Variable susceptance excitation control for dynamic performance improvement of a stand-alone wind turbine induction generator system

Isolated wind farms employ simple squirrel cage induction generators driven by variable speed wind turbines. Lacking control capability, such generation can contribute very little to network support. Wind turbines mostly do not take part in voltage and frequency control and if a disturbance occurs, the turbines may be disconnected and reconnected when normal operation has been resumed. From operation viewpoint, this is definitely not acceptable. A primary reason for the rigidity of operation is the lack of excitation adaptation under variable wind conditions. This article proposes incorporation of a variable capacitance controller at the generator terminal which will automatically adjust the needed excitation. Further improvement of transient profile of the stand-alone wind turbine generator has been proposed through inclusion of additional stabilising control. Simulation studies show that the proposed excitation controller with additional PID circuit provides very good transient profile following reasonable input torque variations.