PV power plant using hybrid energy storage system with improved efficiency

In the last few years, the stationary battery started to be used as energy storage systems (ESS) in order to enhance the supply reliability of large-scale PV power plants, thereby enabling high penetration of PV-generated electricity into the electrical grid. Lately, one of the flow battery energy storage technologies, namely the Vanadium Redox Battery (VRB) started to be commercialised in the range of Mega-watts and it has attracted increasing interest of the renewable energy industry. The integration of a VRB-ESS with a large-scale PV plant also brings some new technical challenges. For instance, the VRB efficiency drops significantly when its output power is lower than 0.2 pu of its rated power. This paper proposes a VRB and supercapacitor (SC) hybrid energy storage system (HESS) to improve the efficiency of a standard sole VRB-ESS. The HESS management strategy is also introduced in this paper. An equivalent electrical model of the PV system including the HESS was implemented in MATLAB/Simulink/PLECS environment to analyse the operational performance of the proposed system.