Low voltage ride-through augmentation of DFIG wind turbines by simultaneous control of back-to-back converter using partial feedback linearization technique

Abstract

This paper proposes a nonlinear controller for doubly fed induction generator (DFIG) wind turbines using partial feedback linearization (PFL) technique. The controller generates switching signals for driving both the rotor side converter and grid side converter simultaneously enhancing the low voltage ride through (LVRT) capability over a wide range of operating conditions. The proposed PFL method has been implemented into a partially linearized form of a nonlinear system, where the transformed system has been made autonomous and reduced in order. All calculations in the proposed method except for the control laws have been carried out offline resulting in reduced design and implementation complexity, small computational burden, and offline control tuning with fast tracking performances. The step-by-step approach of control design and implementation includes system modeling and partial linearization, control law derivation, software implementation, and controller tuning. The effectiveness of the proposed controller has been evaluated through electromagnetic transient simulations. The simulations have demonstrated that the controller has successfully augmented the LVRT capability of DFIG wind turbines and has remained robust against diverse wind conditions and voltage sags.