DFIG Based Wind Turbine Protection Using Active Crowbar and SVC during Grid Faults

Abstract

This paper addresses the protection schemes that improve the dynamic performance of the grid that has a Doubly Fed Induction Generator (DFIG) based wind turbine, during balanced and unbalanced grid operating conditions. Faults in power grids can lead to sudden drop in the grid voltage at the connection point of the DFIG based turbine. This can also cause over current in the rotor windings and over voltage in the power converters. Without proper protection, power converters may be subject to damage and the turbine may suffer over speeding, which may lead to unsafe operation. Furthermore, following fault clearance, the wind turbine shaft experiences an oscillating torque, which can severely stress the turbine shaft leading to a shut-down of the wind turbine as a protection measure. Hence, protection devices are used, including active crowbar and Flexible AC Transmission Systems (FACTS) devices, such as Static VAR Compensator (SVC), to protect the DFIG based wind turbine interconnected grid from isolation. This research work compares the system performance when using active crowbar technique and SVC for the protection of DFIG from voltage dips which occur following faults. Simulation are obtained for various operating conditions to validate the reliability of the proposed techniques. Results shown verify the validity of both techniques, with better results obtained in case of using SVC.