Current-fed Modular Multilevel Converter (CMMC) for Fuel Cell and Photovoltaic Integration

Modular multilevel converters (MMCs) have demonstrated superior performance as a power conditioning stage (PCS) in several applications within low-, medium-, and high-voltage areas. Meanwhile, it is still mandatory to embrace the boosting capability within the power conditioning stage in some of these applications, such as fuel cell and photovoltaic-fed systems, due to the unregulated low-voltage (LV) output of these DC sources. As a consequence, the utilized PCS will be based on a two-stage configuration, which is seen to be a bulky solution. Hence, this paper proposes a current-fed MMC (CMMC) topology as a single-stage solution for interfacing an LV DC source with a higher voltage AC load or grid. The proposed converter embraces the boosting capability within the inversion operation, while maintaining the merits of the traditional MMC. Such converter can be utilized in both LV and MV systems, where LV MOSFETs can be utilized in the LV ones in order to benefit from their low ON-state resistance and increase the power conversion efficiency. The proposed converter is analysed and simulation results using PLECS are included in this paper for a 10 kW three-phase CMMC in order to verify its functionality and the reported analysis.