An autonomous control scheme for DC micro-grid system

This paper presents an autonomous control scheme for DC micro-grid system both in grid-connected and islanding conditions. The proposed DC micro-grid architecture consists of a wind turbine generation unit, a photovoltaic generation unit, two battery stack units, a grid-connected inverter/rectifier and loads. Corresponding control strategy of each unit is presented. DC droop control method is adopted into voltage control loop to suppress the circulating current when two or more voltage sources are connected to DC bus. The energy that flows through each unit and different operating modes of the system both in grid-connected and islanding conditions are analyzed. Power management method to balance the energy of the system and stable the DC bus voltage is presented. Simulation results verify the effectiveness of the proposed control scheme in various operating conditions.