A fundamental frequency modulation for module multilevel DC/DC converters

A fundamental frequency modulation strategy was proposed for the modular multilevel DC/DC(M2DC) converter aiming to reduce switching loss of sub-modules and calculation quantity of digital control system. The basic requirements and implementation method of the fundamental frequency modulation strategy were analyzed and a dual-sorting capacitor voltage-balancing strategy that ensures power balance of each sub-module capacitor was proposed. The effect of the fundamental frequency modulation on the design of sub-module capacitor parameter as well as the compatibility of the control system were also analyzed. In order to verify the validity of the fundamental frequency modulation and dual-sorting capacitor voltage-balancing strategy, a simulation model in Matlab/Simulink and a low power prototype were built. The results show that this modulation strategy not only possesses a good compatibility with the control system, but also has a capability to reduce the power loss of switching devices and the stress of the digital control system.