Selective Compensation of Current Harmonics in Grid-Connected Doubly-Fed Induction Generator based Wind Energy System

This paper presents a new approach for simultaneous selective compensation of current harmonics and reactive power compensation in grid-connected doubly-fed induction generator (DFIG) based wind energy system. The proposed control algorithms are applied to the DFIG with a stator directly connected to the grid, and the rotor connected to the grid through a converter with a bi-directional energy flow. Depending on the power of the converter, the power quality can be improved by compensating the reactive power and harmonics of the grid current. It is proposed to use the observer based scheme to estimate current harmonics of the nonlinear load. This task is performed in a d-q reference frame where active and reactive current components are obvious. Positive and negative sequences are distinguished for selective compensation. Simulation results for a 2 MW DFIG confirm the effectiveness and the performance of the proposed approach.