In order to obtain high transmission capability and avoid commutation failure, hybrid multi-terminal high voltage direct current (HVDC) transmission technology turns to be applied in actual power grid. Generally, rectifier station and inverter station are based on line commutated converter (LCC) and modular multi-level converter (MMC) technologies, respectively. Due to special structure of converter station and multi-terminal power grid topology, the travelling wave (TW) propagation process in star connected multi-terminal HVDC transmission system should be analyzed after DC fault happens to provide theoretical support for TW protection and fault location principles. Firstly, the TW reflection and refraction coefficients at converter stations are calculated. Secondly, the TW propagation characteristic is analyzed. Thirdly, to verify proposed theory, a typical ±400kV hybrid star-connected three-terminal LCC-MMC-HVDC simulation model is constructed based on PSCAD/EMTDC. And the simulation results prove the correctness of proposed theory.

hybrid,LCC-MMC-HVDC,multi-terminal,travelling wave