Solar thermal management system and method based on performance degradation of energy storage system

Abstract

The invention relates to the technical field of photovoltaic-energy storage systems, in particular to a solar thermal management system and method based on performance degradation of an energy storage system, and the system comprises a multi-objective equation derivation module which is used for a multi-objective equation of the operation cost and carbon emission of the photovoltaic-energy storage system; the constraint condition setting module is used for setting constraint conditions of performance degradation of the energy storage system; the model linearization module is used for performing model linearization based on a piecewise linear function linearization method; the scheduling module is used for formulating a power scheduling plan of the photovoltaic-energy storage system according to the health state of the energy storage system and the optimization target; the method has the beneficial effects that the performance degradation constraint condition of the energy storage system is designed, is converted into linear constraint based on the piecewise linear function linearization method, and is fed back to the energy management method, so that the influence of reduction of the maximum available capacity and the maximum charging and discharging power of the energy storage system on energy management is considered in real time; and a reasonable energy management strategy is formulated.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic-energy storage systems, and in particular to a solar thermal management system and method based on performance degradation of an energy storage system. Background Art

[0002] With the rapid development of renewable energy technology, the photovoltaic-energy storage system formed by the combination of photovoltaic and energy storage systems is considered to be a key way to increase the penetration rate of photovoltaics, promote the construction of intelligent power grids and optimize the energy supply structure. However, as the core technology to achieve the above goals, energy management in photovoltaic-energy storage systems faces multiple challenges such as performance degradation of energy storage systems during operation and complex and diverse system optimization objectives, which poses great challenges to the safe operation of photovoltaic-energy storage systems. Therefore, it is urgent to carry out research on multi-objective energy management methods for photovoltaic-energy storage systems under conditions of energy storage system performance degradation to provide guarantee for the safe operation of the system.

[0003] At present, many scholars have conducted extensive research on the energy management optimization problem of photovoltaic-energy storage systems from three aspects: optimization objectives, sources of decision data, and optimization algorithms. However, there are still some shortcomings. On the one hand, existing research has failed to achieve multiple optimizations of operating costs, carbon emissions, and performance degradation of energy storage systems. On the other hand, existing research has not yet considered the impact of energy storage system performance degradation (such as the reduction of maximum available capacity, the reduction of maximum charging and discharging power, etc.) on energy management in real time in the optimization algorithm, nor has it analyzed how to extend the service life of the energy storage system based on this. This will cause the system to exceed its existing maximum capacity or safety range when charging and discharging, posing great challenges to the safe operation of photovoltaic-energy storage systems. Summary of the invention

[0004] The object of the present invention is to provide a solar thermal management system and method based on performance degradation of an energy storage system to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a solar thermal management system based on performance degradation of an energy storage system, the system comprising: Multi-objective equation derivation module, used for multi-objective equations of photovoltaic-energy storage system operation cost and carbon emissions; A constraint condition setting module, used to set the constraint conditions for performance degradation of the energy storage system; Model linearization module, used for model linearization based on piecewise linear function linearization method; The scheduling module is used to formulate a power scheduling plan for the photovoltaic-energy storage system based on the health status of the energy storage system and the optimization objectives.

[0006] Preferably, the multi-objective equation derivation module constructs a system operation cost objective function, and its calculation formula is as follows: ————————(1) In the formula, represents the operating cost of the photovoltaic-energy storage system, T represents the scheduling period, express t The electricity purchase price at the time, express t The exchange power between the photovoltaic-energy storage system and the grid at any moment, Indicates the sampling time interval; In the photovoltaic-energy storage system, carbon emissions come from the electricity purchased from the grid and the output of the photovoltaic power generation system; assuming that all the electricity purchased from the grid is produced from traditional fossil fuel power plants, thus resulting in a large amount of CO2 emissions, the calculation formula is as follows: ——————————————(2) In the formula, Represents the CO2 emissions generated by the electricity purchased by the system from the grid, It represents the CO2 emissions generated by producing 1 kWh of electricity in a traditional fossil fuel power plant; In addition, CO2 emissions are also generated during the production and construction of photovoltaic power generation systems and the transportation of components. The calculation formula is as follows: ——————————(3) In the formula, Represents CO2 emissions generated during the production and construction of photovoltaic power generation systems and the transportation of components. It represents the CO2 emissions generated by the photovoltaic power generation system to produce 1 kWh of electricity. express t The output of photovoltaic power generation system at all times; The carbon emission target equation of the photovoltaic-energy storage system is expressed as: ——————————————(4) In the formula, Represents the total carbon emissions of the PV-storage system; In order to comprehensively consider the operating cost and carbon emissions of the photovoltaic-energy storage system, a multi-objective function equation is constructed based on equations (1) and (4) to obtain the optimal low-carbon economic operation strategy of the system. Its mathematical expression is as follows: ——————————(5) In the formula, Represents the optimization target of the operating cost and carbon emission of the photovoltaic-energy storage system.

