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With increasing penetration of wind energy into the power grid, researchers have started focusing more on control and coordination of wind energy conversion systems (WECS) with the other components at system level, especially during fault. It is important to implement a suitable fault ride through control strategy to avoid tripping of the generators when the power system is subjected to voltage dips normally below 90% of nominal voltage. The dips below 90% may lead to a significant loss of generation and frequency collapse, followed by a blackout. This article implements and assesses the methodologies to deal with such situations for squirrel cage induction generator-based wind energy conversion systems employing fully rated power electronic converters. Three distinct control techniques-namely, balanced positive sequence control, positive negative sequence control, and dual current control-have been simulated and applied to grid side converter of SCIG-based WECS. The performance of all the three control strategies has been compared and presented in this work. During this study, the system is subjected to the most common unsymmetrical line to ground (LG) fault and most severe symmetrical LLL fault on grid for the purpose of anaysis. ARTICLE HISTORY

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Strict environmental regulations and shrinkage of fossil fuel supplies necessitate the generation of electricity by using renewable energy sources. Most promising and popular source of green electricity is wind energy. WECS using DFIG is a meritorious option as it uses back to back power converters at a reduced rating, offers high controllability, allows maximum power extraction and individual control of active and reactive power components. Various performance indices like operation, control of power, cost and necessity of fault ride through are discussed in the available literature, which speaks very less on dynamic behavior of WECS using DFIG. In this work, an analysis based on the behavior of DFIG based WECS during symmetrical as well as unsymmetrical faults is presented. The analysis is performed to perceive the behavior of WECS under varying wind velocities or for below-synchronous and abovesynchronous speeds of generator. A brief review on fault ride through capability enhancement of these systems is also presented.