High-Gain Modular Multilevel DC–DC Converter for Renewable Energy and HVDC Applications

Abstract

High-voltage direct-current (HVDC) transmission, offshore wind integration, and emerging hybrid AC/DC infrastructures demand high-gain DC–DC converters that combine scalability with reduced implementation complexity. This article introduces a nonisolated modular multilevel DC–DC converter that achieves a substantial voltage step-up using a chain of identical submodules (SMs) arranged symmetrically to maintain uniform device stress and inherent power sharing. The structural symmetry naturally produces interleaved switching patterns, leading to reduced output ripple without requiring additional control overhead. A relative-voltage control approach with a zero reference further limits the number of sensing and feedback loops, enabling practical scalability to higher level configurations. Steady-state analysis is used to obtain expressions for voltage gain, inductor current ripple, and capacitor voltage ripple, clarifying the influence of design parameters. The architecture is well-suited for renewable-energy sources requiring medium and high-voltage DC interfacing. Experimental results from a laboratory prototype confirm accurate gain regulation, low output ripple, balanced submodule operation, and stable dynamic behavior, demonstrating the feasibility of the proposed architecture.