Energy Storage for Short-Term Frequency Stability Enhancement in Low-Inertia Power Systems

Power systems with large scale integration of inverter interfaced generation plants become vulnerable to short term frequency instability. The short term frequency stability is related to limiting the RoCoF and frequency nadir within acceptable standards following a contingency. Failure to limit frequency nadir and RoCoF can result in the activation of RoCoF relays and under frequency load shedding relays, leading to generation disconnection and unintentional load shedding. This can result in blackout. In this work energy storage system (ESS) is deployed in the two-area power system for improvement of short term frequency stability. A capacity optimization algorithm and dispatch scheme are developed for the ESS. The capacity estimation algorithm determines the required capacity of ESS. The proposed algorithm estimates the required capacity of energy storage while considering the complete dynamics of conventional generators, wind turbine, and power conversion systems. The dispatch scheme operates the ESS to inject the real power in the system to improve the short term frequency stability. The proposed methodology is verified in PSCAD. Simulation results depict the effectiveness of the proposed approach.