DC/DC Converters Based on Hybrid MMC for HVDC Grid Interconnection

This paper presents a multi-terminal high-power DC/DC converter configuration based on hybrid MMC topology with fault blocking capability for interconnecting HVDC systems. Its main functions include bidirectional power flow, step-up and step-down operation and fault isolation equivalent to a DC circuit breaker. By contrast to the conventional MMC based DC/DC converter, the proposed DC/DC converter with hybrid MMC configuration has the advantage of being able to block the DC/DC converter terminal connecting to faulty DC grid section, while continue operating the other terminals connected to healthy DC grid sections. The proposed DC/DC converter operation is analyzed and its control is described. Simulation results using Matlab/Simulink are presented to demonstrate the robust performance during dc fault conditions.