Detecting Faults in Doubly Fed Induction Generator by Rotor Side Transient Current Measurement

The doubly fed induction generator (DFIG) is one of the main technologies at variable speed power generation systems. Reliability and efficiency are key factors to realize the maximum energy output of the renewable resources. Detecting generator faults enables the reduction of risk for unexpected outages and thus high economic losses. Stator winding insulation faults count to one of the most frequent failures in electric machines. Common fault detection methods are based on several additional sensors and hardware what makes the system complex, expensive and also fault-prone. In this paper, a method is proposed and investigated to detect stator winding faults based only on measured signals available from inverter build-in sensors. By rotor-side inverter switching the generator is excited by transient voltage pulses and the current response provides the possibility to extract a fault indicator through a specific signal processing. Measurements on a DFIG test stand prove the methods applicability and accuracy.