Modular Two-Switch Flyback Converter and Analysis of Voltage-Balancing Mechanism for Input-Series and Output-Series Connection

The voltage-balance mechanism is a required ability to simplify the control scheme for modular input-series and output-series (<inline-formula><tex-math notation="LaTeX">$\text{ISOS}$</tex-math></inline-formula>) connection, in spite of the fairly large number of studies, such mechanism has not been addressed clearly and satisfactory. This paper proposes a methodology, based on the converter output characteristics, to standardize the analysis of voltage-balance mechanism in steady state, which allows understanding the behavior of voltage sharing among the modules in steady state, in the presence of mismatched parameters for <inline-formula><tex-math notation="LaTeX">$\text{ISOS}$</tex-math></inline-formula> connection of modular converters. In addition, the <inline-formula><tex-math notation="LaTeX">$\text{ISOS}$</tex-math></inline-formula> connected modular two-switch flyback converter is presented. The intrinsic voltage-balance mechanism, even operating in continuous conduction mode, make this converter feasible, as an alternative to the predecessors modular converters. The operation and analysis of the proposed connection were corroborated, based on the experiment carried out on a laboratory prototype with three modules: <inline-formula><tex-math notation="LaTeX">${\text{1}}, {\text{200 V}}_{\text{dc}}$</tex-math></inline-formula> total input voltage, <inline-formula><tex-math notation="LaTeX">${\text{1.5 kW}}$</tex-math></inline-formula> rated power, and <inline-formula><tex-math notation="LaTeX">$\text{50 kHz}$</tex-math></inline-formula> switching frequency. This paper is accompanied by a video demonstrating the operation, in steady state, of the laboratory prototype.