Stablity of a modular multilevel converter based HVDC system considering DC side connection

摘要

This paper conducts a detailed analysis on the dc side interaction of a modular multilevel converter based HVDC system. The dc side is modelled as a cable system with a voltage controlled remote converter. To implement such research, detailed small-signal models of a point-to-point MMC-HVDC system with consideration of the internal harmonic dynamics are established, based on the concept of “dynamic phasors”. For this purpose the cable system is modelled as a T-section consisting of inductors and capacitors. The developed small signal model is also validated by comparing its results with a detailed Electromagnetic Transients Simulation of the ac-dc system. The dc interaction modes are identified with participation factors. The influence of the outer loop controller parameters, the internal circulating current suppressing controller, the dc line parameters on the interaction modes is analyzed.