Model and Control of the Isolated Multi-Modular Converter

Multi-modular converters have proven to be one of the most suitable topology to be used in high and power applications. The modularity of these configurations offer several advantages, such as: high quality voltage, redundancy and high efficiency. In these converters, the series connection of modules increase the number of voltage levels, but also the floating voltage of modules with respect the neutral point connection which may give rise to isolation issues at the DC side. Because of this, modules with two or more conversion stages are used to provide isolation and to prevent high floating voltages. However, increasing the number of conversion stages, increase also the losses and the implementation costs. In order to overcome these drawbacks, a new configuration of multi-modular converter is proposed in this paper. The proposed converter provides isolation with one conversion stage by means of using low frequency transformers in each module. The main principle behind this concept, the control structure and simulation results are presented to validate the proposed configuration.