Wherein, when the first working condition is the working condition of charging the energy storage battery, the first voltage range is the range where the voltage is less than the second voltage, the second voltage range is the range where the voltage is not less than the second voltage and less than the third voltage, and the third voltage range is the range where the voltage is not less than the third voltage; when the first working condition is the working condition of discharging the energy storage battery, the first voltage range is the range where the voltage is greater than the second voltage, the second voltage range is the range where the voltage is not greater than the second voltage and greater than the third voltage, and the third voltage range is the range where the voltage is not greater than the third voltage; the first type of state of charge estimation method is the method of estimating the state of charge by ampere-hour integration; the second type of state of charge estimation method is the method of estimating the state of charge by using the mapping relationship between the battery terminal voltage and the state of charge of the energy storage battery for the charge-discharge efficiency error caused by the change of the battery characteristics of the energy storage battery; the third type of state of charge estimation method is the method of estimating the state of charge by interpolation compensation by using the state of charge of the energy storage battery obtained in advance at different battery terminal voltages; the second type of state of charge estimation method is used to compensate the cumulative error of the state of charge estimation caused by the first type of state of charge estimation method caused by the charge-discharge efficiency error caused by the change of the battery characteristics of the energy storage battery; the third type of state of charge estimation method is used to suppress the state of charge jump of the energy storage battery after the start of the end stage of the first working condition caused by the calibration error of the mapping relationship between the battery terminal voltage and the state of charge of the energy storage battery.

10. The method according to claim 8, characterized in that Determining the weight of each of the at least one first state of charge estimate according to the first voltage and the first weight information and the second weight information associated with the first voltage includes: Determining the weight difference associated with the first voltage according to the first weight information and the second weight information associated with the first voltage, where the weight difference associated with the first voltage is the difference between the weights of each first state of charge estimation method indicated by the first weight information and the second weight information associated with the first voltage; Determine the voltage difference associated with the first voltage according to the first voltage and the fifth voltage, where the voltage difference associated with the first voltage is represented by the absolute value of the difference between the first voltage and the fifth voltage, the fifth voltage is the starting voltage of the reference voltage range among several voltage ranges formed by using the second voltage and the third voltage as voltage critical values, and the first voltage is within the reference voltage range; According to the voltage difference associated with the first voltage and the weight difference associated with the first voltage, the weight adjustment amount of each first state of charge estimation method associated with the first voltage; According to the weight adjustment amount of each first state of charge estimation method associated with the first voltage, adjust the first weight information associated with the first voltage to obtain the weight of each first state of charge estimation value among the at least one first state of charge estimation value.

11. An energy storage system, characterized in that, Comprising: At least one battery module; at least one battery management system, where the at least one battery management system corresponds to the at least one battery module one by one, the battery management system is electrically connected to the corresponding battery module, and the battery management system is used to execute the battery power detection method described in any one of claims 1-10.

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