A Unidirectional Modular Magnetic-Coupled Converter (MMCC) With Reduced Switch Capacity for None-Regenerative Motor Drive

Although the conventional modular magnetic-coupled converter (MMCC)-based motor drive significantly improves power density, it suffers from high switch capacity. To address this issue, this article proposes a diode-based unidirectional MMCC, which reduces the capacity of fully-controlled switches by 39.5% compared with the conventional MMCC. Replacing switches with diodes complicates the DC capacitor voltage balancing principle and poses challenges to capacitance design. To solve these issues, the voltage balancing principle is revealed via the unique alternating conduction circuit model, without complex control strategies. Based on this principle, a dedicated DC capacitance design method is proposed, enabling the DC capacitance to be minimized even under zero/low-speed rated-torque operation. Moreover, system efficiency is improved by 0.3% due to the incorporated diodes. The feasibility of the proposed topology is verified via 4160-V 1-MVA simulations and 380-V 8-kVA experiments.