A hybrid energy storage control system for power grid frequency regulation

Abstract

A hybrid energy storage control system for power grid frequency modulation includes a coordination controller, a power storage converter (PCS), a super capacitor subsystem, and a lithium electronic system; the coordination controller includes a coordination controller data terminal and a coordination controller control terminal, the coordination controller data terminal is responsible for collecting, processing and analyzing real-time data, and providing decision support, the coordination controller control terminal is responsible for executing the charging and discharging strategy generated by the optimization algorithm, and controlling the operation of each energy storage unit, the energy storage converter is responsible for the conversion and transmission of electric energy, and realizes the energy exchange between the energy storage system and the power grid, the super capacitor subsystem provides instantaneous high-power output, smoothing power grid fluctuations and assisting power grid frequency modulation, and the lithium electronic system is used for power grid peak regulation, backup power supply and smooth output of renewable energy. The present invention effectively copes with the frequency fluctuation problem caused by the access of renewable energy by improving the speed and accuracy of power grid frequency modulation, and improves the reliability and stability of the power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of power system frequency regulation, and in particular to a hybrid energy storage control system for power grid frequency regulation. Background Art

[0002] The technical background of the present invention is based on the development needs of the current power system and energy storage technology, especially when renewable energy is widely connected to the power grid, the stability and flexibility of the power grid become key issues. With the growing global demand for clean energy, the proportion of renewable energy such as wind energy and solar energy has increased rapidly, but the intermittent and volatile nature of these energy sources has also brought new challenges to the stable operation of the power system. Traditional power grid frequency regulation technology mainly relies on large-scale thermal power generation and hydropower generating units to maintain the stability of the power grid frequency by adjusting the output power of these units. However, the regulation speed and flexibility of traditional units are limited, and they cannot quickly respond to rapid changes in frequency in the power grid, especially when a high proportion of renewable energy is connected, the frequency regulation capability is particularly insufficient.

[0003] In order to deal with this problem, energy storage technology has become one of the important means of grid frequency regulation. The energy storage system can respond quickly when the grid frequency fluctuates and provide the required power support, thereby effectively stabilizing the grid frequency. At present, there are many energy storage technologies on the market that have been applied to grid frequency regulation. Among them, lithium-ion batteries are widely used in long-term energy balance due to their high energy density and long cycle life. However, the power density of lithium-ion batteries is relatively low, and it is difficult to respond quickly to drastic frequency fluctuations. In contrast, supercapacitors have the characteristics of high power density and fast response, which are very suitable for high-frequency regulation on a short time scale, but their energy density is low and they cannot maintain long-term power output.

[0004] In this context, hybrid energy storage systems have emerged, combining supercapacitors and lithium-ion batteries to form an energy storage system that can be efficiently adjusted on different time scales. This hybrid energy storage system can use supercapacitors to quickly respond to frequency fluctuations in a short period of time, while relying on lithium-ion batteries for energy balance over a longer period of time, thereby achieving all-round regulation of grid frequency.

[0005] However, despite the significant advantages of hybrid energy storage systems, they still face many challenges in practical applications. First, the coordinated control and energy management of different energy storage components is a complex process, and it is necessary to develop efficient control strategies to give full play to the advantages of each energy storage unit. Secondly, the thermal management of energy storage systems is also an important issue, especially in high power density application scenarios, where battery temperature control directly affects its life and safety. Therefore, how to achieve optimal control of hybrid energy storage systems in a complex power system environment has become a research focus. Summary of the invention

[0006] In view of the above problems, the present invention aims to provide a hybrid energy storage control system for grid frequency regulation to solve the problems raised in the above background technology.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A hybrid energy storage control system for power grid frequency modulation includes a coordination controller, a power storage converter (PCS), a supercapacitor subsystem, and a lithium electronic system; the coordination controller includes a coordination controller data terminal and a coordination controller control terminal, the coordination controller data terminal is responsible for collecting, processing and analyzing real-time data and providing decision support, the coordination controller control terminal is responsible for executing the charging and discharging strategy generated by the optimization algorithm and controlling the operation of each energy storage unit, the energy storage converter is responsible for the conversion and transmission of electric energy and realizes the energy exchange between the energy storage system and the power grid, the supercapacitor subsystem provides instantaneous high-power output, smoothes power grid fluctuations and assists in power grid frequency modulation, and the lithium electronic system is used for power grid peak regulation, backup power supply and smooth output of renewable energy.

