An H-Bridge Modular DC-DC Converter with Bidirectional Flyback-Based Energy Equalization Modules

Conventional Modular Multilevel Converter (MMC) is a promising candidate in high-voltage high-power applications. Unfortunately, operating the conventional MMC with DC output voltage results in unbalanced capacitors' voltages. In literature, Dual Half Bridge (DHB)-based Energy Equalization Modules (EEMs) concept was presented; where EEMs can be employed with phase shift control to transfer energy between the upper and lower submodules (SMs) in the same leg to keep balanced capacitors voltages with low ripples during the DC/low frequency operation of the conventional MMC. In this paper, an H-bridge Modular DC-DC converter with flyback-based EEMs is presented. The bidirectional flyback-based EEMs provide the needed energy equalization task simply by operating the flyback converter with 50% duty cycle; which is simpler when compared with the DHB-based EEMs. Detailed illustration of the proposed architecture is presented. Simulation results are presented to show the effectiveness of the bidirectional flyback-based EEMs.