[0007] Preferably, the constraint condition setting module includes: (1) State of Charge, SOC upper and lower limit constraints: ——————————————(6) In the formula, Indicates that the energy storage system t SOC at all times, and Respectively represent the upper and lower limits of the SOC of the energy storage system; (2) Charge and discharge power constraints ——————————(7) ————————(8) In the formula, and Respectively represent the energy storage system in t The charging and discharging power at each moment, and Respectively represent the energy storage system in t Maximum charging and discharging power at the moment; (3) SOC conversion constraints before and after

[0008] ————————(9) In the formula, The SOC of the energy storage system at time t, The SOC of the energy storage system at time t-1, represents the actual maximum available capacity of the energy storage system at time t-1, represents the charging efficiency of the energy storage system, represents the discharge efficiency of the energy storage system, is a binary variable, indicating the charging and discharging status of the energy storage system. Indicates the charging status. Indicates the discharge status.

[0009] Preferably, the constraint setting module also includes: According to the definition of State of Health (SOH), the energy storage system t The actual maximum available capacity at the moment , Maximum charging power and maximum discharge power It can be expressed as: ——————————————————(10) ————————(11) ——————(12) In the formula, Indicates the rated capacity of the energy storage system, and Respectively represent the maximum rated charging and discharging power of the energy storage system, Indicates that the energy storage system t The health state at the moment; Substituting equations (10), (11) and (12) into equations (7), (8) and (9), the constraints under the condition of energy storage system performance degradation are obtained: ————————————(13) ——————————(14)

[0010] ————————(15) Comparative analysis of the impact of energy storage system performance degradation on the energy management of photovoltaic-energy storage systems, and the actual maximum available capacity under the condition of ignoring energy storage system performance degradation , Maximum charging power and maximum discharge power The constraint condition is that SOH=100% in equations (13), (14) and (15).

[0011] Preferably, the model linearization module includes: The constraint condition (15) is a nonlinear constraint condition containing binary variables and judgment conditions. It is converted into a linear constraint using Unified representation of the charging and discharging power of the energy storage system, and The relationship can be expressed as: ——————————(16) Then formula (15) can be further expressed as: ——(17) For formula (17), three continuous variables can be used: , and , and 2 0-1 variables and , realize linear transformation; the three continuous variables realize the linearization of formula (17), and the two 0-1 variables limit the values ​​of the three continuous variables, thereby limiting The specific steps are as follows: Find the demarcation point of the piecewise linear function of formula (17). Formula (17) consists of two linear functions, so it has three demarcation points. Let them be in ascending order: , and , its mathematical expression is as follows:

[0012] ——(18) Secondly, the independent variable was replaced by 3 continuous variables and 3 cut-off points. , the replacement formula is as follows: ——————————————(19) Then, the three continuous variables and formula (17) are used to replace the SOC calculation formula, and the calculation formula is as follows: ——————————————(20) Finally, constraints are imposed on the three continuous variables and the two 0-1 variables to limit The constraints in the interval are as follows: --------------(twenty one) ------------------(twenty two) --------------------(twenty three) ----------------(twenty four) ————————————————————(25) The nonlinear constraint (15) is transformed into a linear constraint consisting of (19) to (25) to facilitate the solution of the energy management method of the photovoltaic-energy storage system.

[0013] A solar thermal management method based on energy storage system performance degradation, the method comprising the following steps: Derive the multi-objective equations of the operating cost and carbon emissions of the photovoltaic-energy storage system, so as to achieve dual optimization of operating cost and carbon emissions as the optimization target; Design the performance degradation constraints of the energy storage system and feed them back to the energy management method of the photovoltaic-energy storage system. Adjust the maximum charge and discharge power in real time according to the health status of the energy storage system to solve the unreasonable energy management problem caused by the performance degradation of the energy storage system during the operation of the photovoltaic-energy storage system. Based on the piecewise linear function linearization method, nonlinear constraints are converted into linear constraints, and MINLP problems are converted into MILP problems that are easy to solve, thereby improving the accuracy of solving multi-objective energy management problems. Formulate a power dispatch plan for the photovoltaic-energy storage system based on the health status and optimization objectives of the energy storage system.

[0014] Preferably, the system operation cost objective function is constructed, and its calculation formula is as follows: ————————(1) In the formula, represents the operating cost of the photovoltaic-energy storage system, T represents the scheduling period, express t The electricity purchase price at the time, express t The exchange power between the photovoltaic-energy storage system and the grid at any moment, Indicates the sampling time interval; In the photovoltaic-energy storage system, carbon emissions come from the electricity purchased from the grid and the output of the photovoltaic power generation system; assuming that all the electricity purchased from the grid is produced from traditional fossil fuel power plants, thus resulting in a large amount of CO2 emissions, the calculation formula is as follows: ——————————————(2) In the formula, Represents the CO2 emissions generated by the electricity purchased by the system from the grid, It represents the CO2 emissions generated by producing 1 kWh of electricity in a traditional fossil fuel power plant; In addition, CO2 emissions are also generated during the production and construction of photovoltaic power generation systems and the transportation of components. The calculation formula is as follows: ——————————(3) In the formula, Represents CO2 emissions generated during the production and construction of photovoltaic power generation systems and the transportation of components. It represents the CO2 emissions generated by the photovoltaic power generation system to produce 1 kWh of electricity. express t The output of photovoltaic power generation system at all times; The carbon emission target equation of the photovoltaic-energy storage system is expressed as: ——————————————(4) In the formula, Represents the total carbon emissions of the PV-storage system; In order to comprehensively consider the operating cost and carbon emissions of the photovoltaic-energy storage system, a multi-objective function equation is constructed based on equations (1) and (4) to obtain the optimal low-carbon economic operation strategy of the system. Its mathematical expression is as follows: ——————————(5) In the formula, Represents the optimization target of the operating cost and carbon emission of the photovoltaic-energy storage system.

