Protection of Doubly Fed Induction Generator-Based Wind Turbines Against Loss of Excitation of the Rotor Winding

The doubly fed induction generator-based wind turbine (DFIG-WT) has an excitation system in the rotor winding (RW), provided from the machine terminal through a back-to-back converter which may be lost partially and/or completely due to the fault in the rotor-circuit. Accordingly, this article outlines a novel protection system for DFIG-WT against loss of excitation (LOE) of the RW. For this purpose, two parameters of the reactive power (Q(s)) and DC-link voltage (V-dc) have been comprehensively analyzed theoretically and through typical simulation studies. The results show that, although they have the potential for detecting the complete LOE (CLOE), the partial LOE (PLOE) cannot be detected by means of them. Hence, to precisely detect the CLOE, the derivative of multiplication of the parameters has been implemented. On the other hand, further exploration to find the suitable parameter to address the PLOE show that, the stator current (I-sr) considering the proper settings, can be the most suitable indicator. The results from evaluation of the developed algorithm on a typical test system in MATLAB/Simulink (2017b) environment show its reliability and swiftness in addressing the LOE events.