Equivalent model establishment method and system for energy storage battery module

Abstract

The present invention discloses a method for establishing an equivalent model of an energy storage battery module, comprising determining the number and connection relationship of battery cells in a target energy storage battery module; establishing an equivalent circuit model of the battery cells and several equivalent circuit models of the energy storage battery module and determining the parameters to be identified of the models; obtaining voltage and current data information of the target energy storage battery module; calculating the parameters to be identified of each model of the target energy storage battery module; calculating the difference data between the several equivalent circuit models and the voltage data of the target energy storage battery module; selecting the equivalent circuit model of the target energy storage battery module based on the difference data, and completing the establishment of the equivalent model of the target energy storage battery module. The present invention also discloses a system for implementing the method for establishing an equivalent model of the energy storage battery module. The present invention can not only realize the establishment of an equivalent model of the energy storage battery module, but also has higher reliability, better accuracy, and higher efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of electrical automation, and in particular relates to a method and system for establishing an equivalent model of an energy storage battery module. Background Art

[0002] With the development of economy and technology and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and life, bringing endless convenience to people's production and life. Therefore, ensuring a stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] Environmental pollution is becoming increasingly serious. Consequently, an increasing number of renewable energy generators are being integrated into power systems. The randomness, intermittency, and volatility of renewable energy generator output pose significant challenges to the safe operation of power systems. Energy storage batteries, with their significant advantages of fast response, high control precision, and short construction cycles, can effectively address the power system security and stability challenges associated with the integration of a high proportion of renewable energy generators.

[0004] Energy storage battery modules are made up of battery modules connected in series or parallel, which in turn are formed by connecting battery cells in series or parallel. Accurate modeling of energy storage battery modules is crucial for improving the control and safety of battery management systems.

[0005] At present, the modeling schemes for energy storage battery modules mainly include overall modeling schemes, simplified modeling schemes and combined modeling schemes. Among them, the overall modeling scheme models the energy storage battery module as a single battery. Although this scheme is simple and fast, its accuracy and reliability are poor. The simplified modeling scheme models the energy storage battery module by taking the state of a single battery cell in the battery module as the state of the entire battery module. This scheme also ignores the inconsistency between battery cells, and its reliability and accuracy are also poor. The combined modeling scheme models all battery cells in the energy storage battery module separately. Although the model accuracy is high, the scheme is complex and the efficiency is low. Summary of the Invention

[0006] One of the objectives of the present invention is to provide a method for establishing an equivalent model of an energy storage battery module with high reliability, good accuracy and high efficiency.

[0007] A second object of the present invention is to provide a system for implementing the method for establishing an equivalent model of the energy storage battery module.

[0008] The method for establishing an equivalent model of the energy storage battery module provided by the present invention comprises the following steps:

[0009] S1. Determine the number and connection relationship of battery cells in the target energy storage battery module;

[0010] S2 establishes an equivalent circuit model of a battery cell, and based on the data information obtained in step S1, establishes several equivalent circuit models of the energy storage battery module and determines the parameters to be identified for the model;

[0011] S3 obtains the voltage and current data information of the target energy storage battery module;

[0012] S4. Using the data information obtained in step S3, the parameters to be identified of each model of the target energy storage battery module in step S2 are calculated;

[0013] S5. Calculate the difference data between the voltage data of several equivalent circuit models and the target energy storage battery module;

[0014] S6. Based on the difference data calculated in step S5, an equivalent circuit model of the target energy storage battery module is selected to complete the establishment of the equivalent model of the target energy storage battery module.

[0015] Determining the number and connection relationship of battery cells in the target energy storage battery module in step S1 specifically includes the following steps:

[0016] Determine the number N of battery cells in the target energy storage battery module;

[0017] Determine the connection relationship of the battery cells in the target energy storage battery module; the connection relationship includes a series-first, parallel-later connection relationship and a parallel-first, series-later connection relationship; the series-first, parallel-later connection relationship is specifically that every S1 battery cells are connected in series to form a battery module, and then P1 battery modules are connected in parallel to form the energy storage battery module; the parallel-first, series-later connection relationship is specifically that every P2 battery cells are connected in parallel to form a battery module, and then S2 battery modules are connected in series to form the energy storage battery module;

[0018] If the connection relationship is serial first and then parallel, then N = S1*P1;

[0019] If the connection relationship is parallel first and then serial, then N=P2*S2.

