A Continuous Fault Ride-through Scheme for DFIGs Under Commutation Failures in LCC-HVDC Transmission Systems

Experimental and theoretical studies have confirmed that, relative to a one-shot voltage fault, a doubly-fed induction generator (DFIG) will suffer a greater transient impact during continuous voltage faults. This paper presents the design and application of an effective scheme for DFIGs when a commutation failure (CF) occurs in a line-commutated converter based high-voltage direct current (LCC-HVDC) transmission system. First, transient demagnetization control without filters is proposed to offset the electromotive force (EMF) induced by the natural flux and other low-frequency flux components. Then, a rotor-side integrated impedance circuit is designed to limit the rotor overcurrent to ensure that the rotor-side converter (RSC) is controllable. Furthermore, coordinated control of the demagnetization and segmented reactive currents is implemented in the RSC. Comparative studies have shown that the proposed scheme can limit rotor fault currents and effectively improve the continuous fault ride-through capability of DFIGs.