Reactive power loading of components within a modular multi-level HVDC VSC converter

The modular multi-level (MMC) HVDC VSC converter topology is becoming widely accepted as the de facto standard topology. Whilst it is normal to consider primarily the real power capability of such a converter it is worth bearing in mind that the origins of the circuit application to AC power systems was in STATCOM applications. This paper will look at the basic main circuit components of a modular multi-level converter and show how the real and reactive capabilities of these components are not symmetrical. These capabilities potentially offer additional rating, even on a temporary basis from the equipment. The paper will further look at the power electronic converter and compare two different types of multi-module converter, showing how the topology affects the reactive power capability of the converter.