Optimal sizing of Hybrid Energy Storage Systems to mitigate wind power fluctuations

Wind energy penetration level may be adversely impacted by frequency deviations as a result of wind power fluctuations. Energy Storage System (ESS) can be a viable candidate for mitigating wind power fluctuations. However, economic considerations for ESS may cause significant limits in implementation. Therefore, effectiveness and optimal size of ESS are important to study. This paper proposes a method to find an optimal size of sodium sulfur battery energy storage and pumped storage hydro to accommodate high penetrations of wind energy. The proposed method decomposes the imbalance power by using Discrete Fourier Transform (DFT) to fast and slow components. Hence, different ESS technologies can be dispatched based on their effectiveness in various time spans. For instance, the slower pumped storage hydro can compensate slow cycles, and the fast-acting batteries can be dispatched to balance smaller and more frequent cycles. This method can be used in the planning of different ESS technologies. Comparative studies on real wind data from Bonneville Power Administration (BPA) shows the efficacy of the proposed method.