DC fault ride-through method for full-bridge MMC-based MTDC systems

Abstract

The DC fault protection is one of the main issues in multi-terminal voltage source converter based high-voltage direct current (VSC–MTDC) transmission systems. In this study, a DC short-circuit fault ride-through method for full-bridge modular multi-level converter (FB-MMC) based MTDC systems is proposed. First, the model of the FB-MMC topology is analysed. Then, the principle of fault current clearing in full-bridge sub-module (FB-SM) is introduced. The converter protection control strategy and the system protection scheme are proposed, benefitting from the capability of quick fault current elimination with the valves blocked using the FB-MMC topology. With this method, the MTDC system could restart quickly after clearance of DC fault without cutting off the AC grid. The proposed protection strategy is demonstrated using the simulation model in PSCAD/EMTDC. Simulation results verify the feasibility and effectiveness of the strategy.

Keywords

• power grids
• HVDC power transmission
• power transmission faults
• HVDC power convertors
• voltage-source convertors
• power transmission protection
• short-circuit currents
• fault currents
• DC fault protection
• multiterminal voltage source converter
• high-voltage direct current
• VSC–MTDC
• DC short-circuit fault ride-through
• full-bridge modular multilevel converter based MTDC systems
• FB-MMC topology
• fault current clearing
• full-bridge sub-module
• FB-SM
• converter protection control strategy
• system protection scheme
• quick fault current elimination
• protection strategy
• full-bridge MMC-based MTDC systems
• high-voltage direct current transmission systems
• DC short-circuit fault ride-through method
• simulation model