Closed-loop control impact on the detectability of stator high-resistance connection in Doubly-fed WRIMs based on rotor power spectral analysis

Design of modern Wind Energy Conversion Systems (WECSs) must take into account two crucial aspects: efficient control strategies and reliable monitoring and diagnosis techniques. Wind turbine generators based on Wound Rotor Induction Machine (WRIM) is actually the preferred technology mainly because of the lower rating of the power converter connected to the rotor side. With the association of a back-to back converter on the rotor side a Stator-Flux-Oriented-Control (SFOC) system can be used to obtain a decoupled control of the active and reactive power on the stator side with high efficiency. In this context, the influence of the Closed-Loop (CL) control scheme must be considered when the diagnosis of stator asymmetry is derived from the signature analysis of electrical quantities. Therefore, an examination of the spectral content of the investigated quantities for different bandwidths of CL regulators is necessary to assess the effectiveness of the derived fault indexes. In this paper, the performances of three different techniques based on rotor electrical quantities, for detecting stator asymmetry are investigated. Results with numerical simulations and experimental tests are here presented showing the validity of the established comparative study.