Optimal operation mode for Modular Multilevel Converter based HVDC

In this paper an analytical study on the Modular Multilevel Converter architecture applied to HVDC is presented. The influence of the circulating injected currents on the converter performance is the main object of this analysis. In particular, the influence of the second and fourth harmonics circulating injected current on the capacitor voltage ripple in a general working point are object of investigation. The main four working points, inverter, rectifier, inductive and capacitive, are studied in detail.