Fault Analysis and Traveling Wave Protection Based on Phase Characteristics for Hybrid Multiterminal HVDC Systems
Yuansheng Liang, Liantao Jiang, Haifeng Li, Gang Wang, Qing Zhong, Longjun Wang
Abstract
By fully combining the advantages of line commutated converter (LCC) high-voltage direct current (HVDC) and modular multilevel converter (MMC)-HVDC systems, hybrid multiterminal HVDC (hybrid-MTDC) transmission technology has become a new technical means to overcome the shortcomings of conventional two-terminal HVDC systems. However, the conditions of high fault resistances and more sophisticated network topologies have brought considerable challenges to the existing traveling wave (TW) protection principles. In this article, a parallel hybrid-MTDC system is taken as the research object, and its mathematical analysis model is established. Based on the mathematical model, the TW characteristics that the phase of the high-frequency voltage TW during the occurrence of an internal and external fault approaches approximately 90° and 0°, respectively, are clarified. Therefore, considering the influences of reflection and refraction of TWs and line propagation, the phase-characteristics-based criterion is constructed. Using the proposed criterion, a protection scheme for hybrid-MTDC systems is proposed, which realizes the identification of line faults with high fault resistance. The proposed method is verified in detail with the electromagnetic transient simulation model using PSCAD/EMTDC, and the test results show that the proposed protection scheme is feasible and has high sensitivity, reliability, and adaptability to different operation modes.