[0020] The step S2 of establishing an equivalent circuit model of a battery cell and, based on the data information obtained in step S1, establishing several equivalent circuit models of the energy storage battery module and determining the parameters to be identified of the model specifically includes the following steps:

[0021] Establish an n-order RC equivalent circuit model of the battery cell; establish the state equation of the battery cell, including:

[0022] State of charge equation:

[0023] Open circuit voltage equation:

[0024] Internal resistance voltage equation: U0(t)=I(t)R0(t)

[0025] Polarization voltage equation:

[0026] Terminal voltage equation: Where SOC(t) is the SOC state value at time t; SOC0 is the initial SOC value; Q n is the rated capacity of the battery cell; I(t) is the operating current of the battery cell at time t; U oc (t) is the open circuit voltage of the battery cell at time t; N1 is the number of fitting terms of the polynomial function; are the coefficients of the polynomial function; U0(t) is the internal resistance voltage of the battery cell; R0(t) is the internal resistance of the battery cell at time t; U δ (t) is the voltage on the δth RC link; C δ (t) is the polarization capacitance of the battery cell; R δ (t) is the polarization resistance of the battery cell; U(t) is the terminal voltage of the battery cell at time t;

[0027] The parameters to be identified in the model include the internal resistance R0(t) of the battery cell, the polarization resistance R δ (t) and the polarization capacitance C of the battery cell δ (t);

[0028] R0(t) is expressed as α i are the coefficients of the internal resistance fitting polynomial;

[0029] R δ (t) is expressed as β i are the coefficients of the polarization resistance fitting polynomial;

[0030] C δ (t) is expressed as γ i are the coefficients of the fitting polynomial for polarization capacitance;

[0031] Several equivalent circuit models of the energy storage resistor module are established, including:

[0032] The target energy storage battery is modeled using the overall modeling method;

[0033] The target energy storage battery is modeled using a simplified modeling method;

[0034] The target energy storage battery is modeled using a combined modeling method.

[0035] The step S3 of obtaining the voltage and current data information of the target energy storage battery module specifically includes the following steps:

[0036] For the overall modeling method, pulse discharge experiments are conducted on the target energy storage battery module at different SOC values ​​to obtain voltage and current data of the target battery pack;

[0037] For the simplified modeling method and the combined modeling method, pulse discharge experiments are performed on the battery cells in the target energy storage battery at different SOC values ​​to obtain the voltage data and current data of the battery cells in the target battery pack.

[0038] Step S4 uses the data information obtained in step S3 to calculate the parameters to be identified for each model of the target energy storage battery module in step S2, which specifically includes the following steps:

[0039] Using the data information obtained in step S3, the parameters to be identified of each model of the target energy storage battery module are solved based on an iterative algorithm;

[0040] The iterative algorithm includes least squares method, particle swarm optimization algorithm, neural network algorithm or conjugate gradient algorithm.

[0041] The step S5 of calculating the difference data between the voltage data of the plurality of equivalent circuit models and the target energy storage battery module specifically includes the following steps:

[0042] For the equivalent circuit models established by different modeling methods, the following formula is used to calculate the square difference data SSE between the terminal voltage simulation value of each equivalent circuit model and the terminal voltage measurement value of the target battery module:

[0043]

[0044] In the formula is the terminal voltage simulation value; U t is the terminal voltage measurement value; the total number of sampling points k;

[0045] According to the obtained square difference data, the root mean square difference RMSE of each equivalent circuit model is calculated as follows:

[0046]

[0047] Step S6, based on the difference data calculated in step S5, selects the equivalent circuit model of the target energy storage battery module to complete the establishment of the equivalent model of the target energy storage battery module, specifically including the following steps:

[0048] Based on the difference data calculated in step S5, the evaluation index value BIC of each equivalent circuit model is calculated using the following formula:

[0049]

[0050] Where m is the parameter to be identified of the equivalent circuit model; d is the set parameter;

[0051] Finally, the equivalent circuit model with the smallest evaluation index value BIC is selected as the equivalent circuit model of the target energy storage battery module, completing the establishment of the equivalent model of the target energy storage battery module.

