Coordinated Fault Ride through Strategy for SCIG Based WECS

Wind technology is one of the fastest developing renewable technologies. Squirrel cage induction generator (SCIG) with back to back fully rated converter used for wind energy conversion systems (WECS) is a meritorious option among its class. SCIG's offer advantages of being robust, suitable for any harsh environment, cheaply available and unsophisticated than the other types available. To enable increased share of wind energy in the grid without compromising power system stability, the generator ought to stay connected and continue to feed the grid even in case of disturbances such as voltage sag. This paper presents a coordinated control scheme to address the fault ride through of SCIG based WECS. A WECS based on SCIG having back to back connected voltage source converters involving Rotor flux oriented vector controlled drive at machine side and hysteresis current controlled inverter for grid interface has been simulated in MATLAB/SIMULINK. Abnormal rise in dc link voltage during symmetrical faults is controlled by de-loading control while positive-negative sequence control is used for real and reactive power control during symmetrical and unsymmetrical faults. During this work, coordinated performance of all the above stated control strategies during most severe symmetrical (LLL) and most frequently occurring unsymmetrical (LG) fault has been examined.