[0015] Preferably, the constraint condition setting includes: (1) State of Charge, SOC upper and lower limit constraints: ——————————————(6) In the formula, Indicates that the energy storage system t SOC at all times, and Respectively represent the upper and lower limits of the SOC of the energy storage system; (2) Charge and discharge power constraints ——————————(7) ————————(8) In the formula, and Respectively represent the energy storage system in t The charging and discharging power at each moment, and Respectively represent the energy storage system in t Maximum charging and discharging power at the moment; (3) SOC conversion constraints before and after

[0016] ——————(9) In the formula, The SOC of the energy storage system at time t, The SOC of the energy storage system at time t-1, represents the actual maximum available capacity of the energy storage system at time t-1, represents the charging efficiency of the energy storage system, represents the discharge efficiency of the energy storage system, is a binary variable, indicating the charging and discharging status of the energy storage system. Indicates the charging status. Indicates the discharge status.

[0017] Preferably, the constraint setting further includes: According to the definition of State of Health (SOH), the energy storage system t The actual maximum available capacity at the moment , Maximum charging power and maximum discharge power It can be expressed as: ——————————————————(10) ————————(11) ——————(12) In the formula, Indicates the rated capacity of the energy storage system, and Respectively represent the maximum rated charging and discharging power of the energy storage system, Indicates that the energy storage system t The health state at the moment; Substituting equations (10), (11) and (12) into equations (7), (8) and (9), the constraints under the condition of energy storage system performance degradation are obtained: ————————————(13) ——————————(14)

[0018] ————————(15) Comparative analysis of the impact of energy storage system performance degradation on the energy management of photovoltaic-energy storage systems, and the actual maximum available capacity under the condition of ignoring energy storage system performance degradation , Maximum charging power and maximum discharge power The constraint condition is that SOH=100% in equations (13), (14) and (15).

[0019] Preferably, the model linearization includes: The constraint condition (15) is a nonlinear constraint condition containing binary variables and judgment conditions. It is converted into a linear constraint using Unified representation of the charging and discharging power of the energy storage system, and The relationship can be expressed as: ——————————(16) Then formula (15) can be further expressed as: ——(17) For formula (17), three continuous variables can be used: , and , and 2 0-1 variables and , realize linear transformation; the three continuous variables realize the linearization of formula (17), and the two 0-1 variables limit the values ​​of the three continuous variables, thereby limiting The specific steps are as follows: Find the demarcation point of the piecewise linear function of formula (17). Formula (17) consists of two linear functions, so it has three demarcation points. Let them be in ascending order: , and , its mathematical expression is as follows:

[0020] ————(18) Secondly, the independent variable was replaced by 3 continuous variables and 3 cut-off points. , the replacement formula is as follows: ——————————————(19) Then, the three continuous variables and formula (17) are used to replace the SOC calculation formula, and the calculation formula is as follows: ——————————————(20) Finally, constraints are imposed on the three continuous variables and the two 0-1 variables to limit The constraints in the interval are as follows: --------------(twenty one) ------------------(twenty two) --------------------(twenty three) ----------------(twenty four) ————————————————————(25) The nonlinear constraint (15) is transformed into a linear constraint consisting of (19) to (25) to facilitate the solution of the energy management method of the photovoltaic-energy storage system.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The solar thermal management system and method based on the performance degradation of the energy storage system proposed in the present invention designs the performance degradation constraints of the energy storage system, converts them into linear constraints based on the piecewise linear function linearization method, and feeds them back to the energy management method, thereby taking into account in real time the impact of the reduction of the maximum available capacity and the maximum charge and discharge power of the energy storage system on energy management, and formulating a reasonable energy management strategy. This enables the photovoltaic-energy storage system to adjust the maximum charge and discharge power in real time according to the health status of the energy storage system, avoids exceeding its existing maximum capacity or safety range during charging and discharging, and solves the problem of shortened service life of the energy storage system due to unreasonable power allocation. Therefore, this method can solve the problem of unreasonable energy management caused by the performance degradation of the energy storage system during the operation of the photovoltaic-energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart of the method of the present invention; Figure 2 Schematic diagram of electricity price of the photovoltaic-energy storage system of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose and technical solution of the present invention clearly and completely described, and the advantages more clearly understood, the embodiments of the present invention are further described in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Embodiment 1, the present invention provides a technical solution: a solar thermal management system based on performance degradation of an energy storage system, the system comprising: Multi-objective equation derivation module, used for multi-objective equations of photovoltaic-energy storage system operation cost and carbon emissions; The system operation cost objective function is constructed, and its calculation formula is as follows: ————————(1) In the formula, represents the operating cost of the photovoltaic-energy storage system, T represents the scheduling period, express t The electricity purchase price at the time, express t The exchange power between the photovoltaic-energy storage system and the grid at any moment, Indicates the sampling time interval; In the photovoltaic-energy storage system, carbon emissions come from the electricity purchased from the grid and the output of the photovoltaic power generation system; assuming that all the electricity purchased from the grid is produced from traditional fossil fuel power plants, thus resulting in a large amount of CO2 emissions, the calculation formula is as follows: ————————————(2) In the formula, Represents the CO2 emissions generated by the electricity purchased by the system from the grid, It represents the CO2 emissions generated by producing 1 kWh of electricity in a traditional fossil fuel power plant; In addition, CO2 emissions are also generated during the production and construction of photovoltaic power generation systems and the transportation of components. The calculation formula is as follows: ——————————(3) In the formula, Represents CO2 emissions generated during the production and construction of photovoltaic power generation systems and the transportation of components. It represents the CO2 emissions generated by the photovoltaic power generation system to produce 1 kWh of electricity. express t The output of photovoltaic power generation system at all times; The carbon emission target equation of the photovoltaic-energy storage system is expressed as: ——————————————(4) In the formula, represents the total carbon emissions of the photovoltaic-energy storage system; a In order to comprehensively consider the operating cost and carbon emissions of the photovoltaic-energy storage system, a multi-objective function equation is constructed based on equations (1) and (4) to obtain the optimal low-carbon economic operation strategy of the system. Its mathematical expression is as follows: ——————————(5) In the formula, Represents the optimization target of the operating cost and carbon emission of the photovoltaic-energy storage system.

