Control and Protection Scheme of VSC HVDC Transmission System having the Ability to Control DC Fault Current

Abstract

Practical application of the VSC (Voltage Source Converter) HVDC system is progressing recently due to its superior control performance over the conventional line-commutated converter type HVDC system. Introduction of the VSC HVDC will continue to spread further by the appearance of MMC (Modular Multilevel Converter) topology.
At present, AC circuit breaker is tripped to clear fault when a DC fault occurs at a VSC HVDC system. Tripping AC circuit breaker delays recovery from the fault. The application of the full bridge cell MMC is considered as one of the solutions to clear the fault without tripping AC circuit breaker. However, any specific control scheme using the full bridge cell MMC has not been proposed. We propose a novel control scheme of the VSC HVDC system which can control DC fault current and recovery quickly from the fault.
We verified performance of the control scheme through transient simulation. The VSC HVDC system can maintain stable operation without overcurrent and overvoltage on semiconductor devices during entire AC and DC fault period. It was confirmed that HVDC system with the control scheme can restore power transmission quickly after both AC and DC system faults.