Stabilizing the VSI response in microgrids via novel PI controllers

摘要

In distributed generation and modern smart grids, the voltage source inverter (VSI) is commonly used as a basic interface between the different power sources and devices. The control capabilities of the VSI are very essential in transforming the passive distribution network into an active one. In this frame, the modeling, control and stability analysis of a VSI, standing as an interface between a dc current source and a three-phase voltage grid, is investigated. Adopting the mean value model of the VSI in the synchronously rotating d-q reference frame, a pair of simple cascaded mode controllers are proposed to locally regulate the reactive power and the dc voltage, respectively. As shown in the paper, stable inner-loop current controllers can be of simple proportional-integral (PI) form with damping, which are fully independent from the system parameters; the outer-loop voltage and power controllers are also of simple PI type. Hence the paper focuses on presenting the detailed nonlinear analysis needed for proving stability of the VSI with the proposed controllers incorporated. Finally, the theoretical results are further verified by extended simulations.