[0009] Furthermore, the coordination controller comprehensively monitors, analyzes and controls the entire system to ensure that the energy storage system can accurately dispatch energy according to the demand and status of the power grid. The coordination controller includes a coordination controller data end and a coordination controller control end. The coordination controller data end cleans, filters and converts the collected data to eliminate noise and outliers to ensure the accuracy and reliability of the data. It can estimate the state of the energy storage system in real time. The estimation result provides a basis for the system's predictive analysis, so that the coordination controller can predict the needs of the power grid and formulate corresponding charging and discharging strategies. The coordination controller control end can dynamically adjust the charging and discharging power of the energy storage system according to the analysis results provided by the coordination controller data end to ensure that the system can operate in the best state under different working conditions. The coordination controller control end has real-time monitoring and dynamic adjustment capabilities. Through the feedback control mechanism, the coordination controller can quickly adjust the operating state of the energy storage system when the power grid frequency fluctuates, provide rapid response, and maintain the stability of the power grid.

[0010] Furthermore, the coordination controller data end includes a data acquisition unit, a data processing unit, a state estimation unit, a prediction analysis unit, and a decision support unit. The data acquisition unit collects voltage, current, frequency, temperature, and remaining power data of the power grid and the energy storage system in real time. The data processing unit performs data cleaning, filtering, and format conversion on the collected data, removes noise and outliers through data cleaning, smoothes the data using a low-pass filter method, eliminates high-frequency noise, and de-dimensionalizes the data, so that the data eliminates the statistical differences caused by the dimensions and completes the format conversion; the state estimation unit estimates the current state of the energy storage system based on real-time data and mathematical models, and establishes a state estimation model:

[0011]

[0012]

[0013]

[0014] in, Predict the state of the data at step k, Update the state for the data in step k-1, μ k-1 is the control quantity of the system in the k-1th step, A, B, C are system matrices, Update the state of the data in step k, P k-1|k-1 is the updated prediction error covariance of the k-1th step, P k|k is the updated prediction error covariance at step k, z k are data observations, σ and is the Gaussian variance, GAUSS(0,σ) represents a Gaussian function with a mean of 0 and a variance of σ, cov is the covariance function, I is the unit matrix, and the prediction analysis unit records the data update state matrix as X, holds, where α and β are constants, p is the autoregressive order, q is the moving average order, φ is the autoregressive coefficient, and θ j is the moving average coefficient, ε(k) is the error term of the kth step, and the decision support unit combines the state estimation and prediction analysis results to generate the charging and discharging strategy of the energy storage system.

[0015] Furthermore, the control end of the coordination controller includes a strategy execution unit, a real-time monitoring unit, a dynamic adjustment unit, and a fault management unit. The strategy execution unit receives and executes the charging and discharging strategy generated by the optimization algorithm to control the operating status of the energy storage device. The real-time monitoring unit monitors the real-time operating status of the power grid and the energy storage system to ensure that the system operates within a safe range. The dynamic adjustment unit uses a feedback control algorithm to adjust the charging and discharging power according to the real-time monitoring data to ensure that the system operates within a set range. Let u(t) be the control input at time t, and there are:

[0016]

[0017] Among them, K p , K i , K d are proportional, integral, and differential control coefficients respectively, and e(t) is the deviation. Based on the dynamic model of the system, the future system state is predicted and the control input is optimized to ensure the performance of the system. At time t, there are:

[0018]

[0019] Among them, x k is the system state, x ref is the reference state, u k is the control input, Q and R are weight matrices, and the fault management unit detects and handles system faults. The faults include hardware faults, software faults, and system faults. The fault management unit handles the detected faults through fault detection, fault isolation, fault recovery, fault recording, and analysis.

[0020] Furthermore, the main functions of the energy storage converter include AC / DC conversion, DC / DC conversion, power regulation and power quality management. Through AC / DC conversion, alternating current (AC) is converted into direct current (DC), or direct current is converted into alternating current, so as to realize energy exchange between the energy storage system and the power grid. For low power, a single-phase rectifier is used to realize the conversion of AC to DC through a diode bridge. For high power, a six-pulse rectifier bridge is used to realize the conversion of AC to DC. There are:

[0021]

[0022] Among them, V AC is the AC voltage, V DC is the DC voltage. For DC / DC conversion, considering the charging and discharging processes of the energy storage system, we have:

[0023]

[0024] Where D is the duty cycle, V in is the input voltage, V out To output voltage, power regulation is used to control the charging and discharging power to achieve precise control of the energy storage system. Power quality management is used through filtering and reactive power compensation methods to improve power quality and stabilize grid frequency and voltage. Active filtering technology is used to detect harmonic components in the grid, generate corresponding compensation current, eliminate harmonic interference, and detect reactive power components in the grid to generate corresponding compensation power to stabilize grid voltage by adjusting the charging and discharging power of the energy storage system.

