Neutral Current Compensation in a VSG-based Three-Phase Four-Wire Microgrid System

A three-phase four-wire system is commonly used on the customer side as a low-voltage power system for supplying universal single-phase loads. The degree of unbalance in the distribution system is growing due to interconnections of distributed energy resources unevenly in different phases. The unbalanced loads may cause an excess neutral current, which can result in the neutral conductor overload and power system security problems. In this paper, a control strategy based on the virtual synchronous generator with a neutral current controller is proposed. The controller enables the microgrid to operate under both grid-connected and islanded mode with the minimum neutral current. A microgrid built in Griffith University, Australia is used to verify the performances of the designed control algorithm. From the results, it is found that the proposed controller ensures smooth transition of microgrids from the grid-tied mode to the islanding mode, while regulating the active, reactive and unbalanced power efficiently.