A Novel Hybrid Multilevel DC–DC Converter Employing Trapezoidal Modulation

This article presents a new hybrid multilevel converter for medium voltage dc–dc interconnection. The structure of the topology is a hybrid of two-level converter and the modular multilevel converter (MMC). The proposed converter provides three-phase trapezoidal output voltages with a controlled slope while using only a single MMC leg. Therefore, using fewer submodules and sensors, and with its feature of low energy storage requirement (ESR), the overall size of the converter reduces. The front-to-front configuration of the proposed converter provides the desired voltage matching, grounding flexibility, and dc fault blocking capability. Moreover, the phase leg switches and the bidirectional switches of the converter are operated in the soft switching mode reducing the converter losses. A detailed mathematical analysis is presented to substantiate the low ESR and losses of the proposed converter. The performance evaluation of the proposed dc–dc converter is carried out in PSCAD/EMTDC and analyzed in detail. The operation of the converter is also verified on a developed scaled-down laboratory prototype.