An Under-Frequency Load Shedding Method Adaptive to the Islanding Operation of Micro-Grids

A new control strategy is proposed, in which a closed-loop frequency control circuit is composed by PID controller and the PID algorithm should be adjusted according to the power shortage of power grid and the control strategies for under frequency load shedding (UFLS) such as rough-adjusting step, fine-adjusting step and emergence pick-up step are adopted respectively. The UFLS control strategy for emergence pick-up step can improve system stability and reliability of micro-grid; and the UFLS control strategies for rough-adjusting step, the fine-adjusting step can adapt to various power shortage and the load amount could be deliberately divided. Simulation results show that the proposed method is effective.