[0025] Furthermore, the supercapacitor subsystem provides instantaneous high-power output, smoothes grid fluctuations, and responds quickly to changes in grid frequency in a short period of time. Compared with traditional battery systems, the supercapacitor subsystem stores and releases energy through charge accumulation at the electrode-electrolyte interface. This process is achieved through two mechanisms: double-layer capacitance and pseudocapacitance. The double-layer capacitance mechanism mainly relies on physical adsorption of charge accumulation. Its non-Faraday process enables supercapacitors to store energy without involving chemical reactions, thereby greatly extending their service life. The pseudocapacitance mechanism is achieved through rapid Faraday reactions on the surface of electrode materials, which can release a large amount of energy in a short period of time and is suitable for responding to instantaneous high-power demands in the power grid. The supercapacitor subsystem can have a long cycle life and can maintain stable performance over millions of charge and discharge cycles. Supercapacitors exhibit low energy loss during high-frequency charge and discharge processes and have efficient energy management capabilities.

[0026] Furthermore, the supercapacitor subsystem utilizes charge accumulation at the electrode-electrolyte interface to store energy, including a double-layer capacitor mechanism and a pseudocapacitor mechanism, wherein the double-layer capacitor mechanism is based on the accumulation of charge at the electrode-electrolyte interface to form a double layer, and has: Where E is the stored energy, ∈ r is the dielectric constant, ∈0 is the vacuum dielectric constant, A is the electrode area, d m is the double layer thickness, and the pseudocapacitance mechanism is based on the fast Faraday reaction occurring on the surface of the electrode material: Where Q is the charge, I(x) is the current, t1 and t2 are time intervals, and the voltage range of each supercapacitor unit is generally 2.5V to 3V.

[0027] Furthermore, the lithium electronic system has a higher energy density than the supercapacitor subsystem, but a lower power density, and a relatively slow charge and discharge rate, which is suitable for long-term energy storage and release. The lithium electronic system includes a lithium electronic battery, which is composed of a positive electrode, a negative electrode, an electrolyte and a separator, wherein the porous film is used to isolate the positive and negative electrodes to prevent short circuits while allowing lithium ions to pass through. The lithium electronic battery is a rechargeable battery that uses the embedding and de-embedding of lithium ions between the positive and negative electrodes to store and release electrical energy. The lithium electronic system has a thermal management function, and heat conduction includes the influence of heat diffusion, convection and heat source terms. Heat conduction is expressed by a three-dimensional non-steady-state heat conduction equation as follows:

[0028]

[0029] Where T(x,y,z,t) is the temperature distribution at any point (x,y,z) inside the lithium-ion battery at time t, ρ is the density of the battery material, and c pis the specific heat capacity of the battery material, k x , k y , k z are the thermal conductivity of the battery material in the x, y, and z directions, respectively; J(x,y,z,t)E`(x,y,z,t) is the heat source caused by ohmic loss; η(x,y,z,t)ζ(x,y,z,t) is the heat source caused by electrochemical reaction;

[0030] is the heat source caused by the polarization effect, J(x,y,z,t) is the current density vector, E`(x,y,z,t) is the electric field strength, η(x,y,z,t) is the electrode overpotential, ζ(x,y,z,t) is the electrode reaction current density, C p (x, y, z) is the polarized capacitance. For lithium-ion batteries, it includes convection heat transfer boundary conditions and radiation heat transfer boundary conditions, which are expressed as follows:

[0031]

[0032] Where k' is the thermal conductivity, is the surface temperature gradient, h c is the convective heat transfer coefficient, T s is the battery surface temperature, T ∞ is the temperature of the cooling medium, ε is the emissivity of the battery surface, and σ is the Stefan-Boltzmann constant. By constructing a control objective function to control the parameters of the cooling system, the battery temperature is kept within a safe range.

[0033]

[0034] There are constraints:

[0035]

[0036]

[0037] Among them, T i (t) is the temperature of the ith lithium battery, T ref is the target reference temperature, w i is the weight coefficient of different lithium batteries, P cool is the power consumption of the cooling system, λ is the trade-off coefficient between power consumption and temperature deviation, T min , T max are the minimum and maximum temperatures allowed for the battery, is the maximum power limit of the cooling system.

