A Quasi-Disturbance Current-Based Droop Control Strategy for Enhancing Voltage Robustness of Islanded AC Microgrid

The voltage distortion caused by the nonlinear load seriously threatens the safe and stable operation of the droop control-based islanded ac microgrid. To address this issue, a quasi-disturbance current-based voltage robustness control strategy of the inverter-based distributed generator (DG) is proposed, which does not need any filters to extract harmonics. By feedforwarding a quasi-disturbance current in current loop, the voltage robustness of the islanded ac microgrid can be significantly enhanced under load disturbance. In addition, based on the impedance method, the impedance model of the improved DG is built and the voltage robustness of the islanded ac microgrid is analyzed from the perspective of impedance. In the middle-frequency band, the impedance of the DG controlled by the proposed control strategy is obviously smaller than that of the classical DG, which makes the optimized DG more like an ideal voltage source and thus improves the voltage robustness of the islanded ac microgrid. Compared with the traditional harmonic suppression methods, the proposed method is simpler and can suppress time-varying harmonics in the middle-frequency band. Finally, the theoretical analysis and the proposed control strategy are verified with the simulation and experimental study.