Reactor Sizing Criterion for the Continuous Operation of Meshed HB-MMC-Based MTDC System Under DC Faults

Half-bridge modular multilevel converter (HB-MMC)-based multiterminal HVdc (MTdc) technology is increasingly being adopted as a promising option in the power transmission and distribution fields. However, how to realize the continuous operation of HB-MMC-based MTdc system under dc bipolar faults presents a considerable challenge. Making full use of the operation characteristics of hybrid dc circuit breakers, a reactor sizing criterion for continuous operation of the meshed HB-MMC-based MTdc system under dc faults is developed based on the dynamic behavior of the dc fault current of HB-MMC. It contributes to cut off the dc fault current before triggering MMC blocking, without influencing the continuous operation of the healthy MTdc system. Data analysis and simulation of a three-terminal-meshed HB-MMC-based dc system are conducted to validate the effectiveness of the proposed reactor sizing criterion.