[0038] Beneficial effects of the present invention: The present invention provides an efficient, stable and flexible solution for grid frequency regulation by introducing a new type of hybrid energy storage energy control system. The present invention combines two energy storage technologies, supercapacitor and lithium-ion battery, and gives full play to their respective advantages to form an energy storage architecture that can quickly respond to grid frequency fluctuations and balance energy for a long time. Supercapacitors, with their high power density and fast charging and discharging characteristics, can provide instantaneous high-power support when the grid frequency fluctuates, thereby effectively smoothing the short-term fluctuations of the grid. Lithium-ion batteries, with their high energy density advantages, undertake the long-term peak-shaving task of the grid and provide stable energy output. The present invention combines supercapacitors with lithium-ion batteries to achieve fast and stable frequency regulation on different time scales. In specific implementations, supercapacitors are used to quickly respond to frequency fluctuations in the grid and provide instantaneous power support, while lithium-ion batteries are responsible for long-term energy balance to ensure the stability of the grid under various operating conditions. Through this hybrid energy storage method, the system can effectively deal with the frequency fluctuation problem that is difficult to handle with traditional frequency modulation means, especially in grids with a high proportion of renewable energy access, providing a more flexible and reliable frequency modulation means. Through the optimization control of the thermal management system, the present invention can dynamically adjust the working status of supercapacitors and lithium-ion batteries based on real-time monitoring of the grid frequency, thereby achieving precise control of the grid frequency. The model predictive control method enables the system to optimally allocate energy storage resources while taking into account a variety of constraints, thereby maximizing the efficiency of the system while ensuring grid stability. In addition, the present invention also optimizes the thermal management of the energy storage system through a heat conduction model. In the process of modeling the heat source of lithium-ion batteries and supercapacitors, ohmic losses, electrochemical reactions, and polarization effects are comprehensively considered, so that the thermal management system can better control the temperature of the energy storage equipment, extend its service life, and improve the safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention is further illustrated by the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the invention. A person skilled in the art can obtain other drawings based on the following drawings without creative work.

[0040] Figure 1 It is a system schematic diagram of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on 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.

[0042] See also Figure 1 The present invention will be further described in conjunction with the following examples.

[0043] See also Figure 1 The present invention aims to provide a hybrid energy storage control system for power grid frequency regulation.

[0044] It is characterized by comprising the following steps:

[0045] A hybrid energy storage control system for power grid frequency modulation includes a coordination controller, a power storage converter (PCS), a supercapacitor subsystem, and a lithium electronic system; the coordination controller includes a coordination controller data terminal and a coordination controller control terminal, the coordination controller data terminal is responsible for collecting, processing and analyzing real-time data and providing decision support, the coordination controller control terminal is responsible for executing the charging and discharging strategy generated by the optimization algorithm and controlling the operation of each energy storage unit, the energy storage converter is responsible for the conversion and transmission of electric energy and realizes the energy exchange between the energy storage system and the power grid, the supercapacitor subsystem provides instantaneous high-power output, smoothes power grid fluctuations and assists in power grid frequency modulation, and the lithium electronic system is used for power grid peak regulation, backup power supply and smooth output of renewable energy.

[0046] Specifically, the coordination controller comprehensively monitors, analyzes and controls the entire system to ensure that the energy storage system can accurately dispatch energy according to the demand and status of the power grid. The coordination controller includes a coordination controller data end and a coordination controller control end. The coordination controller data end cleans, filters and converts the collected data to eliminate noise and abnormal values ​​to ensure the accuracy and reliability of the data. It can estimate the status of the energy storage system in real time. The estimation result provides a basis for the system's predictive analysis, so that the coordination controller can predict the needs of the power grid and formulate corresponding charging and discharging strategies. The coordination controller control end can dynamically adjust the charging and discharging power of the energy storage system according to the analysis results provided by the coordination controller data end to ensure that the system can operate in the best state under different working conditions. The coordination controller control end has real-time monitoring and dynamic adjustment capabilities. Through the feedback control mechanism, the coordination controller can quickly adjust the operating status of the energy storage system when the power grid frequency fluctuates, provide rapid response, and maintain the stability of the power grid.

[0047] Specifically, the coordination controller data end includes a data acquisition unit, a data processing unit, a state estimation unit, a prediction analysis unit, and a decision support unit. The data acquisition unit collects voltage, current, frequency, temperature, and remaining power data of the power grid and the energy storage system in real time. The data processing unit performs data cleaning, filtering, and format conversion on the collected data, removes noise and outliers through data cleaning, smoothes the data using a low-pass filter method, eliminates high-frequency noise, and de-dimensionalizes the data so that the statistical differences between dimensions are eliminated and the format conversion is completed; the state estimation unit estimates the current state of the energy storage system based on real-time data and mathematical models, and establishes a state estimation model:

[0048]

[0049]

[0050]

[0051] in, Predict the state of the data at step k, Update the state for the data in step k-1, μ k-1 is the control quantity of the system in the k-1th step, A, B, C are the system matrices, Update the state of the data in step k, P k-1|k-1 is the updated prediction error covariance of the k-1th step, P k|k is the updated prediction error covariance at step k, z k is the data observation value, σ and is the Gaussian variance, GAUSS(0,σ) represents a Gaussian function with a mean of 0 and a variance of σ, cov is the covariance function, I is the unit matrix, and the prediction analysis unit records the data update state matrix as X, holds, where α and β are constants, p is the autoregressive order, q is the moving average order, φ is the autoregressive coefficient, and θ j is the moving average coefficient, ε(k) is the error term of the kth step, and the decision support unit combines the state estimation and prediction analysis results to generate the charging and discharging strategy of the energy storage system.

