Effective power transfer and reduced-order generalized integrator sequence based fault ride through strategy in grid connected DFIG based WECS

Abstract

This paper deals with the control strategies of Doubly Fed Induction Generator (DFIG) based grid connected Wind Energy Conversion System (WECS) delivering power during normal and grid fault conditions. The system encompasses DFIG, Rotor Side Converter (RSC) and Grid Side Converter (GSC) connected back-to-back with a dc link, utility grid and local loads at point of common coupling. During normal system conditions, Tip Speed Ratio basedMaximum Power Point Tracking and Instantaneous Power Theory based reference current generation technique are employed for RSC, and GSC respectively to achieve maximum bidirectional power transfer and meeting the demand. Also, the power transfer operations during occasional conditions such as overloading and shorted stator winding are investigated. During grid fault conditions, a Reduced Order Generalized Integrator (ROGI) based Sequence Controller is employed to achieve stabilized real and reactive power injection to the grid by extracting the positive and negative sequence components of the grid voltages and currents. A supervisory control algorithm is developed for effecting a smooth transition of control schemes thereby avoiding system disturbances. The proposed control strategy is implemented in a simulation environment of a 10 MW grid connected DFIG based wind farm in MATLAB 2018b version. Various case studies are performed to validate the effectiveness of the proposed control strategies. The system is subjected to all possible grid faults including the most severe symmetrical fault and the controller is found to provide better grid support with appropriate real power transfer and reactive power injection. Also, the dynamic performance of the control strategy is experimentally investigated in the hardware setup of 1 kW grid connected DFIG based WECS. The system is operated under MPPT and FRT modes of operation under normal and grid fault conditions to prove the efficacious working of the proposed control strategies in DFIG based WECS.