Study On Operation Characteristics And Control Strategy Of Energy Storage System In Wind-storage Combined System

With the continuous innovation and development of science and technology in China,wind power generation,as an important power generation technology,has been correspondingly expanded both in depth and breadth,and more countries and regions in the world attach great importance to it.As a special renewable energy technology,there is a certain degree of uncertainty in wind power generation,there will be more intermittent,and the volatility is also large.The stability of voltage and the frequency of power grid will be affected by the instability of wind power generation to some extent,and with the increase of wind power permeability in China,this decisive effect is becoming more and more prominent.Benefit from the emergence and operation of modern energy storage systems,the instability of wind power generation in actual operation can be improved.With the help of the joint operation of energy storage systems and wind farms,the purpose of reducing the volatility of wind power generation can be well achieved.This paper firstly analyzes the development status of wind power at home and abroad,the technical issues of large-scale wind power grid connection,and the research status of energy storage technologies.The mathematical models of doubly-fed wind power generators,batteries,and super capacitors are established respectively,and its basic working principle is analyzed.The simulation model of battery and super capacitor is established on the platform of MATLAB/SIMULINK to analyze the charge and discharge characteristics.The characteristics of the topological structure of the centralized energy storage and the distributed energy storage are briefly analyzed,and it is concluded that the centralized energy storage has a better power smoothing capability.Because the wavelet packet decomposition theory can decompose the output power of wind farms in multi-scale,the low-frequency components after wavelet packet decompositionSecondly,the Fourier transform is used to analysis the frequency spectrum characteristics of wind power.On the basis of analyzing the time-domain and frequency-domain characteristics of wind power output power fluctuation,the effects of two control algorithms,the first-order low-pass filtering and the wavelet packet decomposition filtering,are compared.Because the wavelet packet decomposition theory can decompose the output power of wind farms in multi-scale,the low-frequency components after wavelet packet decomposition is regarded as the expected value of wind power grid connection,and the most high-frequency and sub-high-frequency components are compensated by hybrid energy storage system.Combined with the energy distribution characteristics of super capacitor and battery energy storage system,a hybrid energy storage system model for wind power smoothing is constructed.Finally,according to the wavelet packet decomposition,the wind power grid-connected power and the primary power command of the hybrid energy storage system are obtained.Within the hybrid energy storage system,according to the state of charge(SOC)of the super capacitor,the power instructions of batteries and super capacitors are modified by using fuzzy optimal control strategy,and the optimized hybrid energy storage power distribution command is obtained.The example analysis shows that the proposed strategy can achieve a reasonable distribution of wind power,ensure that the state of charge of hybrid energy storage works in a reasonable range,effectively improved the effect of fluctuation in output power of wind power,and ensure long-term stable operation of hybrid energy storage system.