Abstract—The principal characteristics of wind power are randomness and intermittence. In order to restrain the adverse effect of these characteristics of wind power on the operation of power grids, this paper proposes a wind power smoothing method based on time-frequency analysis of wind power fluctuations. Firstly, the time when fluctuations exceed the variation limit is detected and used as the time-domain characteristics. Then wind power fluctuations are decomposed into several different frequency bands through wavelet packet transform, and the energy ratio of each frequency band, which is taken as the frequency-domain characteristics of wind power fluctuations, is calculated out according to the wavelet packet spectrum. Finally, the time-frequency distribution characteristics of wind power fluctuations are obtained by combining the time-domain characteristics and the frequency-domain characteristics and are used to smooth wind power. The proposed method is verified through wind farms in China and the simulation results show that the cumulative power and the charging-discharging switching times of energy storage devices can be reduced through this method compared with the traditional wavelet-based method. Therefore, the method presented in this paper helps to reduce the cost of energy storage configuration in wind farms, hence improving the economic benefits of wind farms.
Keywords—Wind power, Fluctuation smoothing, Time-frequency analysis, Time-domain, Frequency-domain, Wavelet packet, Energy storage;

 

Wind power;Fluctuation smoothing,;Time-frequency analysis,;Time-domain;Frequency-domain;Wavelet packet;Energy storage