Assessment of conventional HVDC line protection methods for modular multilevel converter based HVDC line

Abstract

The Modular Multilevel Converter (MMC) HVDC system is becoming increasingly significant in contemporary power grids as power electronics technology continues to evolve. It is essential to provide protection in large DC circuits to maintain stability and security during faults. This paper presents a comparative analysis of the travelling wave-based protection schemes of PMGMW and CBTW, which were originally developed for LCC HVDC systems and have been adapted for a two-terminal MMC HVDC system. In order to assess fault resistance endurance, fault identification accuracy, and processing time under a variety of fault conditions, simulations were conducted in PSCAD/EMTDC. The results suggest that Pole Mode Ground Mode Wave’s (PMGMW) scheme is more resilient to high resistance faults, maintaining accuracy at fault resistances of up to 100 Ω, while  Change in Backward Travelling wave’s (CBTW) scheme is less resilient to high resistance faults but demonstrates quicker fault identification with reduced processing time.  Consequently, this investigation further solidifies the insights into the improvement of current protection systems for MMC HVDC applications.