A Modified Voltage Controller With Advanced Droop Control for Load Sharing in Standalone AC Microgrid Under Different Load Conditions

The limitations of traditional droop control-based decentralized methods for standalone microgrids, particularly the voltage drop caused by the loading effect, the droop effect, and the line impedance during load changes or disturbances, are currently being actively addressed by researchers. The main cause of these constraints is the instability of the system's operating voltage and frequency, which results in inaccurate load sharing among the standalone parallel AC microgrids. This article proposes a modified voltage controller employing advanced droop control (ADC) for load sharing in a standalone AC microgrid. The modified voltage controller (MVC) with filter capacitor current feedback to the outer voltage control loop and load current feed-forward as input to the inner current control loop enhances the system's dynamic response and the controller's effective bandwidth. Further, the proposed approach is independent of line impedance and allows precise load sharing among multiple standalone AC microgrids. Additionally, the current reference for auxiliary VSIs is set independently to take into consideration variations in local load. Therefore, local load variations have no effect on the frequency or voltage of the standalone AC microgrid. Extensive real-time simulation results and comparisons are carried out. The significant improvements in load sharing, voltage, and frequency stabilization under different load conditions over the MVC with traditional droop control are observed for several operating conditions, including the loss of the Primary VSI unit followed by the loss of the Auxiliary VSI unit in an individual standalone AC microgrid. The significant improvement in $\%$ THD of voltage and current is observed over the MVC with traditional droop control.