Efficiency improvement of pumped storage system for MW scale off-grid PV plants

The photovoltaic market has been growing at a fast rate in the last two decades, and in 2014 reached a global capacity of about 180GW. Due to the increasing penetration level, large-scale energy storage systems that can compensate for its fluctuations become increasingly important. In case of off-grid systems, suitable energy storage is naturally a necessity. In areas with favorable geographical properties, pumped storage has an excellent potential to be applied with large-scale PV plants. The performance of a pumped storage system at MW power level, connected with an off-grid PV plant, is analyzed in this paper, considering the variable character of the PV power. An efficiency increase of the pumped storage system is obtained by means of an improved control of the motor for pump's drive. The system is tested and validated on a RTDS (Real Time Digital Simulator) platform.