A Single-ended Fault Detection Method Based on Active Boundary Control in Weak or Non-Boundary Scenarios

With the improvement of power electronic equipment, boundary components are gradually weakened or even eliminated, making it difficult to realize fault identification across the whole line solely based on single-ended electrical characteristics. Therefore, this paper introduces the concept of active boundaries, leveraging the high controllability of power electronic equipment to develop virtual diversion and suppression controls. These controls can help to amplify the differences between internal and external faults, effectively mitigating protection dead zones at the terminal of the line. Additionally, using the refraction coefficient as an indicator, the influence of equivalent resistance, inductance, and capacitance parameters of the converter is analyzed. Building on this, the energy ratio of high to low frequency band criterion considering frequency information is proposed to achieve single-ended whole-line protection in power electronic systems. The proposed scheme is validated using a multi-terminal hybrid HVDC transmission system model. Simulation results demonstrate that even in weak or non-boundary scenarios, the scheme can accurately identify faults across the whole line without relying on communication or coordination with other protection schemes, while maintaining high sensitivity and reliability.