Protection and Control Switching Research on Hybrid Microgrid DC Distribution System

Abstract

This paper proposes a control strategy for smooth switching between grid-connected operation mode and off-grid operation mode based on the AC-DC hybrid microgrid scenery storage integration model for the unplanned off-grid situation. First, in the case of grid-connected operation mode, the interconnection converter adopts PQ control strategy; in the case of off-grid operation mode, a V/f control strategy is adopted, as the operating state changes, the control strategy is changed simultaneously to achieve the optimum control effect for the respective operating mode. At the same time, pre-synchronous control is used when switching from islanded to grid-connected operation. In this paper, the control method and theoretical analysis are studied and given for the special condition, such as the sudden change and uncertainty of unplanned off-grid, and finally, the method proposed in this paper is experimented through simulation to verify its feasibility and effectiveness.