Non-Isolated DC–DC Converters for PV Applications: Review

Abstract

Non-isolated DC–DC converters are widely used in photovoltaic (PV), electric-vehicle (EV), microgrid (MG), and portable applications where galvanic isolation is unnecessary. Quadratic topologies, including quadratic Ćuk, SEPIC, Zeta, and hybrid converters, can provide wider conversion-ratio ranges and lower control complexity than cascaded multistage converters. This paper reviews classical Buck, Boost, Buck–Boost, Ćuk, SEPIC, and Zeta converters and their quadratic variants in terms of voltage gain, efficiency, and component stress. Hybrid structures, such as Ćuk/SEPIC, Zeta/Boost, and SEPIC/Buck–Boost converters, are also considered because of their high voltage gain or voltage-inversion capability. The principal challenges include nonlinear voltage gain, high switch-voltage and current stresses, and reduced efficiency, particularly under the wide input-voltage range required for maximum power point tracking (MPPT) in PV systems. Further areas where research is needed are insufficient implementation in real-time, inadequate thermal and electromagnetic interference analysis, and underdeveloped machine-learning based optimization.