| Due to the gradual depletion of coal resources and the restrictions of UN on carbon emissions,the development of renewable energy has become the main direction of future power development.Combine energy and power plans of various countries,renewable energy will gradually shift from complementary to alternative energy sources.The large-scale development of renewable energy has put forward higher requirements for the power grid.It is an urgent problem to improve the absorption capacity of renewable energy.In recent years,the installed capacity of wind power continues to rise,but the low wind power consumption rate makes the phenomenon of abandoning wind power common.How to improve wind power access rate and reduce wind power output has become the research direction of scholars at home and abroad in recent years.As a stable and flexible power source,energy storage provides a new idea for the development of wind power.In order to improve the power generation characteristics of the output power of the wind farm,the energy storage system needs to meet the control requirements in the two dimensions of power and energy.For short time scale and high frequency energy storage requirements,the power storage is implemented.The energy storage requirements of long time scale and low frequency are implemented by energy storage.In this paper,according to the characteristics of different energy storage methods,flywheel energy storage and lithium battery energy storage are complementary to each other to design a hybrid energy storage system structure for wind power suppression.The capacity configuration and control strategy of hybrid energy storage are studied.The main contents are as follows:(1)Firstly,this paper introduces the principles and characteristics of the two energy storage methods,designs the overall structure topology of the hybrid energy storage system by adopting the centralized energy storage method,and carries out mathematical modeling of the system structure of the two energy storage methods according to the working principles of the two energy storage methods.(2)In terms of power frequency division,the wind power output curve is smoothed by sliding filtering method,and the smoothed curve after filtering out high frequency power and disturbance power is the most smooth target.Then the power to be compensated by storage is decomposed into a series of modal power curves which vary according to the frequency by empirical mode decomposition.According to the principle of the lowest energy of the two modes,the frequency division power was determined,and the compensation power was decomposed into high frequency power and low frequency power.A control strategy formulation method considering the real-time SOC of stored energy is proposed.According to the characteristics of the energy storage system,in accordance with the principle of reducing The Times of charging and discharging of lithium battery energy storage and minimizing the capacity of flywheel energy storage,considering the real-time state of charge of the energy storage system,the control strategy is formulated to make the two energy storage systems correspond to the high frequency and low frequency power respectively.The compensation coefficient is set according to the state of charge of the energy storage system to avoid the overcharge and over-discharge of the energy storage system.(3)The wind power stability was defined by energy storage,the relationship between different energy storage parameters and wind power stability was fitted by BP neural network,and the energy storage parameters that did not meet the requirements of the stability were directly eliminated in the solution.Energy storage capacity and power are configured with low-cost objective functions.Particle Swarm Optimization Algorithm and Simulated Annealing Method are proposed to solve the above optimization model.At last,the economy of the energy storage system configuration is analyzed,and suggestions for the future development of energy storage are put forward. |
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