A Novel Adaptive Current Differential Protection for Wind Farms Based on Cosine Compensation Coefficient

The integration of doubly-fed induction generators (DFIGs) into wind farms presents significant challenges to current differential protection (CDP). In this study, an adaptive CDP principle for wind farms is proposed. By introducing the virtual restraint current, the restraint current is significantly reduced under low-resistance faults. Additionally, a boundary model is constructed based on the complex relationship of current phasors. On this basis, the cosine compensation coefficient is formulated solely using the amplitudes and phases of the two-terminal currents, which further enhances the ability to identify high-resistance faults. The principle can also lock the restraint coefficient according to the current amplitude, thereby reducing false trips. Finally, the performance of the scheme is demonstrated by Hardware-in-the-loop (HIL). Test results indicate that the proposed principle identifies faults more reliably and rapidly than the conventional CDP. The proposed principle is novel and feasible both in theory and practical applications.