MVDC Network Balancing for Increased Penetration of Low Carbon Technologies

This paper outlines the case for using Medium Voltage Direct Current (MVDC) (5-50 kV) elements in distribution systems as a means to accelerate the deployment of low carbon technologies. The approach uses existing cable and overhead assets, originally designed into the ac system for security purposes. By selective conversion to dc, an inter GSP (grid supply point) balancing network can be created with modifications only required at substations. This approach allows for increased network transfer capability without increasing fault level as would be the case with conventional interconnection. Using data from a real-world Scottish suburban distribution network, the benefits and barriers to such an approach are examined. Power flows for the existing network are benchmarked under various present day and future loading scenarios. Controllable MVDC links are introduced to the network and power flow studies used to assess the value of such an approach to network reinforcement. Cost estimates for such a scheme are projected using data from industrial trials.