[0052] The present invention also provides a system for implementing the method for establishing an equivalent model of the energy storage battery module, comprising a data acquisition module, a primary modeling module, an experimental test module, a parameter calculation module, a difference calculation module and an equivalent modeling module; the data acquisition module, the primary modeling module, the experimental test module, the parameter calculation module, the difference calculation module and the equivalent modeling module are connected in series in sequence; the data acquisition module is used to determine the number and connection relationship of battery cells in the target energy storage battery module, and upload the data information to the primary modeling module; the primary modeling module is used to establish an equivalent circuit model of the battery cell according to the received data information, and based on the acquired data information, establish several equivalent circuit models of the energy storage battery module and determine the parameters to be identified of the model, and upload the data information to the experimental test module; The test module is used to obtain the voltage and current data information of the target energy storage battery module based on the received data information, and upload the data information to the parameter calculation module; the parameter calculation module is used to calculate the parameters to be identified of each model of the target energy storage battery module in step S2 using the obtained data information based on the received data information, and upload the data information to the difference calculation module; the difference calculation module is used to calculate the difference data between several equivalent circuit models and the voltage data of the target energy storage battery module based on the received data information, and upload the data information to the equivalent modeling module; the equivalent modeling module is used to select the equivalent circuit model of the target energy storage battery module based on the received data information and the calculated difference data, and complete the establishment of the equivalent model of the target energy storage battery module.

[0053] The method and system for establishing an equivalent model of an energy storage battery module provided by the present invention selects an equivalent model of the energy storage battery module through a designed calculation scheme based on the characteristics of several equivalent circuit models of the energy storage battery module and experimental data. Therefore, the present invention not only enables the establishment of an equivalent model of the energy storage battery module, but also has higher reliability, better accuracy, and higher efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Schematic diagram of the process flow of the present invention.

[0055] Figure 2 Schematic diagram of the n-RC equivalent circuit of the battery cell in the method of the present invention.

[0056] Figure 3 Schematic diagram of overall modeling, simplified modeling and combined modeling of the energy storage battery module in the method of the present invention.

[0057] Figure 4 Schematic diagram of the functional modules of the system of the present invention. DETAILED DESCRIPTION

[0058] like Figure 1 The figure shows a schematic flow chart of the method of the present invention: The method for establishing an equivalent model of the energy storage battery module disclosed in the present invention comprises the following steps:

[0059] S1. Determine the number and connection relationship of battery cells in the target energy storage battery module; specifically include the following steps:

[0060] Determine the number N of battery cells in the target energy storage battery module;

[0061] Determine the connection relationship of the battery cells in the target energy storage battery module; the connection relationship includes a series-first, parallel-later connection relationship and a parallel-first, series-later connection relationship; the series-first, parallel-later connection relationship is specifically that every S1 battery cells are connected in series to form a battery module, and then P1 battery modules are connected in parallel to form the energy storage battery module; the parallel-first, series-later connection relationship is specifically that every P2 battery cells are connected in parallel to form a battery module, and then S2 battery modules are connected in series to form the energy storage battery module;

[0062] If the connection relationship is serial first and then parallel, then N = S1*P1;

[0063] If the connection relationship is parallel first and then serial, then N = P2*S2;

[0064] S2. Establish an equivalent circuit model of the battery cell, and based on the data information obtained in step S1, establish several equivalent circuit models of the energy storage battery module and determine the parameters to be identified of the model; specifically comprising the following steps:

[0065] Establish the n-order RC equivalent circuit model of the battery cell, such as Figure 2 As shown; establish the state equation of the battery cell, including:

[0066] State of charge equation:

[0067] Open circuit voltage equation:

[0068] Internal resistance voltage equation: U0(t)=I(t)R0(t)

[0069] Polarization voltage equation:

[0070] Terminal voltage equation: Where SOC(t) is the SOC state value at time t; SOC0 is the initial SOC value; Q n is the rated capacity of the battery cell; I(t) is the operating current of the battery cell at time t; U oc (t) is the open circuit voltage of the battery cell at time t; N1 is the number of fitting terms of the polynomial function; are the coefficients of the polynomial function; U0(t) is the internal resistance voltage of the battery cell; R0(t) is the internal resistance of the battery cell at time t; U δ (t) is the voltage on the δth RC link; C δ (t) is the polarization capacitance of the battery cell; R δ (t) is the polarization resistance of the battery cell; U(t) is the terminal voltage of the battery cell at time t;

