Power management of an isolated hybrid AC/DC micro-grid with fuzzy control of battery banks

Abstract

This study focuses on the development of a supervisory control scheme for power management and operation of an isolated hybrid AC/DC micro-grid, which consists of an AC micro-grid and a DC micro-grid. In the proposed hybrid micro-grid, wind and diesel generators and AC loads are connected to the AC micro-grid, whereas photovoltaic array and DC loads are tied to the DC micro-grid. Moreover, the authors consider two independent battery banks in the AC and DC micro-grids. Furthermore, the AC and the DC micro-grids are coupled through a bidirectional converter, which can act as an inverter or rectifier. The objectives of the proposed supervisory controller are listed as follows: (i) maximum utilisation of renewable energy sources along with satisfying the load power demand in both AC and DC micro-grids, (ii) maintaining state of charge (SOC) of battery banks in both AC and DC micro-grids and (iii) managing the power exchange between the AC and the DC micro-grids while the reliability of the whole system is taken into account. The supervisory controller is formalised using a state machine approach. For these purposes, 15 distinct operation modes are considered. Furthermore, in order to extend the battery life cycle, a fuzzy controller manages the desired SOC controlling the charge and discharge currents. The effectiveness of the proposed supervisory controller is evaluated through extensive numerical simulations.