Performance Investigation of Hybrid AC/DC Microgrids during Mode Transitions

The hybrid AC/DC microgrid is getting popular in different countries including Australia as it could enhance energy efficiency and system's reliability. This paper investigates the dynamic performance of a hybrid AC/DC microgrid during transition from grid-tied mode to isolated mode and vice versa. As the droop control method allows the system to operate under both grid-connected mode and islanded mode, it is adopted as the main inverter control strategy for observing the system's performance during mode switching. Different characteristics of distribution energy resources (DERs) make it complicated to share power between the DC subgrid and the AC subgrid during islanded mode. Therefore, this paper investigates the performance of a hybrid microgrid under different scenarios which contains various DER combinations. DER units such as PV modules, wind turbines, battery energy storage systems (BESSs), and micro-turbines are utilized for building systems with different structures. Different case studies are carried out in MATLAB/SIMULINK environment based on a real microgrid system which is built in Griffith University Nathan campus for demonstrations. Simulation results show that the microgrid system could perform well and ensure smooth transition with the proposed control strategy described in this paper. Through the comparisons of different scenarios, it can be seen that system which include BESS could show better performance during mode transition. When micro-turbine involves in power supply, fluctuations in AC voltage and power supply can be optimized.