Battery cell equivalent model establishment method for simulation calculation in energy storage system

Abstract

The invention discloses a method for establishing a battery cell equivalent model for simulation calculation in an energy storage system, and relates to the field of battery cell equivalent models of energy storage systems, and the method comprises the following steps: S1, establishing a corresponding equation for each region to describe an internal physical and chemical process; s2, deducing the Poisson's ratio; s3, performing parameter statistics on materials used in the energy storage system; s4, establishing parameters of the orthogonal anisotropic material based on the obtained data and endowing the parameters to a model; s5, solving an equation set through a numerical method; s6, determining a circuit topological structure; s7, identifying and determining parameters; s8, verifying and adjusting the model; and S9, establishing an empirical model and then verifying the empirical model. According to the battery cell equivalent model establishment method for simulation calculation in the energy storage system, the overall performance after multiple battery cells are combined can be better understood and analyzed, the performance of the energy storage system can be accurately predicted in the design stage, optimization of the structure and parameters of the system is facilitated, and the overall performance of the system is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery cell equivalent models for energy storage systems, and in particular to a method for establishing a battery cell equivalent model for simulation calculation in an energy storage system. Background Art

[0002] An energy storage system refers to a system that stores energy through specific devices or technologies and releases it when needed.

[0003] With the widespread application of renewable energy, such as solar energy and wind energy, its power generation is intermittent and unstable, and energy storage systems are needed to store excess energy to achieve a stable energy supply. Energy storage cells are the core components of energy storage systems, and establishing their equivalent models is the basis for optimizing the design and operation of energy storage systems.

[0004] Therefore, it is necessary to propose a method for establishing a cell equivalent model for simulation calculation in energy storage systems to solve the above problems. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for establishing a cell equivalent model for simulation calculation in an energy storage system, which can effectively solve the problems in the background technology.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for establishing a cell equivalent model for simulation calculation in an energy storage system includes the following establishing steps:

[0008] S1: Based on electrochemical theory, the electrochemical reactions and ion transport processes inside lithium-ion batteries are determined and described. The space of lithium-ion battery cells is divided into different regions, and corresponding equations are established for each region to describe the physical and chemical processes inside. The elastic modulus is derived from formula 1: V f +V m =1;

[0009] Formula 2 shows that horizontal: σ1=σ f V f +σ m V m ;

[0010] Formula 3 shows that vertical: σ2=E f ε f =E m ε m =E2ε2;

[0011]

[0012] Formula 4, ε2 = ε f Vf +ε m V m ;

[0013] From formula 1, we can get:

[0014] This leads to Formula 5: E1=E f V f +E m V m ;

[0015] From formula 2 and formula 4, we can know that:

[0016] This leads to Formula 6:

[0017] S2: Derivation of Poisson's ratio: When the single layer material is ε1, the lateral strain ε2 = -U 21 ε1, the longitudinal strain of the parallel model is ε1, but there must be the same lateral contraction, and the static equilibrium condition is:

[0018] Formula 7: Vertical, σ f V f =σ m V m ;

[0019] And because, Formula 8:

[0020] Formula 9:

[0021] So we get formula 10:

[0022] S3: The volume fraction, mass fraction and mechanical parameters of lithium-ion battery materials used in energy storage systems are counted and calculated according to the formula, where Formula 11: E x =E y =∑V i E i ;

[0023] Formula 11:

[0024] Formula 12:

[0025] Formula 13: u xz =u yz =∑V i u i ;

[0026] S4: Establish parameters of orthogonal anisotropic materials based on the data obtained in S1-S3 and assign them to the model;

[0027] S5: Solve a set of partial differential equations obtained by the above steps by numerical methods, so as to obtain the changes of parameters such as voltage, current, temperature, etc. of the battery cell under different working conditions;

[0028] S6: Determine the circuit topology structure, and select a suitable equivalent circuit topology structure according to the characteristics of the lithium-ion battery cell and the simulation requirements, including but not limited to the Thevenin model and the RC model. Preferably, the Thevenin model is selected. The Thevenin model consists of an ideal voltage source, which represents the open circuit voltage of the battery cell; a series resistor, which represents the internal resistance of the battery cell; and an RC parallel circuit, which is used to simulate the dynamic characteristics of the battery cell.