[0071] The parameters to be identified in the model include the internal resistance R0(t) of the battery cell, the polarization resistance R δ (t) and the polarization capacitance C of the battery cell δ (t);

[0072] R0(t) is expressed as α i are the coefficients of the internal resistance fitting polynomial;

[0073] R δ (t) is expressed as β i are the coefficients of the polarization resistance fitting polynomial;

[0074] C δ (t) is expressed as γ i are the coefficients of the fitting polynomial for polarization capacitance;

[0075] Several equivalent circuit models of the energy storage resistor module are established, including:

[0076] The target energy storage battery is modeled using the overall modeling method;

[0077] The target energy storage battery is modeled using a simplified modeling method;

[0078] The target energy storage battery is modeled using a combined modeling method;

[0079] like Figure 3 As shown in the figure, the overall modeling method treats the target energy storage battery as a whole battery for modeling; the simplified modeling method ignores the differences between battery modules, that is, the model parameters of battery cell #1 (#3) and battery cell #2 (#4) are the same, so only battery cells #1 and #3 need to be identified; the combined modeling rule identifies battery cells #1, #2, #3 and #4;

[0080] S3. Obtaining voltage and current data information of the target energy storage battery module; specifically comprising the following steps:

[0081] For the overall modeling method, pulse discharge experiments are conducted on the target energy storage battery module at different SOC values ​​to obtain voltage and current data of the target battery pack;

[0082] For the simplified modeling method and the combined modeling method, pulse discharge experiments are performed on the battery cells in the target energy storage battery at different SOC values ​​to obtain the voltage and current data of the battery cells in the target battery pack;

[0083] S4. Using the data information obtained in step S3, the parameters to be identified of each model of the target energy storage battery module in step S2 are calculated; specifically comprising the following steps:

[0084] Using the data information obtained in step S3, the parameters to be identified of each model of the target energy storage battery module are solved based on an iterative algorithm;

[0085] The iterative algorithm includes least squares method, particle swarm optimization algorithm, neural network algorithm or conjugate gradient algorithm;

[0086] S5. Calculating the difference data between the voltage data of the equivalent circuit models and the target energy storage battery module; specifically comprising the following steps:

[0087] For the equivalent circuit models established by different modeling methods, the following formula is used to calculate the square difference data SSE between the terminal voltage simulation value of each equivalent circuit model and the terminal voltage measurement value of the target battery module:

[0088]

[0089] In the formula is the terminal voltage simulation value; U t is the terminal voltage measurement value; the total number of sampling points of k;

[0090] According to the obtained square difference data, the root mean square difference RMSE of each equivalent circuit model is calculated using the following formula:

[0091] S6. Based on the difference data calculated in step S5, an equivalent circuit model of the target energy storage battery module is selected to complete the establishment of the equivalent model of the target energy storage battery module; specifically comprising the following steps:

[0092] Based on the difference data calculated in step S5, the evaluation index value BIC of each equivalent circuit model is calculated using the following formula:

[0093]

[0094] Where m is the parameter to be identified of the equivalent circuit model; d is the set parameter;

[0095] Finally, the equivalent circuit model with the smallest evaluation index value BIC is selected as the equivalent circuit model of the target energy storage battery module, completing the establishment of the equivalent model of the target energy storage battery module.

