Sizing and Operation of a Hybrid Energy Storage System to Compensate Forecast Errors of Wind Farms - An Approach

This paper proposes a frequency domain based sizing method for a grid scale hybrid energy storage system (HESS) to compensate forecast errors from wind farms. The HESS combines lithium-ion batteries (LIB) and supercapacitors (SC) and uses their inherent properties for compensating different parts of the frequency spectrum from the forecast error. Therefore, the forecast error is transformed from the time to the frequency domain by the fast Fourier transformation (FFT). Then cut-off frequencies for the LIB and the SC are determined to calculate a techno-economical sizing ratio between LIB and SC by considering the service life of the LIB. A cycle based degradation model combined with a rainflow algorithm is used to calculate the service life of the LIB to identify the optimal sizing and provide the lowest possible annual costs. Furthermore, the sizing calculations are confirmed by simulating the operation of the HESS.