Comparison of Active Damping Systems for the Doubly-fed Induction Generator

The doubly-fed induction generator (DFIG) is characterized by two poles near the imaginary axis on the complex plane. This leads to poorly damping oscillations. To damp these oscillations several methods can be used. This paper compares, using a detailed simulation program, four active damping systems that inject on the rotor a damping current in order to damp stator-flux oscillations. The purpose is to evaluate which damping method provides the best damping using less additional rotor current. For damping transients originated on the stator, e.g. voltage dips, all the methods analyzed need high values of rotor damping current. The two axis damping method that uses variations of state variable is the method that uses lower values of rotor current for the same damping action.