1 Continued Operation of Multi-Terminal HVDC Networks Based on Modular Multilevel Converters

A comprehensive study that explores the possibility of using passive networks and active converter control to facilitate continued operation of multi-terminal HVDC networks with minimum interruption during pole-to-pole dc short-circuit faults is presented. The primary objective of this study is to achieve continued operation of any multi-terminal HVDC network using relatively slow dc circuit breakers (with minimum operation time of 10ms), without over-stressing converter switches and without converter dc link voltages falling below the peak ac line voltage. The validity of the proposed method is confirmed using time-domain simulations. Results obtained from iterative simulations confirm the possibility of further extension of fault clearance time to more than 10ms, but at the expense of increased passive component size