[0024] The constraint condition setting module is used to set the constraint conditions for the performance degradation of the energy storage system; including: (1) State of Charge, SOC upper and lower limit constraints: ——————————————(6) In the formula, Indicates that the energy storage system t SOC at all times, and Respectively represent the upper and lower limits of the SOC of the energy storage system; (2) Charge and discharge power constraints ——————————(7) ————————(8) In the formula, and Respectively represent the energy storage system in t The charging and discharging power at each moment, and Respectively represent the energy storage system in t Maximum charging and discharging power at the moment; (3) SOC conversion constraints before and after

[0025] ————(9) In the formula, The SOC of the energy storage system at time t, The SOC of the energy storage system at time t-1, represents the actual maximum available capacity of the energy storage system at time t-1, represents the charging efficiency of the energy storage system, represents the discharge efficiency of the energy storage system, is a binary variable, indicating the charging and discharging status of the energy storage system. Indicates the charging status. Indicates the discharge status.

[0026] Also includes: According to the definition of State of Health (SOH), the energy storage system t The actual maximum available capacity at the moment , Maximum charging power and maximum discharge power It can be expressed as: ——————————————————(10) ————————(11) ——————(12) In the formula, Indicates the rated capacity of the energy storage system, and Respectively represent the maximum rated charging and discharging power of the energy storage system, Indicates that the energy storage system tThe health state at the moment; Substituting equations (10), (11) and (12) into equations (7), (8) and (9), the constraints under the condition of energy storage system performance degradation are obtained: ————————————(13) ——————————(14)

[0027] ————(15) Comparative analysis of the impact of energy storage system performance degradation on the energy management of photovoltaic-energy storage systems, and the actual maximum available capacity under the condition of ignoring energy storage system performance degradation , Maximum charging power and maximum discharge power The constraint condition is that SOH=100% in equations (13), (14) and (15).

[0028] Model linearization module, used for model linearization based on piecewise linear function linearization method; The scheduling module is used to formulate a power scheduling plan for the photovoltaic-energy storage system based on the health status of the energy storage system and the optimization objectives.

[0029] include: The constraint condition (15) is a nonlinear constraint condition containing binary variables and judgment conditions. It is converted into a linear constraint using Unified representation of the charging and discharging power of the energy storage system, and The relationship can be expressed as: ——————————(16) Then formula (15) can be further expressed as: ——(17) For formula (17), three continuous variables can be used: , and , and 2 0-1 variables and , realize linear transformation; the three continuous variables realize the linearization of formula (17), and the two 0-1 variables limit the values ​​of the three continuous variables, thereby limiting The specific steps are as follows: Find the demarcation point of the piecewise linear function of formula (17). Formula (17) consists of two linear functions, so it has three demarcation points. Let them be in ascending order: , and , its mathematical expression is as follows:

[0030] ——(18) Secondly, the independent variable was replaced by 3 continuous variables and 3 cut-off points. , the replacement formula is as follows: ——————————————(19) Then, the three continuous variables and formula (17) are used to replace the SOC calculation formula, and the calculation formula is as follows: ——————————————(20) Finally, constraints are imposed on the three continuous variables and the two 0-1 variables to limit The constraints in the interval are as follows: --------------(twenty one) ------------------(twenty two) --------------------(twenty three) ----------------(twenty four) ————————————————————(25) The nonlinear constraint (15) is transformed into a linear constraint consisting of (19) to (25) to facilitate the solution of the energy management method of the photovoltaic-energy storage system.

