Travelling wave directional pilot protection for hybrid LCC-MMC-HVDC transmission line

Abstract Currently, line commutated converter (LCC) and modular multilevel converter (MMC) based hybrid high voltage direct current (HVDC) is applied in actual power transmission system. Generally, LCC-MMC-HVDC transmission line adopts travelling wave (TW) protection as primary protection which includes voltage change criterion, voltage change rate criterion and current change rate criterion. In fact, it has threshold issue and no fault direction discrimination ability which could lead to wrong operation to external fault. Besides, it has not considered different structures of LCC rectifier station and MMC inverter station. In order to overcome these disadvantages, the paper proposes a novel TW directional pilot protection for hybrid LCC-MMC-HVDC transmission line. Firstly, special TW propagation process characteristic in hybrid LCC-MMC-HVDC transmission system is analyzed. Secondly, a novel fault direction discrimination algorithm and complete implementation scheme are proposed. Thirdly, using PSCAD/EMTDC, a ± 400 kV hybrid LCC-MMC-HVDC transmission system simulation model is established. Eventually, a series of simulations prove that the proposed TW protection actions correctly with different fault locations, different fault resistances and different fault types.