Error compensation in distance relays caused by wind power plants in the power grid

• Prony method is proposed as a digital filter to obtain a better estimate of fundamental frequency phasors in distance relays.
• Prony method is implemented as a filtering technique as a solution of the apparent impedance measurement error.
• Impact in the fundamental frequency phasor estimates due to non-filtered frequencies in common digital filters is presented.
• A simplified model of a wind power plant is presented to perform transmission line protection analysis.
• Simulated and real fault event are presented to confirm that subharmonics/interharmonics are generated by wind power plants.

This article presents the Prony method as a filtering technique for distance relays. First, the effect of non-filtered frequency components generated by wind power plants in distance relays is evaluated in a simplified model of a doubly fed induction generator, resulting in an error of apparent impedance measurement. Then, the effects of non-filtered frequency components for typical distance relay are presented. The error in apparent impedance measurement is evaluated in reach and operation time of the relay; a distorted characteristic of the mho distance relay is shown in the impedance plane. Finally, Prony method as a filtering technique is implemented as a solution of the apparent impedance measurement error, and the simulated case and a real fault event are evaluated to validate the proposed distance relay algorithm. Thus the asynchronous frequency components of voltage and current signals are identified and filtered, as a result the performance of the distance relay is enhanced.