[0052] Specifically, the control end of the coordination controller includes a strategy execution unit, a real-time monitoring unit, a dynamic adjustment unit, and a fault management unit. The strategy execution unit receives and executes the charging and discharging strategy generated by the optimization algorithm to control the operating status of the energy storage device. The real-time monitoring unit monitors the real-time operating status of the power grid and the energy storage system to ensure that the system operates within a safe range. The dynamic adjustment unit uses a feedback control algorithm to adjust the charging and discharging power according to the real-time monitoring data to ensure that the system operates within a set range. Let u(t) be the control input at time t, and there are:

[0053]

[0054] Among them, K p , K i , K d are proportional, integral, and differential control coefficients respectively, and e(t) is the deviation. Based on the dynamic model of the system, the future system state is predicted and the control input is optimized to ensure the performance of the system. At time t, there are:

[0055]

[0056] Among them, x k is the system state, x ref is the reference state, u k is the control input, Q and R are weight matrices, and the fault management unit detects and handles system faults. The faults include hardware faults, software faults, and system faults. The fault management unit handles the detected faults through fault detection, fault isolation, fault recovery, fault recording, and analysis.

[0057] Specifically, the main functions of the energy storage converter include AC / DC conversion, DC / DC conversion, power regulation and power quality management. Through AC / DC conversion, alternating current (AC) is converted into direct current (DC), or direct current is converted into alternating current, so as to realize energy exchange between the energy storage system and the power grid. For low power, a single-phase rectifier is used to realize the conversion of AC to DC through a diode bridge. For high power, a six-pulse rectifier bridge is used to realize the conversion of AC to DC. There are:

[0058]

[0059] Among them, V AC is the AC voltage, V DC is the DC voltage. For DC / DC conversion, considering the charging and discharging processes of the energy storage system, we have:

[0060]

[0061] Where D is the duty cycle, V in is the input voltage, V out To output voltage, power regulation is used to control the charging and discharging power to achieve precise control of the energy storage system. Power quality management is used through filtering and reactive power compensation methods to improve power quality and stabilize grid frequency and voltage. Active filtering technology is used to detect harmonic components in the grid, generate corresponding compensation current, eliminate harmonic interference, and detect reactive power components in the grid to generate corresponding compensation power to stabilize grid voltage by adjusting the charging and discharging power of the energy storage system.

[0062] Specifically, the supercapacitor subsystem provides instantaneous high-power output, smoothes grid fluctuations, and responds quickly to changes in grid frequency in a short period of time. Compared with traditional battery systems, the supercapacitor subsystem stores and releases energy through charge accumulation at the electrode-electrolyte interface. This process is achieved through two mechanisms: double-layer capacitance and pseudocapacitance. The double-layer capacitance mechanism mainly relies on physical adsorption of charge accumulation. Its non-Faraday process enables supercapacitors to store energy without involving chemical reactions, thereby greatly extending their service life. The pseudocapacitance mechanism is achieved through rapid Faraday reactions on the surface of electrode materials, which can release a large amount of energy in a short period of time and is suitable for responding to instantaneous high-power demands in the power grid. The supercapacitor subsystem can have a long cycle life and can maintain stable performance over millions of charge and discharge cycles. Supercapacitors exhibit low energy loss during high-frequency charge and discharge processes and have efficient energy management capabilities.

[0063] Specifically, the supercapacitor subsystem utilizes charge accumulation at the electrode-electrolyte interface to store energy, including a double-layer capacitor mechanism and a pseudocapacitor mechanism, wherein the double-layer capacitor mechanism is based on the accumulation of charge at the electrode-electrolyte interface to form a double layer, including: Where E is the stored energy, ∈ r is the dielectric constant, ∈0 is the vacuum dielectric constant, A is the electrode area, d m is the double layer thickness, and the pseudocapacitance mechanism is based on the fast Faraday reaction occurring on the surface of the electrode material: Where Q is the charge, I(t) is the current, t1 and t2 are time intervals, and the voltage range of each supercapacitor unit is generally 2.5V to 3V.

