Control Strategy for Smooth Switching and Off-Grid Stable Operation of Multi-energy Complementary Microgrid

Abstract

Smooth and seamless switching and off-grid stability control of muti-energy complementary microgrid is an important guarantee for independent power supply of the critical load. In combination with the practical situation of a demonstration plant, a MW multi-energy complementary microgrid simulation model is established in this paper integrating photovoltaic, gas turbine and battery energy storage. Six energy storage systems are controlled by group. Master–slave control is adopted in off-grid, and the master battery energy unit is switched to droop control. The negative feedback is added to traditional droop control to improve the stability of the output voltage and current. When the normal load is cut off from the grid, a multi-source coordinated load shedding strategy of load cutting by stages is proposed on the basis of coordinating the slave energy storage output, which reduces the transient impact of power imbalance during the off-grid switching process. Then, the power supply of normal load is restored by connecting with gas turbine. In the case of sudden load change, the power supply of battery storage can be scheduled in advance through load forecasting to ensure the stability of independent power supply. Finally, the effectiveness of the proposed strategy is verified by simulation to ensure the independent and uninterrupted power supply of the critical load.