The control and performance of a series connected multiterminal HVDC transmission system

The feasibility of a series connection of stations in a multiterminal HVDC transmission system is demonstrated. Techniques were developed to control this system, and the operation of the system was studied on a large power system simulator. The performance of the system was shown to be similar to conventional point to point systems with most control functions being carried out by local controls. An overall system control is shown to be necessary only for optimizing load distributions. Given adequate tap changer ranges on the converter transformers the increase in valve damping and system reactive power requirements are shown to be moderate. The series connected multitermimal system is shown to have a number of advantages over the alternative parallel connected system for certain applications.