Analysis and Control of Energy Storage Systems for Power System Stability Enhancement

Utility-scale energy storage systems (ESSs) have been widely used in power system to facilitate its secure and economic operation. This paper investigates the transient influence of ESSs on bulk power systems. ESSs are treated as a controllable current source, whose dynamic response is represented by a first order transfer function. The influence of ESSs on the system dynamics is analyzed on a single machine infinite bus (SMIB) system with a ESS connected at its transmission line. The analytical result indicates that the deviated electrical power of synchronous machine (SG) caused by ESS is linear to both the d-axis and q-axis current of ESS. Based on this result, a control strategy of ESS's reference current is proposed to improve the system damping. Case studies are performed on both SMIB system and the 2-Area 4-Generator system to validate the correctness of the analysis and the effectiveness of proposed ESS control strategy.