A Novel Pilot Protection Scheme for Wind Farm Transmission Line Based on Harmonic Content Ratio

Influenced by the unique structure and the complicated control strategies of the doubly fed induction generator (DFIG), the short-circuit current supplied by a DFIG has the frequency offset characteristics and contains a large number of harmonics, which pose challenges to the protection scheme based on the phasor measurement in the wind farm transmission line. To deal with these issues, a novel pilot protection scheme based on harmonic content ratio is proposed in this paper. Firstly, the frequency spectrum difference between the short-circuit current at system side and at the wind farm side is analyzed. Secondly, the harmonic content ratio is constructed using the Prony algorithm and a novel pilot protection scheme is proposed accordingly. With the harmonic content ratio as the main criterion and the harmonic attenuation ratio as the auxiliary criterion, the proposed scheme is suitable for the wind farm transmission line protection and can solve the performance degradation problem of the power frequency phasor based protection. The simulation results verify effectiveness of the proposed scheme.