A new relaying scheme for protection of transmission lines connected to DFIG‐based wind farms

Abstract

Abstract This paper presents a new protection scheme with low communication capacity requirement for protecting lines connected to a doubly‐fed induction generator (DFIG)‐based wind farm (WF). The proposed relaying scheme addresses the line protection challenges which stem from the non‐synchronous frequency component of the current fed from a DFIG‐based WF during a short‐circuit fault. The fault current frequency of a DFIG‐based WF deviates from the synchronous frequency during a fault, which affects the operation of distance relays. In such a scenario, the distance relay located at the WF terminal may lose its coordination with downstream relays, resulting in unnecessary tripping. The proposed scheme relies on the impedance trajectory captured by the local relay, local fault current characteristics, and the frequency tracking of the fault current measured at the distance relays located at the two ends of the transmission line connected to a DFIG‐based WF. The reliable performance of the proposed scheme is verified on a 4‐bus test system under balanced and unbalanced faults during super‐ and sub‐synchronous operating modes of the DFIG as well as its robustness against power system disturbances.

Keywords

• Wind power plants
• Asynchronous machines
• Power transmission, distribution and supply
• Power system protection