A visually driven nonlinear droop control for inverter-dominated islanded microgrids

Abstract

The network asymmetries have led to the conventional droop methods that have significant reactive power sharing error during islanding operation of a microgrid. That is why the expandability, modularity, flexibility and communication-free nature of droop-based methods do not let the researchers to easily replace them with another kind of solution. Accordingly, this paper proposes a visually driven nonlinear droop curve making it possible to improve the reactive power sharing accuracy. Of course, due to the probability of the voltage drop at the output terminals of distributed generations, a voltage restoration mechanism should be also presented to maintain the voltage within an acceptable range. In this way, the proposed method can successfully improve both the reactive power sharing accuracy and voltage profile even during fault conditions. Both simulation and experimental case studies using various scenarios are conducted to demonstrate the merits of the proposed scheme. According to the obtained results, the proposed scheme ensures the voltage regulation of MG buses at all times. For instance, the accuracy of reactive power sharing in heavy load conditions has been increased to 96.5% which indicates 21.2% increase in comparison with the conventional droop strategy.