An HVDC System Based on OWT-DMMC With DC Fault Ride-Through Capability

Abstract

High voltage direct current (HVDC) systems using modular multilevel converters (MMC) have seen significant deployment in modern power systems. To achieve dc fault ride-through (FRT), traditional solutions typically involve either the use of dc circuit breakers (DCCBs) or specialized MMC topologies with complicated submodules (SMs), both leading to high system costs. This paper introduces an HVDC system based on a novel MMC topology, which is called open-winding transformer-based dual modular multilevel converters (OWT-DMMC). By leveraging the unique structure of OWT-DMMC, it can achieve dc FRT using exclusively half-bridge SMs. Further, it facilitates fault-tolerant operation, allowing continuous power transfer during dc faults. The effectiveness of the OWT-DMMC-based HVDC system is confirmed through PSCAD/EMTDC simulation and hardware-in-the-loop test results. Cost and loss analyses show that the proposed method can offer significant economic advantages over existing methods for short-distance applications.