[0031] Embodiment 2, refer to the attached Figure 1 Based on the first embodiment, a solar thermal management method based on energy storage system performance degradation is proposed. The method comprises the following steps: The multi-objective equations of the operating cost and carbon emissions of the photovoltaic-energy storage system are derived, so as to achieve the dual optimization of operating cost and carbon emissions as the optimization target; in order to explore the abandonment rate of the photovoltaic-energy storage system itself, this method constructs the system operating cost objective function under the premise of only purchasing power from the power grid. The calculation formula is as follows: ————————(1) In the formula, represents the operating cost of the photovoltaic-energy storage system, T represents the scheduling period, expresst The electricity purchase price at the time, express t The exchange power between the photovoltaic-energy storage system and the grid at any moment, Indicates the sampling time interval.

[0032] In the photovoltaic-energy storage system, carbon emissions mainly come from the electricity purchased from the grid and the output of the photovoltaic power generation system. This method assumes that all the electricity purchased from the grid is produced from traditional fossil fuel power plants, which will result in a large amount of CO2 emissions. The calculation formula is as follows: ——————————————(2) In the formula, Represents the CO2 emissions generated by the electricity purchased by the system from the grid, Represents the CO2 emissions generated by a traditional fossil fuel power plant producing 1 kWh of electricity.

[0033] In addition, the production and construction of photovoltaic power generation systems and the transportation of components will also generate CO2 emissions. The calculation formula is as follows: ——————————(3) In the formula, Represents CO2 emissions generated during the production and construction of photovoltaic power generation systems and the transportation of components. It represents the CO2 emissions generated by the photovoltaic power generation system to produce 1 kWh of electricity. express t The output of the photovoltaic power generation system at all times.

[0034] Therefore, the carbon emission target equation of the photovoltaic-energy storage system can be expressed as: ——————————————(4) In the formula, Represents the total carbon emissions of the PV-storage system; In order to comprehensively consider the operating cost and carbon emissions of the photovoltaic-energy storage system, this method constructs a multi-objective function equation based on equations (1) and (4) to obtain the optimal low-carbon economic operation strategy of the system. Its mathematical expression is as follows: ——————————(5) In the formula, Represents the optimization target of the operating cost and carbon emission of the photovoltaic-energy storage system.

[0035] Design the performance degradation constraints of the energy storage system and feed them back to the energy management method of the photovoltaic-energy storage system. Adjust the maximum charge and discharge power in real time according to the health status of the energy storage system to solve the unreasonable energy management problem caused by the performance degradation of the energy storage system during the operation of the photovoltaic-energy storage system; (1) State of Charge (SOC) upper and lower line constraints ————————————————(6) In the formula, Indicates that the energy storage system t SOC at all times, and They represent the upper and lower limits of the SOC of the energy storage system respectively.

[0036] (2) Charge and discharge power constraints ——————————(7) ————————(8) In the formula, and Respectively represent the energy storage system in t The charging and discharging power at each moment, and Respectively represent the energy storage system in t The maximum charge and discharge power at the moment.

[0037] (3) SOC conversion constraints before and after

[0038] ————(9) In the formula, The SOC of the energy storage system at time t, The SOC of the energy storage system at time t-1, represents the actual maximum available capacity of the energy storage system at time t-1, represents the charging efficiency of the energy storage system, represents the discharge efficiency of the energy storage system, is a binary variable, indicating the charging and discharging status of the energy storage system. Indicates the charging status. Indicates the discharge status.

[0039] Furthermore, this method takes the performance degradation of the energy storage system during operation as a constraint condition so that the established energy management method can take into account the impact of the reduction of the maximum available capacity and maximum charging and discharging power of the energy storage system on the energy management of the photovoltaic-energy storage system. According to the definition of State of Health (SOH), the energy storage system is t The actual maximum available capacity at the moment , Maximum charging power and maximum discharge power It can be expressed as: ——————————————————(10) ————————(11) ——————(12) In the formula, Indicates the rated capacity of the energy storage system, and Respectively represent the maximum rated charging and discharging power of the energy storage system, Indicates that the energy storage system t Health status at all times.

[0040] Furthermore, by substituting equations (10), (11) and (12) into equations (7), (8) and (9), we can obtain the constraints under the condition of energy storage system performance degradation.

[0041] ————————————(13) ——————————(14)

[0042] ——————(15) Comparative analysis of the impact of energy storage system performance degradation on the energy management of photovoltaic-energy storage systems, and the actual maximum available capacity under the condition of ignoring energy storage system performance degradation , Maximum charging power and maximum discharge power The constraint condition is that SOH=100% in equations (13), (14) and (15).

[0043] Based on the piecewise linear function linearization method, nonlinear constraints are converted into linear constraints, and the MINLP problem is converted into an easy-to-solve MILP problem, which improves the solution accuracy of the multi-objective energy management problem. The constraint condition (15) is a nonlinear constraint condition containing binary variables and judgment conditions. In order to convert it into a linear constraint, this paper uses Unified representation of the charging and discharging power of the energy storage system, and The relationship can be expressed as: ——————————(16) Then formula (15) can be further expressed as: ——(17) For formula (17), three continuous variables can be used: , and , and 2 0-1 variables and , to achieve linear transformation. The three continuous variables realize the linearization of formula (17), and the two 0-1 variables limit the values ​​of the three continuous variables, thereby limiting The specific steps are as follows: First, find the demarcation point of the piecewise linear function of equation (17). Equation (17) consists of two linear functions, so it has three demarcation points, which are set in ascending order as follows: , and . Its mathematical expression is as follows:

[0044] ————(18) Secondly, the independent variable was replaced by 3 continuous variables and 3 cut-off points. , the replacement formula is as follows: ——————————————(19) Then, the three continuous variables and formula (17) are used to replace the SOC calculation formula, and the calculation formula is as follows: ——————————————(20) Finally, constraints are imposed on the three continuous variables and the two 0-1 variables to limit The constraints are as follows: --------------(twenty one) ------------------(twenty two) --------------------(twenty three) ----------------(twenty four) ————————————————————(25) It can be seen that the nonlinear constraint (15) can be transformed into a linear constraint consisting of (19) to (25) to facilitate the solution of the energy management method of the photovoltaic-energy storage system.

