Capacity optimization of hybrid energy storage for smoothing power fluctuations based on spectrum analysis

Reasonable configuration of hybrid energy storage system helps to reduce the influence of power fluctuations of wind output power effectively as well as the system cost. Not only considering the charge-discharge loss of energy storage, converter loss, the limit of State of Charge(SOC), but also practical parameters of energy storage device on the market, this paper proposes the method of optimal capacity configuration of hybrid energy storage system(HESS), which is composed of sodium-sulfur battery and super-capacitor based on discrete Fourier transform(DFT). Furthermore, in order to verify the validity of capacity optimization of HESS using proposed method, the model of a wind farm with HESS is established to simulate. The results show that HESS using the proposed method for optimal capacity allocation can level the fluctuations of wind out power effectively without the phenomenon of over-charging or over-discharging in energy storage devices.