Variable Structure Control of the Active and Reactive Powers for a DFIG in Wind Turbines

The original direct power control (DPC) is known to give a fast response under transient conditions. However, active power, reactive power, and current pulsations occur in steady-state operation. The variable structure control (VSC) method for a doubly-fed-induction-generator-based wind turbine system is presented, using the principles of an active and reactive power controller known as modified DPC and where VSC and space-vector modulation are combined to ensure high-performance operation. The VSC scheme is designed following the modified DPC philosophy, which provides robust and fast power controls without frame transformation and the current controller that is used in the conventional field-oriented control drive. Simulation and experimental results demonstrate that the proposed methods preserve the effectiveness and robustness during variations of active and reactive power, rotor speed, and converter dc-link voltage.