Ripple Decoupling of Modular Multilevel Converter with Flux Cancelled Three-port Converter

This paper proposes a new MMC topology with three-port converter that using customized LLC circuits to couple the SMs from same voltage level together. The fundamental and the 2nd order harmonic current ripple can be eliminated as their induced magnetic flux are cancelled in the coupled core. Thus, system power density and efficiency can be significantly improved since the capacitor size is much reduced. In addition, planar transformer design is applied due to its excellent low-profile characteristic and the related down-scale SM prototype is demonstrated. The Detailed simulation results of comparison between proposed topology and traditional MMC have been presented. Moreover, motor drive starting from zero frequency is also simulated. The SM preliminary experiments are also demonstrated and analyzed.