Transient capability assessments of HVDC voltage source converters

This paper assesses the transient capabilities of HVDC transmission systems based on two-level, neutral-point clamped, two-switch modular, and H-bridge modular multilevel voltage source converters. This investigation aims to identify voltage source converter topologies that may operate safely in steady-state and survive ac and dc network disturbances, with minimum impact on overall system stability. In this assessment, detailed switching models of the aforementioned converters are used to model HVDC converter stations, with all associated controllers incorporated (active power, current and ac voltage controllers, and cells capacitor voltage balancing). A detailed comparison that highlights the major performance differences between these converters is presented.