[0045] Formulate a power dispatch plan for the photovoltaic-energy storage system based on the health status and optimization objectives of the energy storage system.

[0046] Embodiment 3, based on embodiment 2, proposes the following embodiment: The experimental data comes from the California Integrated Energy System Dataset, USA, and is used for a multi-objective energy management method that considers the performance degradation of the energy storage system under the volt-storage system. In addition, in order to verify the effectiveness of this method, seven scenarios are set up according to whether the performance degradation of the energy storage system, carbon emissions and operating costs are considered, and whether the energy storage system is configured: (1) No energy storage system is configured; (2) Considering carbon emissions; (3) Considering operating costs; (4) Considering carbon emissions and operating costs; (5) Considering carbon emissions and energy storage system performance degradation; (6) Considering operating costs and energy storage system performance degradation; (7) Considering carbon emissions, operating costs and energy storage system performance degradation, that is, the method proposed in this patent.

[0047] In order to simulate the operation of the system, the relevant parameters of the photovoltaic-energy storage system are given in Table 1. Figure 2 Shows the evolution of system electricity prices over time.

[0048] Table 1 The performance results of this patented technology on test data

[0049] Table 2 shows the carbon emissions, abandoned light rate and operating costs of the patented technology on the test data. It can be seen that the method proposed in this patent can make carbon emissions close to the energy management method with carbon emissions as the target, and at the same time make the operating cost close to the energy management method with operating costs as the target. Therefore, the patented technology can comprehensively consider the advantages of both, thereby achieving dual optimization of carbon emissions and operating costs. In addition, after considering the performance degradation of the energy storage system, the system carbon emissions, abandoned light rate and operating costs have increased. This is because the performance degradation of the energy storage system has reduced its available capacity and reduced its time and space transfer capacity. Further, Table 3 shows the service life of the energy storage system on the test data of the patented technology. The analysis shows that the energy storage system of the patented technology has the longest service life, reaching 1887 days, which is 94 days longer than the multi-objective optimization energy management method that does not consider the performance degradation of the energy storage system. In addition, after considering the performance degradation of the energy storage system, the service life of the energy storage system in all scenarios has increased significantly. Among them, the service life of the energy management method with operating costs as the target has increased by 98 days, while the service life of the energy management method with carbon emissions as the target has increased by 223 days. This is because incorporating the performance degradation of the energy storage system as a constraint condition into the energy management method established by this patent can provide real and reliable degradation status information of the energy storage system for the formulation of energy management strategies, avoiding the use capacity and charging and discharging speed that exceed the battery's tolerance during long-term use, thereby extending its service life.

[0050] In summary, the method proposed in this patent can not only achieve dual optimization of the operating cost and carbon emissions of the photovoltaic-energy storage system, but also adjust the maximum charging and discharging power in real time according to the health status of the energy storage system, solve the problem of unreasonable energy management caused by the performance degradation of the energy storage system during operation, and effectively extend the service life of the energy storage system.

[0051] Table 2 Carbon emissions, abandoned light rate and operating costs of this patented technology based on test data

[0052] Table 3 The service life of the energy storage system based on the test data of this patented technology

[0053] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A solar thermal management system based on energy storage system performance degradation, characterized in that: The system comprises: Multi-objective equation derivation module, used for multi-objective equations of photovoltaic-energy storage system operation cost and carbon emissions; A constraint condition setting module, used to set the constraint conditions for performance degradation of the energy storage system; Model linearization module, used for model linearization based on piecewise linear function linearization method; The scheduling module is used to formulate a power scheduling plan for the photovoltaic-energy storage system based on the health status of the energy storage system and the optimization objectives.

