Power Control of DC Microgrid Using DC Bus Signaling

DC microgrid is an effective solution to integrate renewable energy sources with conventional utility grid, especially for photovoltaic generation. A DC microgrid configuration based on modular photovoltaic generation system and energy storage devices, which features good redundancy and high efficiency, is investigated in this paper. In order to optimize energy utilization, a power management scheme for DC microgrid is proposed, which consists of four operation modes. The DC bus voltage level is employed as an information carrier to distinguish different modes. Control methods of modular PV converters, battery converter and grid-connected converter are addressed. An automatic control method for modular PV converters is proposed to realize smooth switching between constant voltage operation and MPPT operation, which enables the DC bus voltage regulation capability of modular PV converters. This control method maintains the power balance of DC microgrid under extreme conditions such as the islanding mode with full-charged batteries. Experiments verify the practical feasibility and the effectiveness of the proposed control strategies.