Since the penetration level of Photovoltaic (PV) system continuously increases, the negative impact caused by the fluctuation of PV power output needs to to be carefully managed. This paper proposes a coordinated control algorithm based on a discrete wavelet transform to eliminate both short-term and long-term fluctuations by using hybrid energy storage system (HESS). While the short-term fluctuation is mitigated by using an electric double-layer capacitor (EDLC), the longterm one is reduced by the support of a Li-ion battery. The effectiveness of the proposed algorithm has been tested by using Matlab/Simulink program. The simulation results demonstrate that the HESS with the proposed control algorithm can indeed assist in dealing with the variation of PV power output. | Trần Thái Trung và Đtg Tạp chí KHOA HỌC & CÔNG NGHỆ 139(09): 223 - 228 THE WAVELET-BASED CONTROL ALGORITHM OF HYBRID ENERGY STORAGE SYSTEM FOR REDUCING FLUCTUATION OF PHOTOVOLTAIC SYSTEM Tran Thai Trung*, Nguyen Minh Y College of Technology - TNU SUMMARY Since the penetration level of Photovoltaic (PV) system continuously increases, the negative impact caused by the fluctuation of PV power output needs to to be carefully managed. This paper proposes a coordinated control algorithm based on a discrete wavelet transform to eliminate both short-term and long-term fluctuations by using hybrid energy storage system (HESS). While the short-term fluctuation is mitigated by using an electric double-layer capacitor (EDLC), the longterm one is reduced by the support of a Li-ion battery. The effectiveness of the proposed algorithm has been tested by using Matlab/Simulink program. The simulation results demonstrate that the HESS with the proposed control algorithm can indeed assist in dealing with the variation of PV power output. Keywords: Photovoltaic System, Hybrid Energy Storage System (EESS), Discrete Wavelet Transform, Fluctuation Mitigation, Li-ion Battery, Electric Double-Layer Capacitor (EDLC) INTRODUCTION* Recently, the exhaustion of fossil fuels and the critical environment pollution have led to the need to develop new clean energy sources. Photovoltaic energy, a type of renewable and environmental-friendly, is considered as a prospective replacement for conventional energy sources. The presence of PV systems opens opportunities and poses new challenges. PV systems can effectively reduce power losses and on-peak operation costs, improve voltage profile, defer system upgrades, and improve system intergrity, reliability and efficiency with sophisticated control scheme [1]. However, because of the stochastic and intermittent characteristic of sunlight, the resulting fluctuation in power output is the greatest obstacle to the increasing penetration level of PV .
