A New isolated DC-DC converter based-on MMC for high voltage applications

Abstract

Background/Objectives: In recent years, the demand for power converters in high voltage applications such as wind power, electric locomotive, BESS, HVDC has been increasing rapidly. However, there is a big challenge in high voltage application is from the limited ability of power electronics. Hundreds of studies have been conducting in order to figure out solutions which are able to increase working voltage of new semiconductor power switching devices. Methods/Statistical analysis: This paper proposes an effective circuit configuration of isolated DC-DC converter for medium voltage applications. Since the operating voltage range of the switching devices is limited, few researches of DC-DC configuration operating at high voltage are conducted. This is the main motivation for us to research the configuration of DC-DC converter operating at high voltage. The proposed configuration in this paper is divided two parts, the high voltage side is made up of serial modular multilevel converter (MMC), the other one is low voltage which is rectifier diode bridge, and both are linked by a high frequency transformer. Findings: A new configuration of DC-DC converter for high voltage applications is mentioned in this research. It is divided into two parts, the high voltage part is the MMCs while the low one is the H-bridge rectifier, and the high frequency transformer links these two parts. The output of the proposed converter independent on both ratio of transformer and switching algorithm. The configuration of the circuit, along with pulse-width-modulation (PWM) will be presented and verified by simulation and experimental results that can possibly prove practicality of the new topology. Improvements/Applications: The suggested converter is suitable for high voltage application with a high step ratio and isolation characteristics between source and load. A PWM based-on phase-shifted algorithm is presented to control the output voltage. Cell-rotated selection is applied to achieve a self-balanced capacitor voltage levels.