Application of energy storage systems for frequency regulation service

Frequency control aims to maintain the nominal frequency of the power system through compensating the generation-load mismatch. In addition to fast response generators, energy storage systems can be exploited to provide frequency regulation service due to their fast ramping characteristic. In this paper, we propose a solution to leverage energy storage systems deployed in the distribution networks for secondary frequency regulation service by considering the uncertainty in system disturbances, the energy storage availability, and the AC power flow model. In particular, we tackle the uncertainty in the frequency deviations and alleviate the problem associated with the limited energy storage capacity by using a risk minimization technique. We formulate a linear program to determine the frequency regulation signals to schedule the energy storage systems by adopting the concept of conditional value-at-risk (CVaR). It enables us to minimize the risk of deviation from the nominal frequency after performing frequency regulation, while satisfying the operation constraints of the distribution network. Simulations are performed on an IEEE 37-bus test feeder with three energy storage systems that participate in the frequency regulation service. Results show that by using the proposed approach, the charging/discharging of the energy storage systems can be scheduled to regulate the frequency, and the risk of energy storage systems not being able to contribute to future regulation service can be reduced.