Pilot protection scheme for transmission line of wind-storage combined system based on one-mode current similarity.

• Proposed a protection scheme can determine the fault type only by calculating the similarity of one-mode current. • Based on the principle of one-mode current similarity, offering a viable solution to address the challenges arising from weak-infeed, frequency offset, and phase uncertainty caused by the LVRT strategy of the new energy station. • Proposed a protection scheme has good adaptability when the wind farm operates independently, and can also adapt to different wind farm capacity and energy storage ratio, which has certain application prospects in practical engineering. With the gradual growth of the scale of energy storage devices for wind power generation, a large-scale grid-connected wind-storage combined system (WSCS) has been formed. When the external transmission line fails, its control strategy will lead to problems such as limited output short-circuit current amplitude, frequency deviation from power frequency, and uncertain phase angle, which makes the traditional pilot protection possible to malfunction and refuse to operate. In order to solve this problem, this paper first analyzes the fault current output characteristics of the WSCS during low voltage ride through (LVRT), and its impact on the traditional pilot protection scheme. Secondly, considering the difference of fault current amplitude and phase change at both sides of the transmission line, the similarity relationship of one-mode current is verified. Finally, a pilot protection scheme based on one-mode current similarity is proposed in this paper. The simulation results conducted using PSCAD/EMTDC demonstrate that the proposed scheme exhibits robust anti-interference capability, capable of withstanding significant transitional resistance and noise, while maintaining good selectivity and reliability. [ABSTRACT FROM AUTHOR]