Anti-windup dual-loop control of DFIG under unbalanced voltage conditions

This paper proposes a new anti-windup dual-loop control of doubly-fed induction generator (DFIG) under unbalanced grid voltage conditions. System behavior and controller operation of windup under unbalanced conditions are illustrated. To avoid the windup problem, a new extraction method based on Discrete Fourier Series (DFS) is proposed to decouple the sequence components indifferent to sub- or super- synchronous operation of the DFIG system. A dual loop control is developed for the decoupled positive and negative sequences. The positive sequence control loop is responsible for the conventional torque control and the additional negative sequence control loop is responsible for the minimization of 2^nd harmonic in torque pulsation and dc link voltage fluctuation. Simulation results using Matlab/SimPowerSystems library are presented for the built-in single loop and modified dual-loop 9 MW DFIG wind generation systems under unbalanced grid voltage condition to demonstrate the system operation and validate the proposed dual-loop control scheme.