[0096] like Figure 4 The figure shows a schematic diagram of the functional modules of the system of the present invention: the system disclosed in the present invention for realizing the method for establishing an equivalent model of the energy storage battery module includes a data acquisition module, a primary modeling module, an experimental test module, a parameter calculation module, a difference calculation module and an equivalent modeling module; the data acquisition module, the primary modeling module, the experimental test module, the parameter calculation module, the difference calculation module and the equivalent modeling module are connected in series in sequence; the data acquisition module is used to determine the number and connection relationship of the battery cells in the target energy storage battery module, and upload the data information to the primary modeling module; the primary modeling module is used to establish an equivalent circuit model of the battery cell according to the received data information, and based on the acquired data information, establish several equivalent circuit models of the energy storage battery module and determine the parameters to be identified of the model, and upload the data information Experimental testing module; the experimental testing module is used to obtain the voltage and current data information of the target energy storage battery module based on the received data information, and upload the data information to the parameter calculation module; the parameter calculation module is used to calculate the parameters to be identified of each model of the target energy storage battery module in step S2 using the obtained data information based on the received data information, and upload the data information to the difference calculation module; the difference calculation module is used to calculate the difference data between several equivalent circuit models and the voltage data of the target energy storage battery module based on the received data information, and upload the data information to the equivalent modeling module; the equivalent modeling module is used to select the equivalent circuit model of the target energy storage battery module based on the received data information and the calculated difference data, and complete the establishment of the equivalent model of the target energy storage battery module.

Claims

1. A method for establishing an equivalent model of an energy storage battery module, comprising the following steps: S1. Determine the number and connection relationship of battery cells in the target energy storage battery module; S2. Establish an equivalent circuit model of the battery cell, and based on the data information obtained in step S1, establish several equivalent circuit models of the energy storage battery module and determine the parameters to be identified of the model; specifically comprising the following steps: Establish an n-order RC equivalent circuit model of the battery cell; establish the state equation of the battery cell, including: State of charge equation: Open circuit voltage equation: Internal resistance voltage equation: U0(t)=I(t)R0(t) Polarization voltage equation: Terminal voltage equation: Where SOC(t) is the SOC state value at time t; SOC0 is the initial SOC value; Q n is the rated capacity of the battery cell; I(t) is the operating current of the battery cell at time t; U oc (t) is the open circuit voltage of the battery cell at time t; N1 is the number of fitting terms of the polynomial function; are the coefficients of the polynomial function; U0(t) is the internal resistance voltage of the battery cell; R0(t) is the internal resistance of the battery cell at time t; U δ (t) is the voltage on the δth RC link; C δ (t) is the polarization capacitance of the battery cell; R δ (t) is the polarization resistance of the battery cell; U(t) is the terminal voltage of the battery cell at time t; The parameters to be identified in the model include the internal resistance R0(t) of the battery cell, the polarization resistance R δ (t) and the polarization capacitance C of the battery cell δ (t); R0(t) is expressed as α i are the coefficients of the internal resistance fitting polynomial; R δ (t) is expressed as β i are the coefficients of the polarization resistance fitting polynomial; C δ (t) is expressed as γ i are the coefficients of the fitting polynomial for polarization capacitance; Several equivalent circuit models of the energy storage resistor module are established, including: The target energy storage battery is modeled using the overall modeling method; The target energy storage battery is modeled using a simplified modeling method; The target energy storage battery is modeled using a combined modeling method; S3 obtains the voltage and current data information of the target energy storage battery module; S4. Using the data information obtained in step S3, the parameters to be identified of each model of the target energy storage battery module in step S2 are calculated; S5. Calculate the difference data between the voltage data of several equivalent circuit models and the target energy storage battery module; S6. According to the difference data calculated in step S5, an equivalent circuit model of the target energy storage battery module is selected to complete the establishment of an equivalent model of the target energy storage battery module; During specific implementation, based on the established equivalent circuit models of the target energy storage battery, the square difference data between the terminal voltage simulation value of each equivalent circuit model and the terminal voltage measurement value of the target battery module and the root mean square difference data of each equivalent circuit model are calculated, and the evaluation index value BIC of each equivalent circuit model is calculated based on the obtained root mean square difference data, and the equivalent circuit model with the smallest evaluation index value BIC is selected as the equivalent circuit model of the target energy storage battery module to complete the establishment of the equivalent model of the target energy storage battery module.

