Fast power correction based transient frequency response strategy for energy storage system in low-inertia power systems

Energy storage system based on grid forming control (ESS-GFM) plays a crucial role in future low-inertia power systems, which can offer frequency support and enhance frequency stability. Despite its significance, the interaction between ESS-GFM and the low-inertia power system is not well understood, limiting ESS-GFM to improve the hybrid system frequency response. To address this issue, this paper models the dynamic response of ESS-GFM and low-inertia power systems with a uniform form of the swing equation, which can probe the factors that determine the frequency response of hybrid system. Therefore, a fast power correction (FPC) based transient frequency response strategy is proposed to enhance frequency stability of hybrid system. Firstly, the fundamental principle of the FPC strategy that controls the output power of the ESS-GFM to the maximum allowable value to provide the optimal frequency response is given. Secondly, the mode transition logic and detailed implementation of the FPC strategy are provided to handle different operational requirements. Finally, it is verified through two-converter experiment and multi-machine system simulation that the FPC strategy can reduce the frequency deviation by 57% and the rate of change of frequency by 41%, respectively.