[0029] S7: Parameter identification and determination: Experimentally test the voltage and current data of lithium-ion battery cells under different charging and discharging conditions, measure the terminal voltage drop of the battery cells under different discharge currents to determine the value of the series resistance, and analyze the voltage response of the battery cells during pulse charging and discharging to determine the capacitance and resistance values ​​in the RC parallel circuit;

[0030] S8: Model verification and adjustment: Apply the established model to simulation calculations and compare and verify it with the test data of the actual battery cells. If there is a large deviation, the parameters or topology of the model need to be adjusted until the model can accurately simulate the actual behavior of the battery cells.

[0031] S9: After establishing the empirical model, verify it to complete the establishment of the battery cell equivalent model.

[0032] Preferably, in step S1, V f and V m is the member f, m is the single phase, which represents the volume fraction percentage of the entire composite material, E f and E m Expressed as the elastic modulus of components f and m respectively.

[0033] Preferably, in step S1, the materials of the lithium-ion battery include aluminum foil, positive electrode material, copper foil, graphite, a separator, an electrolyte and a lead plastic film.

[0034] Preferably, in step S9, establishing an empirical model includes the following steps:

[0035] S901: Collect experimental data, conduct a large number of battery cell charge and discharge experiments, and record the performance parameters of the battery cells under different working conditions, such as voltage, capacity, internal resistance, etc. The working conditions include but are not limited to different charge and discharge currents, different temperatures, and different states of charge;

[0036] S902: Select a fitting method. According to the characteristics of the experimental data and the characteristics of the battery cell to be simulated, select an appropriate mathematical fitting method, including but not limited to polynomial fitting, exponential fitting, and logarithmic fitting. When it is found that the voltage of the battery cell shows an approximately linear relationship with the change of the charge and discharge current, a linear fitting method is used.

[0037] S903: Establishing an empirical relationship, fitting the experimental data using the selected fitting method, obtaining an empirical relationship between the battery cell performance parameters and the input variables, and obtaining a polynomial relationship between the battery cell voltage and the charge / discharge current and temperature through polynomial fitting;

[0038] S910: Verification and optimization: Apply the established empirical model to simulation calculations, compare and verify it with the test data of actual battery cells, and optimize the model based on the verification results, such as adjusting fitting parameters, adding or changing fitting methods, etc., to improve the accuracy of the model.

[0039] Compared with the prior art, the present invention provides a method for establishing a cell equivalent model for simulation calculation in an energy storage system, which has the following beneficial effects:

[0040] This method for establishing an equivalent model of battery cells for simulation calculations in energy storage systems can better understand and analyze the overall performance of multiple battery cells combined. Through the equivalent model, the performance of the energy storage system can be accurately predicted during the design phase, which helps to optimize the structure and parameters of the system and improve the overall performance and economy of the system. It also provides a powerful tool for the research and development of new energy storage batteries. Researchers can use the equivalent model to simulate different design schemes and working conditions and quickly evaluate their performance, thereby accelerating the research and development process and promoting the innovative development of energy storage technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a model diagram of the present invention;

[0042] Figure 2 It is a simulation result diagram of the present invention. DETAILED DESCRIPTION

[0043] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0044] Embodiment 1:

[0045] like Figure 1-Figure 2 As shown, a method for establishing a cell equivalent model for simulation calculation in an energy storage system includes the following establishment steps:

[0046] S1: Based on electrochemical theory, the electrochemical reactions and ion transport processes inside lithium-ion batteries are determined and described. The space of lithium-ion battery cells is divided into different regions, and corresponding equations are established for each region to describe the physical and chemical processes inside. The materials of lithium-ion batteries include aluminum foil, positive electrode material, copper foil, graphite, diaphragm, electrolyte and lead plastic film. The derivation of the elastic modulus can be known from Formula 1: V f +V m =1;

[0047] Formula 2 shows that horizontal: σ1=σ f V f +σ m V m ;

[0048] Formula 3 shows that vertical: σ2=E f ε f =E m ε m =E2ε2;

[0049]

[0050] Formula 4, ε2 = ε f V f +ε m V m ;

[0051] From formula 1, we can get:

[0052] This leads to Formula 5: E1=E f V f +E m V m ;

[0053] From formula 2 and formula 4, we can know that:

[0054] This leads to Formula 6:

[0055] Let V f and V m is the member f, m is the single phase, which represents the volume fraction percentage of the entire composite material, E f and E m They are respectively expressed as the elastic modulus of components f and m;

