A Novel Hardware and PWM Scheme for Modular Multilevel Converter using Wide Band Gap Devices

This paper presents a new modulation scheme for a low loss, low cost, modular multi-level converter to connect renewables to the grid at medium or high voltage. The proposed scheme generates a multi-level voltage output with low loss, low harmonic distortion, and is modular in nature. Modular Multilevel Converters (MMC) with high frequency transformers are becoming popular due to high efficiency, lower harmonics and less size compared to conventional transformer. The topology discussed in this paper compromises of a full-bridge converter, which is then connected to multiple High Frequency Link sub-modules via high frequency transformers. Each sub-module produces its own isolated DC voltage, and modules are inserted or removed to synthesize high AC voltages. In this paper, the switching loss and cost is analyzed for different modulation techniques and is compared with the proposed scheme which includes wide band devices. Various PWM schemes are analyzed using MATLAB/Simulink and the simulation results are presented in this paper.