Modified distance protection of transmission lines originating from DFIG-based WPPs by considering the impact of fault-induced rotor frequency and LVRT requirements

Abstract

This paper focuses on the protection of transmission lines connected to doubly-fed induction generator (DFIG)-based wind power plants (WPPs). DFIG-based wind turbines (WTs), which are connected to the AC grid via reduced-size converters, impose additional challenges on the reliable operation of distance relays due to their distinctive fault current characteristics, converter protective actions, and voltage or reactive control strategy of the converter. In this paper, a modified distance protection scheme is proposed which is able to reliably estimate the fault distance under the aforementioned challenges. The proposed scheme consists of two main components: phasor correction and fault resistance elimination. The phasor correction component eliminates the impedance error due to the fault-induced rotor frequency component of the DFIG short-circuit current. The fault resistance elimination component eliminates the impedance error due to the fault resistance during non-solid faults, which cannot be eliminated by conventional methods as a result of the variable nature of the equivalent impedance of the DFIG-based WTs during faults. Various simulation results are exhibited to validate the effectiveness of the proposed scheme in detecting and identifying all different types of faults on transmission lines emanating from DFIG-based WPPs.