[0064] Specifically, the lithium electronic system has a higher energy density than the supercapacitor subsystem, but a lower power density, and a relatively slow charge and discharge rate, and is suitable for long-term energy storage and release. The lithium electronic system includes a lithium electronic battery, which is composed of a positive electrode, a negative electrode, an electrolyte and a separator, wherein the porous film is used to isolate the positive and negative electrodes to prevent short circuits while allowing lithium ions to pass through. The lithium electronic battery is a rechargeable battery that uses the embedding and de-embedding of lithium ions between the positive and negative electrodes to store and release electrical energy. The lithium electronic system has a thermal management function, and heat conduction includes the influence of heat diffusion, convection and heat source terms. Heat conduction is expressed by a three-dimensional non-steady-state heat conduction equation as follows:

[0065]

[0066] Where T(x,y,z,t) is the temperature distribution at any point (x,y,z) inside the lithium-ion battery at time t, ρ is the density of the battery material, and c pis the specific heat capacity of the battery material, k x , k y , k z are the thermal conductivity of the battery material in the x, y, and z directions, respectively; J(x,y,z,t)E`(x,y,z,t) is the heat source caused by ohmic loss; η(x,y,z,t)ζ(x,y,z,t) is the heat source caused by electrochemical reaction;

[0067] is the heat source caused by the polarization effect, J(x,y,z,t) is the current density vector, E`(x,y,z,t) is the electric field strength, η(x,y,z,y) is the electrode overpotential, ζ(x,y,z,t) is the electrode reaction current density, C p (x, y, z) is the polarized capacitance. For lithium-ion batteries, it includes convection heat transfer boundary conditions and radiation heat transfer boundary conditions, which are expressed as follows:

[0068]

[0069] Where k' is the thermal conductivity, is the surface temperature gradient, h c is the convective heat transfer coefficient, T s is the battery surface temperature, T ∞ is the temperature of the cooling medium, ε is the emissivity of the battery surface, and σ is the Stefan-Boltzmann constant. By constructing a control objective function to control the parameters of the cooling system, the battery temperature is kept within a safe range.

[0070]

[0071] There are constraints:

[0072]

[0073]

[0074] Among them, T i (t) is the temperature of the ith lithium battery, T ref is the target reference temperature, w i is the weight coefficient of different lithium batteries, P cool is the power consumption of the cooling system, λ is the trade-off coefficient between power consumption and temperature deviation, T min , T max are the minimum and maximum temperatures allowed for the battery, is the maximum power limit of the cooling system.

[0075] Beneficial effects of the present invention: The present invention provides an efficient, stable and flexible solution for grid frequency regulation by introducing a new type of hybrid energy storage energy control system. The present invention combines two energy storage technologies, supercapacitor and lithium-ion battery, to form an energy storage architecture that can quickly respond to grid frequency fluctuations and balance energy for a long time. Supercapacitors, with their high power density and fast charging and discharging characteristics, can provide instantaneous high-power support when the grid frequency fluctuates, thereby effectively smoothing the short-term fluctuations of the grid. Lithium-ion batteries, with their high energy density advantages, undertake the long-term peak-shaving task of the grid and provide stable energy output. The present invention combines supercapacitors with lithium-ion batteries to achieve fast and stable frequency regulation on different time scales. In specific implementations, supercapacitors are used to quickly respond to frequency fluctuations in the grid and provide instantaneous power support, while lithium-ion batteries are responsible for long-term energy balance to ensure the stability of the grid under various operating conditions. Through this hybrid energy storage method, the system can effectively deal with frequency fluctuations that are difficult to handle with traditional frequency modulation methods, especially in grids with a high proportion of renewable energy access, providing a more flexible and reliable frequency modulation method. Through the optimization control of the thermal management system, the present invention can dynamically adjust the working status of supercapacitors and lithium-ion batteries based on real-time monitoring of the grid frequency, thereby achieving precise control of the grid frequency. The model predictive control method enables the system to optimally allocate energy storage resources while taking into account a variety of constraints, thereby maximizing the efficiency of the system while ensuring grid stability. In addition, the present invention also optimizes the thermal management of the energy storage system through a heat conduction model. In the process of modeling the heat source of lithium-ion batteries and supercapacitors, ohmic losses, electrochemical reactions, and polarization effects are comprehensively considered, so that the thermal management system can better control the temperature of the energy storage equipment, extend its service life, and improve the safety of the system.