[0056] S2: Derivation of Poisson's ratio: When the single layer material is ε1, the lateral strain ε2 = -U 21 ε1, the longitudinal strain of the parallel model is ε1, but there must be the same lateral contraction, and the static equilibrium condition is:

[0057] Formula 7: Vertical, σ f V f =σ m V m ;

[0058] And because, Formula 8:

[0059] Formula 9:

[0060] So we get formula 10:

[0061] S3: The volume fraction, mass fraction and mechanical parameters of lithium-ion battery materials used in energy storage systems are counted and calculated according to the formula, where Formula 11: E x =E y =∑V i E i ;

[0062] Formula 11:

[0063] Formula 12:

[0064] Formula 13: u xz =u yz =∑V i u i ;

[0065] S4: Establish parameters of orthogonal anisotropic materials based on the data obtained in S1-S3 and assign them to the model;

[0066] S5: Solve a set of partial differential equations obtained by the above steps by numerical methods, so as to obtain the changes of parameters such as voltage, current, temperature, etc. of the battery cell under different working conditions;

[0067] S6: Determine the circuit topology structure, and select a suitable equivalent circuit topology structure according to the characteristics of the lithium-ion battery cell and the simulation requirements, including but not limited to the Thevenin model and the RC model. Preferably, the Thevenin model is selected. The Thevenin model consists of an ideal voltage source, which represents the open circuit voltage of the battery cell; a series resistor, which represents the internal resistance of the battery cell; and an RC parallel circuit, which is used to simulate the dynamic characteristics of the battery cell.

[0068] S7: Parameter identification and determination: Experimentally test the voltage and current data of lithium-ion battery cells under different charging and discharging conditions, measure the terminal voltage drop of the battery cells under different discharge currents to determine the value of the series resistance, and analyze the voltage response of the battery cells during pulse charging and discharging to determine the capacitance and resistance values ​​in the RC parallel circuit;

[0069] S8: Model verification and adjustment: Apply the established model to simulation calculations and compare and verify it with the test data of the actual battery cells. If there is a large deviation, the parameters or topology of the model need to be adjusted until the model can accurately simulate the actual behavior of the battery cells.

[0070] S9: After establishing the empirical model, verify it to complete the establishment of the battery cell equivalent model, including the following steps:

[0071] S901: Collect experimental data, conduct a large number of battery cell charge and discharge experiments, and record the performance parameters of the battery cells under different working conditions, such as voltage, capacity, internal resistance, etc. The working conditions include but are not limited to different charge and discharge currents, different temperatures, and different states of charge;

[0072] S902: Select a fitting method. According to the characteristics of the experimental data and the characteristics of the battery cell to be simulated, select an appropriate mathematical fitting method, including but not limited to polynomial fitting, exponential fitting, and logarithmic fitting. When it is found that the voltage of the battery cell shows an approximately linear relationship with the change of the charge and discharge current, a linear fitting method is used.

[0073] S903: Establishing an empirical relationship, fitting the experimental data using the selected fitting method, obtaining an empirical relationship between the battery cell performance parameters and the input variables, and obtaining a polynomial relationship between the battery cell voltage and the charge / discharge current and temperature through polynomial fitting;

[0074] S910: Verification and optimization: Apply the established empirical model to simulation calculations, compare and verify it with the test data of actual battery cells, and optimize the model based on the verification results, such as adjusting fitting parameters, adding or changing fitting methods, etc., to improve the accuracy of the model.

[0075] Embodiment 2:

[0076] A method for establishing a cell equivalent model for simulation calculation in an energy storage system includes the following establishing steps:

[0077] S1: Based on electrochemical theory, the electrochemical reactions and ion transport processes inside lithium-ion batteries are determined and described. The space of lithium-ion battery cells is divided into different regions, and corresponding equations are established for each region to describe the physical and chemical processes inside. The materials of lithium-ion batteries include aluminum foil, positive electrode material, copper foil, graphite, diaphragm, electrolyte and lead plastic film. The derivation of the elastic modulus can be known from Formula 1: V f +V m =1;

[0078] Formula 2 shows that horizontal: σ1=σ f V f +σ m Vm ;

[0079] Formula 3 shows that vertical: σ2=E f ε f =E m ε m =E2ε2;

[0080]

[0081] Formula 4, ε2 = ε f V f +ε m V m ;

[0082] From formula 1, we can get:

