Control Strategy for Islanded DC Distribution Network with High PV Penetration

Abstract

The extensive emerging of distributed PV power generation and DC loads accelerates the development of DC distribution network. In a DC distribution network, the intermittence of generation of distributed PV causes power fluctuation and the relatively large power load ratio weakens the PV utilization rate. In this paper, a control strategy for DC distribution network is proposed to solve the problems. The DC distribution network is connected to the main AC distribution network via a voltage source converter (VSC), and a battery storage system is employed to smooth the power fluctuation. In the grid-connected operation, the battery stabilizes the voltage of the DC distribution network while the VSC outputs constant power to the AC network. In the islanded operation, the battery controls the DC network voltage according to its state of charge (SOC) level. A new load shedding strategy is developed based on the DC voltage level to assure the power supply to the critical loads as long as possible. PSCAD/EMTDC is used for modeling and simulation. The simulation results verified the effectiveness of the proposed control strategy.