Applications of nonlinear control for fault ride-through enhancement of doubly fed induction generators

Applications of several nonlinear control laws, including differential geometric approach and the robust variable structure system (VSS) approach, will be investigated for the fault ride-through (FRT) enhancement of the doubly fed induction generator wind power system. In differential geometric approach, both input-output feedback linearization and state feedback linearization will be studied for rotor-side converter and stator-side converter control. In robust VSS approach, supplementary control generated by the complete models is achieved for FRT enhancement. Two objectives, maximizing the active power output as well as regulating the terminal voltage, will be utilized for designing the sliding manifold. Since the proposed methods are based on the general nonlinear system theory, the FRT capability can be indeed improved even under severe fault conditions. Simulations on a one-machine infinite bus system and a two-area four-machine system are presented to validate this result. Performance comparisons among several existing FRT enhanced control will also be examined to show the effectiveness of these nonlinear control schemes.