Transient Overvoltage Analysis of DC Line Faults in Renewable Energy Grid-Connected HVDC Transmission System

With the increasing integration of renewable energy via line-commutated converter high-voltage direct current transmission, low short-circuit ratio sending-end systems are prone to transient overvoltage due to reactive power surplus following DC line faults, jeopardizing the grid-connection stability of renewable energy units. To address the limitations of existing approaches in dynamically characterizing transient behaviors and enabling real-time applications, this paper proposes an online time-domain calculation method for transient overvoltage response under DC line faults. A dynamic model of the sending-end system is developed, incorporating the control dynamics of renewable energy units and their interaction with LCC-HVDC. By integrating optimized initial value selection and numerical solutions of differential equations, the method enables rapid computation of post-fault node voltage time-domain profiles. The proposed approach accurately computes transient overvoltage time-domain curves and extracts critical metrics such as peak magnitude. Simulation results demonstrate that the method significantly outperforms conventional steady-state methods in both dynamic accuracy and computational efficiency, offering a theoretical foundation for real-time emergency control strategy formulation in renewable energy stations.