An adaptive grid-voltage sensorless interfacing scheme for inverter-based distributed generation

This paper presents an adaptive grid-voltage sensorless interfacing scheme for inverter-based distributed generation (DG) units based on an adaptive grid-interfacing model. First, a discrete-time model of a current controlled grid- connected inverter is presented. Second, an adaptive grid- interfacing model is designed with low computational demand to estimate, in real-time, the interfacing (impedance) parameters seen by the inverter and the grid voltage vector simultaneously. A reliable solution to the present nonlinear estimation problem is presented by combining a grid-voltage estimator with an interfacing parameter estimator in a parallel structure. Third, the estimated quantities are utilized within the inner high bandwidth current control loop and the outer power controller to realize an adaptive grid-voltage sensorless interfacing scheme. Theoretical analysis and evaluation results are provided to demonstrate the validity and usefulness of the proposed interfacing scheme.