2. A solar thermal management system based on energy storage system performance degradation according to claim 1, characterized in that: The multi-objective equation derivation module constructs the system operation cost objective function, and its calculation formula is as follows: ————————(1) In the formula, represents the operating cost of the photovoltaic-energy storage system, T represents the scheduling period, express t The electricity purchase price at the time, express t The exchange power between the photovoltaic-energy storage system and the grid at any moment, Indicates the sampling time interval; In the photovoltaic-energy storage system, carbon emissions come from the electricity purchased from the grid and the output of the photovoltaic power generation system; assuming that all the electricity purchased from the grid is produced from traditional fossil fuel power plants, thus resulting in a large amount of CO2 emissions, the calculation formula is as follows: ——————————————(2) In the formula, Represents the CO2 emissions generated by the electricity purchased by the system from the grid, It represents the CO2 emissions generated by producing 1 kWh of electricity in a traditional fossil fuel power plant; In addition, CO2 emissions are also generated during the production and construction of photovoltaic power generation systems and the transportation of components. The calculation formula is as follows: ——————————(3) In the formula, Represents the CO2 emissions generated during the production and construction of photovoltaic power generation systems and the transportation of components. It represents the CO2 emissions generated by the photovoltaic power generation system to produce 1 kWh of electricity. express t The output of photovoltaic power generation system at all times; The carbon emission target equation of the photovoltaic-energy storage system is expressed as: ——————————————(4) In the formula, Represents the total carbon emissions of the PV-storage system; In order to comprehensively consider the operating cost and carbon emissions of the photovoltaic-energy storage system, a multi-objective function equation is constructed based on equations (1) and (4) to obtain the optimal low-carbon economic operation strategy of the system. Its mathematical expression is as follows: ——————————(5) In the formula, Represents the optimization target of the operating cost and carbon emission of the photovoltaic-energy storage system.

3. A solar thermal management system based on energy storage system performance degradation according to claim 1, characterized in that: The constraint condition setting module includes: (1) State of Charge, SOC upper and lower limit constraints: ——————————————(6) In the formula, Indicates that the energy storage system t SOC at all times, and Respectively represent the upper and lower limits of the SOC of the energy storage system; (2) Charge and discharge power constraints ——————————(7) ————————(8) In the formula, and Respectively represent the energy storage system in t The charging and discharging power at each moment, and Respectively represent the energy storage system in t Maximum charging and discharging power at the moment; (3) SOC conversion constraints before and after ——————(9) In the formula, The SOC of the energy storage system at time t, The SOC of the energy storage system at time t-1, represents the actual maximum available capacity of the energy storage system at time t-1, represents the charging efficiency of the energy storage system, represents the discharge efficiency of the energy storage system, is a binary variable, indicating the charging and discharging status of the energy storage system. Indicates the charging status. Indicates the discharge status.

4. A solar thermal management system based on energy storage system performance degradation according to claim 3, characterized in that: The constraint setting module also includes: According to the definition of State of Health (SOH), the energy storage system t The actual maximum available capacity at the moment , Maximum charging power and maximum discharge power It can be expressed as: ——————————————————(10) ————————(11) ——————(12) In the formula, Indicates the rated capacity of the energy storage system, and Respectively represent the maximum rated charging and discharging power of the energy storage system, Indicates that the energy storage system t The health state at the moment; Substituting equations (10), (11) and (12) into equations (7), (8) and (9), the constraints under the condition of energy storage system performance degradation are obtained: ————————————(13) ——————————(14) ——————(15) Comparative analysis of the impact of energy storage system performance degradation on the energy management of photovoltaic-energy storage systems, and the actual maximum available capacity under the condition of ignoring energy storage system performance degradation , Maximum charging power and maximum discharge power The constraint condition is that SOH=100% in equations (13), (14) and (15).

5. A solar thermal management system based on energy storage system performance degradation according to claim 1, characterized in that: The model linearization module includes: The constraint condition (15) is a nonlinear constraint condition containing binary variables and judgment conditions. It is converted into a linear constraint using Unified representation of the charging and discharging power of the energy storage system, and The relationship can be expressed as: ——————————(16) Then formula (15) can be further expressed as: ——(17) For formula (17), three continuous variables can be used: , and , and 2 0-1 variables and , realize linear transformation; the three continuous variables realize the linearization of formula (17), and the two 0-1 variables limit the values ​​of the three continuous variables, thereby limiting The specific steps are as follows: Find the demarcation point of the piecewise linear function of formula (17). Formula (17) consists of two linear functions, so it has three demarcation points. Let them be in ascending order: , and , its mathematical expression is as follows: ————(18) Secondly, the independent variable was replaced by 3 continuous variables and 3 cut-off points. , the replacement formula is as follows: ——————————————(19) Then, the three continuous variables and formula (17) are used to replace the SOC calculation formula, and the calculation formula is as follows: ——————————————(20) Finally, constraints are imposed on the three continuous variables and the two 0-1 variables to limit The constraints in the interval are as follows: ——————————————(21) ——————————————————(22) ————————————————————(23) ————————————————(24) ————————————————————(25) The nonlinear constraint (15) is transformed into a linear constraint consisting of (19) to (25) to facilitate the solution of the energy management method of the photovoltaic-energy storage system.

6. A solar thermal management method based on energy storage system performance degradation, using the solar thermal management system based on energy storage system performance degradation according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: Derive the multi-objective equations of the operating cost and carbon emissions of the photovoltaic-energy storage system, so as to achieve dual optimization of operating cost and carbon emissions as the optimization target; Design the performance degradation constraints of the energy storage system and feed them back to the energy management method of the photovoltaic-energy storage system. Adjust the maximum charge and discharge power in real time according to the health status of the energy storage system to solve the unreasonable energy management problem caused by the performance degradation of the energy storage system during the operation of the photovoltaic-energy storage system. Based on the piecewise linear function linearization method, nonlinear constraints are converted into linear constraints, and MINLP problems are converted into MILP problems that are easy to solve, thereby improving the accuracy of solving multi-objective energy management problems. Formulate a power dispatch plan for the photovoltaic-energy storage system based on the health status and optimization objectives of the energy storage system.

