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A new criterion to detect the stator single-phase-to-ground fault for Powerformer is proposed in this paper, which is based on the direction of leakage currents, magnitude of leakage currents, and fault point energy dissipation. New fault characteristics of Powerformer are analyzed and a novel criterion is put forward. The proposed approach detects the ground fault by analyzing the direction, magnitude, and energy of leakage current, which is the difference of zero-sequence current fault component between the neutral and the terminal of Powerformer. The fundamental component and the third-harmonic component of leakage current are combined to realize 100% coverage of fault detection for the stator windings of Powerformer. Simulation results have shown that, under different fault conditions, the new scheme can distinguish internal faults from external faults reliably, and can detect in which machine a stator single-phase-to-ground fault is occurring even if the fault resistance is at 5 kΩ. [ABSTRACT FROM PUBLISHER]

This paper focuses on the super/subsynchronous operation of the doubly fed induction generator (DFIG) system. The impact of a damping controller on the different modes of operation for the DFIG-based wind generation system is investigated. The coordinated tuning of the damping controller to enhance the damping of the oscillatory modes using bacteria foraging technique is presented. The results from eigenvalue analysis are presented to elucidate the effectiveness of the tuned damping controller in the DFIG system. The robustness issue of the damping controller is also investigated. [ABSTRACT FROM AUTHOR]