Optimal planning and operation of energy storage systems in radial networks for wind power integration with reserve support

Though energy storage system (ESS) is a promising approach to alleviate the variability of non-dispatchable wind power and other forms of renewable energy sources, its high investment cost has impeded its wide deployment. Aiming at exploiting the arbitrage benefit of ESS in reserve market and raising revenue of shareholders, this study explores the optimal planning and operation of ESS in radial networks. Besides load balancing, ESS is used to provide three kinds of operating reserve services in presence of high wind power penetration, including spinning reserve, upward and downward regulation reserves. In light of the capacity limitation of ESS, the time duration of reserve provision has been taken into account. In the proposed model, unit commitment and AC optimal power flow (AC-OPF) are combined together over sequential time series to find the optimal location and size of ESSs. In order to reduce the computational complexity, the extended DistFlow model of AC-OPF is adopted to convert the problem into a mixed-integer second-order cone programming. Numerical studies on the IEEE 34-bus distribution test feeder are used to investigate the effects of ESS with respect to various penetration levels of wind power and load scales.