HVDC-based modular multilevel converter in the STATCOM operation mode

Abstract

In a futuristic vision, deeply interconnected ac and dc networks are expected, which would be restructured over the time in order to maximize the power transmission efficiency. In some grid configurations, grid-tied inverters can eventually become islanded from the dc grid by means of breakers and enhancing those converters with the static synchronous compensator (STATCOM) functionality can increase their value. In this context, there is an extra degree of freedom, which is the voltage drop that should be targeted between the dc poles of the converter. Due to the modular multilevel converter (MMC) flexibility, the converter energy storage and the average voltage generated in the converter arms can be managed to achieve some goals as the converter efficiency and ac power quality increase, conjointly with the voltage ripple reduction on the capacitor values. This work analyzes the referred degrees of freedom of the converter control and the correspondent impact on the converter operating performance.