On Systematic DC Fault-Ride-Through of Multi-terminal MMC-HVDC Grids

Development of Modular Multilevel Converter (MMC) based HVDC grids, as a new generation of Voltage Source Converter (VSC)-HVDC systems, has been considerable through the past decade. Emerging of multi-terminal MMC-HVDC networks makes integration of multiple large-scale sustainable sources and asynchronous power grids quite feasible. However, protection and control of the multi-terminal HVDC grids under fault situations have always been a vital issue. On the other hand, while modern AC grids get benefits of applied Fault-Ride-Through (FRT) operation and capabilities under AC fault conditions, the multi-terminal HVDC grids lack a systematic DC FRT operation. As the multi-terminal HVDC networks are going to become a backbone grid for the future power systems, it is necessary to define grid code requirements and standardizations considering DC FRT regulations. This paper presents potential DC FRT operations and possible profiles from HVDC grid point of view under DC fault conditions. A systematic DC FRT based on voltage against time profile is proposed. Different characteristics of voltage-based DC FRT are investigated in this study and results can be applicable to DC grid code definitions and requirements.