Improved LVRT based on coordination control of active crowbar and reactive power for doubly fed induction generators

Abstract

This paper proposes a control system, for crowbar protection and voltage support, for wind turbines equipped with doubly fed induction generator. The control system based on PI controller enables the low voltage ride through capability of the wind turbines. The reactive power control of doubly fed induction generators is mostly achieved by controlling its rotor side converter. The proposed control system allows regulating the reactive power using the rotor side converter as well as the grid side converter. During crowbar activation, the rotor side converter can no more control the reactive power. The proposed system controls the voltage at the point of common coupling to be above the imposed low voltage ride through curve, until the grid side converter returns to normal operation. The proposed models were implemented in Matlab/Simulink. The case studies refer to a control system with hysteresis band for the crowbar protection of a 3MW doubly fed induction generator based wind turbine. The simulation results highlights that the proposed control improves the coordination between grid side converter, rotor side converter, and crowbar protection.