2. The method for establishing an equivalent model of an energy storage battery module according to claim 1, characterized in that Determining the number and connection relationship of battery cells in the target energy storage battery module in step S1 specifically includes the following steps: Determine the number N of battery cells in the target energy storage battery module; Determine the connection relationship of the battery cells in the target energy storage battery module; the connection relationship includes a series-first, parallel-later connection relationship and a parallel-first, series-later connection relationship; the series-first, parallel-later connection relationship is specifically that every S1 battery cells are connected in series to form a battery module, and then P1 battery modules are connected in parallel to form the energy storage battery module; the parallel-first, series-later connection relationship is specifically that every P2 battery cells are connected in parallel to form a battery module, and then S2 battery modules are connected in series to form the energy storage battery module; If the connection relationship is serial first and then parallel, then N = S1*P1; If the connection relationship is parallel first and then serial, then N=P2*S2.

3. The method for establishing an equivalent model of an energy storage battery module according to claim 2, characterized in that The step S3 of obtaining the voltage and current data information of the target energy storage battery module specifically includes the following steps: For the overall modeling method, pulse discharge experiments are conducted on the target energy storage battery module at different SOC values ​​to obtain voltage and current data of the target battery pack; For the simplified modeling method and the combined modeling method, pulse discharge experiments are performed on the battery cells in the target energy storage battery at different SOC values ​​to obtain the voltage data and current data of the battery cells in the target battery pack.

4. The method for establishing an equivalent model of an energy storage battery module according to claim 3, characterized in that Step S4 uses the data information obtained in step S3 to calculate the parameters to be identified for each model of the target energy storage battery module in step S2, which specifically includes the following steps: Using the data information obtained in step S3, the parameters to be identified of each model of the target energy storage battery module are solved based on an iterative algorithm; The iterative algorithm includes least squares method, particle swarm optimization algorithm, neural network algorithm or conjugate gradient algorithm.

5. The method for establishing an equivalent model of an energy storage battery module according to claim 4, characterized in that The step S5 of calculating the difference data between the voltage data of the plurality of equivalent circuit models and the target energy storage battery module specifically includes the following steps: For the equivalent circuit models established by different modeling methods, the following formula is used to calculate the square difference data SSE between the terminal voltage simulation value of each equivalent circuit model and the terminal voltage measurement value of the target battery module: In the formula is the terminal voltage simulation value; U t is the terminal voltage measurement value; the total number of sampling points k; According to the obtained square difference data, the root mean square difference RMSE of each equivalent circuit model is calculated and 6. The method for establishing an equivalent model of an energy storage battery module according to claim 5, characterized in that Step S6, based on the difference data calculated in step S5, selects the equivalent circuit model of the target energy storage battery module to complete the establishment of the equivalent model of the target energy storage battery module, specifically including the following steps: Based on the difference data calculated in step S5, the evaluation index value BIC of each equivalent circuit model is calculated using the following formula: Where m is the parameter to be identified of the equivalent circuit model; d is the set parameter; Finally, the equivalent circuit model with the smallest evaluation index value BIC is selected as the equivalent circuit model of the target energy storage battery module, completing the establishment of the equivalent model of the target energy storage battery module.

7. A system for implementing the method for establishing an equivalent model of an energy storage battery module according to any one of claims 1 to 6, characterized in that It includes a data acquisition module, a primary modeling module, an experimental testing module, a parameter calculation module, a difference calculation module and an equivalent modeling module; the data acquisition module, the primary modeling module, the experimental testing module, the parameter calculation module, the difference calculation module and the equivalent modeling module are connected in series in sequence; the data acquisition module is used to determine the number and connection relationship of battery cells in the target energy storage battery module, and upload the data information to the primary modeling module; The primary modeling module is used to establish an equivalent circuit model of the battery cell based on the received data information, and based on the acquired data information, establish several equivalent circuit models of the energy storage battery module and determine the parameters to be identified of the model, and upload the data information to the experimental testing module; the experimental testing module is used to obtain the voltage and current data information of the target energy storage battery module based on the received data information, and upload the data information to the parameter calculation module; The parameter calculation module is used to calculate the parameters to be identified of each model of the target energy storage battery module in step S2 based on the received data information and the acquired data information, and upload the data information to the difference calculation module; The difference calculation module is used to calculate the difference data between several equivalent circuit models and the voltage data of the target energy storage battery module based on the received data information, and upload the data information to the equivalent modeling module; The equivalent modeling module is used to select the equivalent circuit model of the target energy storage battery module according to the received data information and the calculated difference data, and complete the establishment of the equivalent model of the target energy storage battery module.

Images