A hybrid AC/DC micro-grid

This paper proposes a hybrid AC/DC micro-grid which consists of an AC grid and a DC grid and operates in both grid-tied and autonomous mode. Wind turbine generators (WTGs), diesel generators (DGs) and conventional AC loads are connected to the AC grid whereas photovoltaic arrays with boost converter (PVBC), fuel cell generators and DC loads are tied to the DC grid. AC bus and DC bus are coupled through a four-quadrant operating three phase converter which can act as an inverter or rectifier. Battery is connected to the DC bus through a charging/discharging converter to maintain energy requirement when the system operates in the isolated operation mode. A prototype of the hybrid system has been established and simulated using Matlab Simulink. The coordination control algorithms are proposed to balance power flow between AC and DC grids and to maintain both DC and AC voltages. Uncertainty and intermittent characteristics of wind speed, solar irradiation level, ambient temperature and load capacities are also considered in system control and operation. The simulation results show that system is stable under various load and supply conditions. Moreover, the hybrid grid has higher efficiency than individual DC or AC micro grid due to avoidance of multiple DC-AC-DC conversions.