Time–Domain Distance Protection Scheme Based on Hybrid-π Model for Transmission Lines of Doubly Fed Wind Farm

Due to the controlled characteristics of fault current in doubly fed wind farms and the distributed capacitance effects of transmission lines, traditional distance protection is prone to failure or maloperation during high resistance faults. To improve protection reliability, this paper proposes a novel time–domain distance protection scheme based on the hybrid-π model. First, the improved time–domain fault differential equations are formulated based on the hybrid-π model, incorporating ground capacitance and integrating electrical quantities at both ends of the line. Next, the composite weight matrix integrating transient mutation weights and fitting error weights is introduced and embedded within a nonlinear least-squares framework. This enables the algorithm to adaptively distinguish and suppress unreliable data, simultaneously achieving transient disturbance resistance and rapid steady-state convergence. Finally, a 220 kV double-fed wind power grid-connected system with a 100 km transmission line is built in MATLAB/Simulink for simulation. Different types of faults under various locations and transition resistances are simulated to verify the effectiveness of the proposed scheme.