Sizing of branch inductors parameters in modular multilevel converters: An analytical approach

One of the key features of Modular Multilevel Converters is the existence of inductors inside the branches that constitute each of their phases. These inductors, which may be coupled or non-coupled, authorize a certain independency in the control of the branch currents and contribute to the protection of the converter as well as the buses the latter is connected to. Through the analysis of the various current loops that are involved in this converter technology, the present paper aims to present a general parameter design method and proposes several criteria in order to analytically size these branch inductors. The possible use of coupled inductors is considered and compared with the use of non-coupled inductors. Finally, a numerical example as well as simulation results illustrate and confirm the validity of the proposed approach.