Research on the Control Strategy of Multi-Machine Parallel Operation of Grid-Forming Energy Storage Based on Droop Control

With the development of new energy and power electronics, the new power system presents typical “double high” characteristics, and brings low inertia, weak stability and other problems. In order to improve the support ability of energy storage system in weak grid environment, an improved droop control strategy based on three-phase independent control is proposed. Firstly, aiming at the application of traditional droop control methods of frequency active power and voltage reactive power in unbalanced system, the single-phase droop control curve is formed by calculating the power and voltage frequency of each phase to solve the problems of voltage imbalance and phase to phase circulating current. The pre synchronous startup strategy is adopted to meet the requirements of any host startup of multiple machines and solve the problem of impulse current generated during the startup of each energy storage converter. Finally, an empirical system is built to verify the effectiveness of the proposed control strategy.