A new control method of multiple sets of battery energy storage system for load frequency control in power system with massive integration of renewable energy resources

Massive integration of generations from renewable energy sources such as photovoltaic (PV) and wind power generations into power systems causes large frequency fluctuations because their outputs are intermittent in nature. Battery energy storage system (BESS) is considered as one of solutions to this problem. In operation of the BESSs, their characteristics should be taken into consideration. For example, to extend the life time of the BESS, its state of charge (SOC) should not reach the upper or lower limit. In addition, efficiency of the BESS inverter is degraded when its output is low. In this paper, when multiple sets of BESSs and different kinds of BESSs are installed into a power grid, a new control method of the BESSs for load frequency control taking into account their characteristics is proposed. Numerical simulations for the multi-machine power system model are carried out to show effectiveness of the proposed control method. It is made clear that their total inverter loss can be reduced and all of their SOC can be always kept within the limits while contributing to the frequency control by the proposed method.