A control scheme for voltage unbalance compensation in an islanded microgrid

One of the major power quality issues in low-voltage (LV) microgrids is the voltage unbalance which has adverse effects on electrical devices. This paper presents a novel control scheme to mitigate the voltage unbalance by a photovoltaic (PV) system. In this study, load current sensors are eliminated and the PV system mitigates the voltage unbalance by analyzing its terminal voltage. This could effectively reduce the cost and complexity of compensation system because of the difficulties of load current sensors. The proposed control strategy is developed for a three-phase PV. As the inverter detects the voltage unbalance at its terminal, the proposed control algorithm calculates the compensation reference currents based on the double synchronous reference frame (DSRF) analysis of the PV terminal voltage. Therefore, the PV inverter injects the compensating currents to the microgrid. The effectiveness of the control scheme is verified by simulation studies in the PSCAD/EMTDC environment.