Dynamic Performance Of DFIG Based WECS Under Different Voltage Sag

At the present time Doubly Fed Induction Generator (DFIG) based wind energy conversion systems are widely used for large wind power plants. DFIG offers many advantages for instance reduced rating power converter, low cost and reduced losses with the better efficiency, easy in realization of power factor correction schemes, variable speed operation and four quadrants active and reactive power control capabilities. Due to operate under variable speed mode total energy output is much more, so capacity utilization factor is enhanced and cost of per unit energy is cheap. But the main disadvantage of DFIG is that it is very susceptible to grid disturbance or fault, particularly for the voltage dip. As the doubly-fed induction generator (DFIG) has been broadly used in wind energy conversion systems, the Fault Ride through (FRT) or Low Voltage Ride through (LVRT) expertise of the DFIG has been investigated extensively in recent times. This paper focuses the fault ride-through capability of DFIG based WECSs under different voltage sag. The paper also gives an overview on the interaction between variable-speed DFIG based WECSs and the power system subjected to disturbances/fault. The dynamic performance of WECS based on DFIG under grid faults is simulated and assessed. This paper also discusses major grid problems and grid codes for operation & grid connection of wind farms and gives brief introduction about the solutions for FRT/LVRT available in market today.