[0083] This leads to Formula 5: E1=E f V f +E m V m ;

[0084] From formula 2 and formula 4, we can know that:

[0085] This leads to Formula 6:

[0086] Let V f and V m is the member f, m is the single phase, which represents the volume fraction percentage of the entire composite material, E f and E m They are respectively expressed as the elastic modulus of components f and m;

[0087] S2: Derivation of Poisson's ratio: When the single layer material is ε1, the lateral strain ε2 = -U 21 ε1, the longitudinal strain of the parallel model is ε1, but there must be the same lateral contraction, and the static equilibrium condition is:

[0088] Formula 7: Vertical, σ f V f =σ m V m ;

[0089] And because, Formula 8:

[0090] Formula 9:

[0091] So we get formula 10:

[0092] S3: Statistics of volume fraction, mass fraction and mechanical parameters of lithium-ion battery materials used in energy storage systems are as follows:

[0093] Volume fraction and mass fraction of each material in a lithium-ion battery:

[0094]

[0095]

[0096] Mechanical parameters of each component material of a lithium-ion battery:

[0097]

[0098] And calculate according to the formula, where Formula 11: E x =E y =∑V i E i =15.08GPa;

[0099] Formula 11:

[0100] Formula 12:

[0101] Formula 13: u xz =u yz =∑V i u i =0.321GPa;

[0102] S4: Establish parameters of orthogonal anisotropic materials based on the data obtained in S1-S3 and assign them to the model;

[0103] S5: Solve a set of partial differential equations obtained by the above steps by numerical methods, so as to obtain the changes of parameters such as voltage, current, temperature, etc. of the battery cell under different working conditions;

[0104] S6: Determine the circuit topology structure, and select a suitable equivalent circuit topology structure according to the characteristics of the lithium-ion battery cell and the simulation requirements, including but not limited to the Thevenin model and the RC model. Preferably, the Thevenin model is selected. The Thevenin model consists of an ideal voltage source, which represents the open circuit voltage of the battery cell; a series resistor, which represents the internal resistance of the battery cell; and an RC parallel circuit, which is used to simulate the dynamic characteristics of the battery cell.

[0105] S7: Parameter identification and determination: Experimentally test the voltage and current data of lithium-ion battery cells under different charging and discharging conditions, measure the terminal voltage drop of the battery cells under different discharge currents to determine the value of the series resistance, and analyze the voltage response of the battery cells during pulse charging and discharging to determine the capacitance and resistance values ​​in the RC parallel circuit;

[0106] S8: Model verification and adjustment: Apply the established model to simulation calculations and compare and verify it with the test data of the actual battery cells. If there is a large deviation, the parameters or topology of the model need to be adjusted until the model can accurately simulate the actual behavior of the battery cells.

[0107] S9: After establishing the empirical model, verify it to complete the establishment of the battery cell equivalent model, including the following steps:

[0108] S901: Collect experimental data, conduct a large number of battery cell charge and discharge experiments, and record the performance parameters of the battery cells under different working conditions, such as voltage, capacity, internal resistance, etc. The working conditions include but are not limited to different charge and discharge currents, different temperatures, and different states of charge;

[0109] S902: Select a fitting method. According to the characteristics of the experimental data and the characteristics of the battery cell to be simulated, select an appropriate mathematical fitting method, including but not limited to polynomial fitting, exponential fitting, and logarithmic fitting. When it is found that the voltage of the battery cell shows an approximately linear relationship with the change of the charge and discharge current, a linear fitting method is used.

[0110] S903: Establishing an empirical relationship, fitting the experimental data using the selected fitting method, obtaining an empirical relationship between the battery cell performance parameters and the input variables, and obtaining a polynomial relationship between the battery cell voltage and the charge / discharge current and temperature through polynomial fitting;

[0111] S910: Verification and optimization: Apply the established empirical model to simulation calculations, compare and verify it with the test data of actual battery cells, and optimize the model based on the verification results, such as adjusting fitting parameters, adding or changing fitting methods, etc., to improve the accuracy of the model.