[0076] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A hybrid energy storage control system for power grid frequency modulation, characterized in that: It includes a coordination controller, a power storage converter (PCS), a supercapacitor subsystem, and a lithium electronic system; the coordination controller includes a coordination controller data terminal and a coordination controller control terminal. The coordination controller data terminal is responsible for collecting, processing and analyzing real-time data and providing decision support. The coordination controller control terminal is responsible for executing the charging and discharging strategy generated by the optimization algorithm and controlling the operation of each energy storage unit. The energy storage converter is responsible for the conversion and transmission of electric energy and realizes the energy exchange between the energy storage system and the power grid. The supercapacitor subsystem provides instantaneous high-power output, smoothes power grid fluctuations and assists in power grid frequency modulation. The lithium electronic system is used for power grid peak regulation, backup power supply, and smooth output of renewable energy. The coordination controller comprehensively monitors, analyzes and controls the entire system to ensure that the energy storage system can accurately dispatch energy according to the demand and status of the power grid. The coordination controller includes a coordination controller data end and a coordination controller control end. The coordination controller data end cleans, filters and converts the collected data to eliminate noise and abnormal values ​​to ensure the accuracy and reliability of the data. It can estimate the state of the energy storage system in real time. The estimation result provides a basis for the system's predictive analysis, so that the coordination controller can predict the demand of the power grid and formulate corresponding charging and discharging strategies. The coordination controller control end can dynamically adjust the charging and discharging power of the energy storage system according to the analysis results provided by the coordination controller data end to ensure that the system can operate in the best state under different working conditions. The coordination controller control end has real-time monitoring and dynamic adjustment capabilities. Through the feedback control mechanism, the coordination controller can adjust the operating state of the energy storage system when the power grid frequency fluctuates, provide rapid response, and maintain the stability of the power grid. The data end of the coordination controller includes a data acquisition unit, a data processing unit, a state estimation unit, a prediction analysis unit, and a decision support unit. The data acquisition unit collects voltage, current, frequency, temperature, and remaining power data of the power grid and the energy storage system in real time. The data processing unit performs data cleaning, filtering, and format conversion on the collected data, removes noise and outliers through data cleaning, smoothes the data using a low-pass filter method, eliminates high-frequency noise, and de-dimensionalizes the data so that the statistical differences caused by the dimensions are eliminated and the format conversion is completed; the state estimation unit estimates the current state of the energy storage system based on real-time data and mathematical models, and establishes a state estimation model: in, Predict the state of the data at step k, Update the state for the data in step k-1, μ k-1 is the control quantity of the system in the k-1th step, A, B, C are system matrices, Update the state of the data in step k, P k-1|k-1 is the updated prediction error covariance of the k-1th step, P k|k is the updated prediction error covariance at step k, z k is the data observation value, σ and is the Gaussian variance, GAUSS(0,σ) represents a Gaussian function with a mean of 0 and a variance of σ, cov is the covariance function, I is the unit matrix, and the prediction analysis unit records the data update state matrix as X, holds, where α and β are constants, p is the autoregressive order, q is the moving average order, and φ i is the autoregressive coefficient, θ j is the moving average coefficient, ε(k) is the error term of the kth step, and the decision support unit combines the state estimation and prediction analysis results to generate the charging and discharging strategy of the energy storage system; The control end of the coordination controller includes a strategy execution unit, a real-time monitoring unit, a dynamic adjustment unit, and a fault management unit. The strategy execution unit receives and executes the charging and discharging strategy generated by the optimization algorithm to control the operating status of the energy storage device. The real-time monitoring unit monitors the real-time operating status of the power grid and the energy storage system to ensure that the system operates within a safe range. The dynamic adjustment unit uses a feedback control algorithm to adjust the charging and discharging power according to the real-time monitoring data to ensure that the system operates within a set range. Let u(t) be the control input at time t, and there are: Among them, K p , K i , K d are proportional, integral, and differential control coefficients respectively, and e(t) is the deviation. Based on the dynamic model of the system, the future system state is predicted and the control input is optimized to ensure the performance of the system. At time t, there are: Among them, x k is the system state, x ref is the reference state, u k is the control input, Q and R are weight matrices, and the fault management unit detects and handles system faults. The faults include hardware faults, software faults, and system faults. The fault management unit handles the detected faults through fault detection, fault isolation, fault recovery, fault recording, and analysis.

2. A hybrid energy storage control system for power grid frequency modulation according to claim 1, characterized in that: The main functions of the energy storage converter include AC / DC conversion, DC / DC conversion, power regulation and power quality management. Through AC / DC conversion, alternating current (AC) is converted into direct current (DC), or direct current is converted into alternating current, so as to realize energy exchange between the energy storage system and the power grid. For low power, a single-phase rectifier is used to realize the conversion from AC to DC through a diode bridge. For high power, a six-pulse rectifier bridge is used to realize the conversion from AC to DC. There are: Among them, V AC is the AC voltage, V DC is the DC voltage. For DC / DC conversion, considering the charging and discharging processes of the energy storage system, we have: Where D is the duty cycle, V in is the input voltage, V out To output voltage, power regulation is used to control the charging and discharging power to achieve precise control of the energy storage system. Power quality management is used through filtering and reactive power compensation methods to improve power quality and stabilize grid frequency and voltage. Active filtering technology is used to detect harmonic components in the grid, generate corresponding compensation current, eliminate harmonic interference, and detect reactive power components in the grid to generate corresponding compensation power to stabilize grid voltage by adjusting the charging and discharging power of the energy storage system.

