Coupling between the frequency droop and the voltage droop of an AC/DC converter in an MTDC system

Abstract : —MTDC systems are required to be reliable, and in certain cases, should participate in the AC grids frequency regulation. This can be achieved by providing AC/DC converters with a dual controller combining both the voltage-droop and the frequency-droop control techniques. In this paper, the coupling between the two droops is theoretically investigated and quantified for both a DC side fault and an AC side fault. A 5-terminal HVDC grid is simulated to validate the theoretical results.