Overall control scheme for VSC-based medium-voltage DC power distribution networks

With the development of power electronics technology, numerous studies have been conducted on voltage-source converter-based high-voltage DC (VSC-HVDC) transmission technology and low-voltage DC micro-grids. However, DC power distribution networks are more sophisticated than HVDC transmission networks with respect to the complex topology, changeable operation modes and use of diverse power electronic devices. Research on voltage-source converter-based medium-voltage DC (VSC-MVDC) distribution networks is still in its infancy stage, and whether or not some of the existing control and protection schemes used in VSC-HVDC can be applicable to the distribution networks remains a question. In this study, a dynamic simulation platform with DC circuit breakers is initially established. This platform is based on the first dual-terminal VSC-MVDC distribution network constructed in China. Second, a complete overall control scheme is proposed for VSC-MVDC distribution networks. The control scheme is proposed with an array of control strategies, including controls for system startup/shutdown, voltage coordination, operation mode transition, single-station integration, system fault isolation, and recovery. Finally, the proposed scheme is validated through experiments using the dynamic simulation platform. Experimental results indicate the effectiveness of the proposed overall control scheme for VSC-MVDC power distribution networks. Thus, the proposed scheme can be used in the design and operation of future VSC-MVDC distribution networks.