[0112] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for establishing a cell equivalent model for simulation calculation in an energy storage system, comprising the following establishment steps: S1: Based on electrochemical theory, the electrochemical reactions and ion transport processes inside lithium-ion batteries are determined and described. The space of lithium-ion battery cells is divided into different regions, and corresponding equations are established for each region to describe the physical and chemical processes inside. The elastic modulus is derived from formula 1: V f +V m =1; Formula 2 shows that horizontal: σ1=σ f V f +σ m V m ; Formula 3 shows that vertical: σ2=E f ε f =E m ε m =E2ε2; Formula Four, ε2 = ε f V f + ε m V m ; From formula 1, we can get: This leads to Formula 5: E1 = ε f V f +E m V m ; From formula 2 and formula 4, we can know that: This leads to Formula 6: S2: Derivation of Poisson's ratio: When the single layer material is ε1, the lateral strain ε2 = -U 21 ε1, the longitudinal strain of the parallel model is ε1, but there must be the same lateral contraction, and the static equilibrium condition is: Formula 7: Vertical, σ f V f =σ m V m ; And because, Formula 8: Formula 9: So we get formula 10: S3: Perform volume fraction, mass fraction and mechanical parameters statistics on lithium-ion battery materials used in energy storage systems, and calculate them according to the formula, where Formula 11: E x =E y =∑V i E i ; Formula 11: Formula Twelve: Official thirteenth: u xz =u yz = ∑V i u i ; S4: Establish parameters of orthogonal anisotropic materials based on the data obtained in S1-S3 and assign them to the model; S5: Solve a set of partial differential equations obtained by the above steps by numerical methods, so as to obtain the changes of parameters such as voltage, current, temperature, etc. of the battery cell under different working conditions; S6: Determine the circuit topology structure, and select a suitable equivalent circuit topology structure according to the characteristics of the lithium-ion battery cell and the simulation requirements, including but not limited to the Thevenin model and the RC model. Preferably, the Thevenin model is selected. The Thevenin model consists of an ideal voltage source, which represents the open circuit voltage of the battery cell; a series resistor, which represents the internal resistance of the battery cell; and an RC parallel circuit, which is used to simulate the dynamic characteristics of the battery cell. S7: Parameter identification and determination: Experimentally test the voltage and current data of lithium-ion battery cells under different charging and discharging conditions, measure the terminal voltage drop of the battery cells under different discharge currents to determine the value of the series resistance, and analyze the voltage response of the battery cells during pulse charging and discharging to determine the capacitance and resistance values ​​in the RC parallel circuit; S8: Model verification and adjustment: Apply the established model to simulation calculations and compare and verify it with the test data of the actual battery cells. If there is a large deviation, the parameters or topology of the model need to be adjusted until the model can accurately simulate the actual behavior of the battery cells. S9: After establishing the empirical model, verify it to complete the establishment of the battery cell equivalent model.

2. The method for establishing a cell equivalent model for simulation calculation in an energy storage system according to claim 1, characterized in that: In step S1, V f and V m is the member f, m is the single phase, which represents the volume fraction percentage of the entire composite material, E f and E m Expressed as the elastic modulus of components f and m respectively.

3. The method for establishing a cell equivalent model for simulation calculation in an energy storage system according to claim 1, characterized in that: In step S1, the materials of the lithium-ion battery include aluminum foil, positive electrode material, copper foil, graphite, a separator, an electrolyte and a lead plastic film.

4. The method for establishing a cell equivalent model for simulation calculation in an energy storage system according to claim 1, characterized in that: In step S9, establishing an empirical model includes the following steps: S901: Collect experimental data, conduct a large number of battery cell charge and discharge experiments, and record the performance parameters of the battery cells under different working conditions, such as voltage, capacity, internal resistance, etc. The working conditions include but are not limited to different charge and discharge currents, different temperatures, and different states of charge; S902: Select a fitting method. According to the characteristics of the experimental data and the characteristics of the battery cell to be simulated, select an appropriate mathematical fitting method, including but not limited to polynomial fitting, exponential fitting, and logarithmic fitting. When it is found that the voltage of the battery cell shows an approximately linear relationship with the change of the charge and discharge current, a linear fitting method is used. S903: Establishing an empirical relationship, fitting the experimental data using the selected fitting method, obtaining an empirical relationship between the battery cell performance parameters and the input variables, and obtaining a polynomial relationship between the battery cell voltage and the charge / discharge current and temperature through polynomial fitting; S910: Verification and optimization: Apply the established empirical model to simulation calculations, compare and verify it with the test data of actual battery cells, and optimize the model based on the verification results, such as adjusting fitting parameters, adding or changing fitting methods, etc., to improve the accuracy of the model.

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