Validation of a Reduced Order Model for Modular Multilevel Converters and Analysis of Circulating Current

In this paper, a recently proposed reduced order model for Modular Multilevel Converters is validated and used to analyze the role of the circulating current in the power transfer inside the converter. This model simplifies the analysis of the converter by removing the discontinuities and reducing the order of the system. Therefore, continuous analytical expressions can be obtained and analyzed. The reduced order is used to model the dynamics of the state space variables of the converter. The results show that, the higher the number of modules used in the converter, the more accurate are the results of the model. Moreover, the influence of different harmonic components of the circulating current over the module's voltage ripple, and the influence of the circulating current components on the power transfer in the converter are analyzed. Inter alia, the analysis shows the importance of the even order harmonics of the circulating current in the reactive power transfer within the converter.