7. A solar thermal management method based on energy storage system performance degradation according to claim 6, characterized in that: The system operation cost objective function is constructed, and its calculation formula is as follows: ————————(1) In the formula, represents the operating cost of the photovoltaic-energy storage system, T represents the scheduling period, express t The electricity purchase price at the time, express t The exchange power between the photovoltaic-energy storage system and the grid at any moment, Indicates the sampling time interval; In the photovoltaic-energy storage system, carbon emissions come from the electricity purchased from the grid and the output of the photovoltaic power generation system; assuming that all the electricity purchased from the grid is produced from traditional fossil fuel power plants, thus resulting in a large amount of CO2 emissions, the calculation formula is as follows: ——————————————(2) In the formula, Represents the CO2 emissions generated by the electricity purchased by the system from the grid, It represents the CO2 emissions generated by producing 1 kWh of electricity in a traditional fossil fuel power plant; In addition, CO2 emissions are also generated during the production and construction of photovoltaic power generation systems and the transportation of components. The calculation formula is as follows: ———————————(3) In the formula, Represents CO2 emissions generated during the production and construction of photovoltaic power generation systems and the transportation of components. It represents the CO2 emissions generated by the photovoltaic power generation system to produce 1 kWh of electricity. express t The output of photovoltaic power generation system at all times; The carbon emission target equation of the photovoltaic-energy storage system is expressed as: ————————(4) In the formula, Represents the total carbon emissions of the PV-storage system; In order to comprehensively consider the operating cost and carbon emissions of the photovoltaic-energy storage system, a multi-objective function equation is constructed based on equations (1) and (4) to obtain the optimal low-carbon economic operation strategy of the system. Its mathematical expression is as follows: ——————————(5) In the formula, Represents the optimization target of the operating cost and carbon emission of the photovoltaic-energy storage system.

8. A solar thermal management method based on energy storage system performance degradation according to claim 7, characterized in that: Constraint settings include: (1) State of Charge, SOC upper and lower limit constraints: ——————————————(6) In the formula, Indicates that the energy storage system t SOC at all times, and Respectively represent the upper and lower limits of the SOC of the energy storage system; (2) Charge and discharge power constraints ——————————(7) ————————(8) In the formula, and Respectively represent the energy storage system in t The charging and discharging power at each moment, and Respectively represent the energy storage system in t Maximum charging and discharging power at the moment; (3) SOC conversion constraints before and after ——————(9) In the formula, The SOC of the energy storage system at time t, The SOC of the energy storage system at time t-1, represents the actual maximum available capacity of the energy storage system at time t-1, represents the charging efficiency of the energy storage system, represents the discharge efficiency of the energy storage system, is a binary variable, indicating the charging and discharging status of the energy storage system. Indicates the charging status. Indicates the discharge status.

9. A solar thermal management method based on energy storage system performance degradation according to claim 8, characterized in that: The constraint setting also includes: According to the definition of State of Health (SOH), the energy storage system t The actual maximum available capacity at the moment , Maximum charging power and maximum discharge power It can be expressed as: ——————————————————(10) ————————(11) ——————(12) In the formula, Indicates the rated capacity of the energy storage system, and Respectively represent the maximum rated charging and discharging power of the energy storage system, Indicates that the energy storage system t The health state at the moment; Substituting equations (10), (11) and (12) into equations (7), (8) and (9), the constraints under the condition of energy storage system performance degradation are obtained: ————————————(13) ——————————(14) ——————(15) Comparative analysis of the impact of energy storage system performance degradation on the energy management of photovoltaic-energy storage systems, and the actual maximum available capacity under the condition of ignoring energy storage system performance degradation , Maximum charging power and maximum discharge power The constraint condition is that SOH=100% in equations (13), (14) and (15).

10. A solar thermal management method based on energy storage system performance degradation according to claim 9, characterized in that: Model linearization includes: The constraint condition (15) is a nonlinear constraint condition containing binary variables and judgment conditions. It is converted into a linear constraint using Unified representation of the charging and discharging power of the energy storage system, and The relationship can be expressed as: ——————————(16) Then formula (15) can be further expressed as: (17) For formula (17), three continuous variables can be used: , and , and 2 0-1 variables and , realize linear transformation; the three continuous variables realize the linearization of formula (17), and the two 0-1 variables limit the values ​​of the three continuous variables, thereby limiting The specific steps are as follows: Find the demarcation point of the piecewise linear function of formula (17). Formula (17) consists of two linear functions, so it has three demarcation points. Let them be in ascending order: , and , its mathematical expression is as follows: ————(18) Secondly, the independent variable was replaced by 3 continuous variables and 3 cut-off points. , the replacement formula is as follows: ——————————————(19) Then, the three continuous variables and formula (17) are used to replace the SOC calculation formula, and the calculation formula is as follows: ——————————————(20) Finally, constraints are imposed on the three continuous variables and the two 0-1 variables to limit The constraints in the interval are as follows: ——————————————(21) ——————————————————(22) ————————————————————(23) ————————————————(24) ————————————————————(25) The nonlinear constraint (15) is transformed into a linear constraint consisting of (19) to (25) to facilitate the solution of the energy management method of the photovoltaic-energy storage system.

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