A voltage perturbation control of VSI with estimator in weak microgrid

This paper presents a voltage perturbation control strategy in weak microgrid, which is able to use a voltage estimator to perform voltage feed-forward control. The proposed control strategy is embedded in voltage source inverter (VSI) and provides supplementary control in power-voltage control system. When a series of parameters perturbation occur, the output voltage waveform of VSI would be distorted, at the same time, the amplitude error and the phase error as compared to microgrid voltage would appear. As the amount of perturbation cannot be obtained directly through measurement, an estimator is used to calculate this perturbation in order to realize feed-forward compensation for the perturbation component. Finally, VSI output voltage amplitude, frequency and phase are the same as those of microgrid at the point of common coupling. Therefore, the distributed generator through VSI can be connected without phase locked loop. Furthermore, the robustness of the control system is investigated under parameters´ variation. The simulation and experimental results show that the smooth transition is achieved when a DG is connected or disconnected from the islanded microgrid.