Multi-Terminal Hybrid UHVDC Line Protection Scheme

The hybrid ultra-high voltage direct current (UHVDC) system is composed by line commutated converter (LCC) and voltage source converter (VSC). And the multi-terminal hybrid UHVDC system which can provide a larger capacity, more economical and more flexible transmission mode, is a development trend of HVDC technology. The system proposed in this paper adopts VSC converters with the characteristics of DC fault self-clearing and high speed switch (HSS). The DC line protection scheme of multi-terminal hybrid UHVDC system is investigated. First, the configuration scheme of DC line protection and and coordination strategy are proposed. Then, aiming at the key problem of line fault isolation in this multi-terminal system, the fault line selection method is proposed. Finally, based on PSCAD/EMTDC simulation, the feasibility of the proposed fault line selection method is verified.