Steady-State Analysis of the Modular Multilevel Converter

In this paper, the steady-state behavior of the modular multilevel converter (MMC) is studied under balanced and unbalanced AC grid voltage conditions. The suggested mathematical model is derived combining the converter internal arm variables and both AC and DC grids variables. Moreover, the steady-state solution of the system can be achieved by setting the internal power balance within the converter. In order to verify the steady-state model, different types of AC fault conditions are imposed, and the output values are compared with the simulation results of an average model of the MMC circuit. The results show that the proposed analysis is in close agreement with the simulations for all conditions evaluated, validating the developed equations.