3. A hybrid energy storage control system for power grid frequency modulation according to claim 1, characterized in that: The supercapacitor subsystem provides instantaneous high-power output, smoothes grid fluctuations, and responds to changes in grid frequency in a short time. The supercapacitor subsystem stores and releases energy through charge accumulation at the electrode-electrolyte interface. This process is achieved through two mechanisms: double-layer capacitance and pseudocapacitance. The double-layer capacitance mechanism mainly relies on physical adsorption of charge accumulation. Its non-Faraday process enables supercapacitors to store energy without involving chemical reactions, thereby extending their service life. The pseudocapacitance mechanism is achieved through rapid Faraday reactions on the surface of electrode materials, which can release a large amount of energy in a short time and is suitable for responding to instantaneous high-power demands in the grid. The supercapacitor subsystem can have a long cycle life and can maintain stable performance over millions of charge and discharge cycles.

4. A hybrid energy storage control system for power grid frequency modulation according to claim 3, characterized in that: The supercapacitor subsystem utilizes the charge accumulation at the electrode-electrolyte interface to store energy, including a double-layer capacitor mechanism and a pseudocapacitor mechanism, wherein the double-layer capacitor mechanism is based on the accumulation of charge at the electrode-electrolyte interface to form a double layer, and has: Where E is the stored energy, ∈ r is the dielectric constant, ∈0 is the vacuum dielectric constant, D is the electrode area, d m is the double layer thickness, and the pseudocapacitance mechanism is based on the fast Faraday reaction occurring on the surface of the electrode material: Where Q is the charge, I(t) is the current, t1 and t2 are time intervals, and the voltage range of each supercapacitor unit is 2.5V to 3V.

5. A hybrid energy storage control system for power grid frequency modulation according to claim 1, characterized in that: Compared with the supercapacitor subsystem, the lithium electronic system has a higher energy density, but a lower power density, and a relatively slow charge and discharge rate, which is suitable for long-term energy storage and release. The lithium electronic system includes a lithium electronic battery, which is composed of a positive electrode, a negative electrode, an electrolyte and a separator, wherein the porous film is used to isolate the positive and negative electrodes to prevent short circuits and allow lithium ions to pass through. The lithium electronic battery is a rechargeable battery that uses the embedding and de-embedding of lithium ions between the positive and negative electrodes to store and release electrical energy. The lithium electronic system has a thermal management function, and heat conduction includes the influence of heat diffusion, convection and heat source terms. Heat conduction is expressed by a three-dimensional non-steady-state heat conduction equation as follows: Where T(x,y,z,t) is the temperature distribution at any point (x,y,z) inside the lithium-ion battery at time t, ρ is the density of the battery material, and c p is the specific heat capacity of the battery material, k x , k y , k z are the thermal conductivity of the battery material in the x, y, and z directions, respectively. J(x,y,z,t)E`(x,y,z,t) is the heat source caused by Ohmic loss. η(x,y,z,t)ζ(x,y,z,t) is the heat source caused by the electrochemical reaction. is the heat source caused by the polarization effect, J(x,y,z,t) is the current density vector, E`(x,y,z,t) is the electric field strength, η(x,y,z,t) is the electrode overpotential, ζ(x,y,z,t) is the electrode reaction current density, C p (x, y, z) is the polarized capacitance. For lithium-ion batteries, it includes convection heat transfer boundary conditions and radiation heat transfer boundary conditions, which are expressed as follows: Where k' is the thermal conductivity, is the surface temperature gradient, h c is the convective heat transfer coefficient, T s is the battery surface temperature, T ∞ is the temperature of the cooling medium, ε is the emissivity of the battery surface, and σ is the Stefan-Boltzmann constant. By constructing a control objective function to control the parameters of the cooling system, the battery temperature is kept within a safe range. There are constraints: Among them, T i (t) is the temperature of the ith lithium battery, T ref is the target reference temperature, w i is the weight coefficient of different lithium batteries, P cool (t) is the power consumption of the cooling system, λ is the trade-off coefficient between power consumption and temperature deviation, T min , T max are the minimum and maximum temperatures allowed for the battery, is the maximum power limit of the cooling system.

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