Single-Switch Voltage Equalizer Using Multistacked Buck–Boost Converters for Partially Shaded Photovoltaic Modules

Partial shading on a photovoltaic (PV) string comprising multiple modules/substrings triggers issues such as a significant reduction in power generation and the occurrence of multiple maximum power points (MPPs), including a global and local MPPs, that encumber MPP tracking algorithms. Single-switch voltage equalizers using multistacked buck-boost converters are proposed to settle the partial shading issues. The single-switch topology can considerably simplify the circuitry compared with conventional equalizers requiring multiple switches in proportion to the number of PV modules/substrings. The proposed voltage equalizers can be derived by stacking capacitor-inductor-diode filters on traditional buck-boost converters, such as SEPIC, Zeta, and Ćuk converters. The optimum equalization strategy is also proposed and discussed for the equalizers to compensate the partially shaded PV modules efficiently. Operational analysis based on a simplified equivalent circuit is performed for a SEPIC-based topology. Experimental equalization tests using the SEPIC-based voltage equalizer were performed emulating partially shaded conditions for a PV panel comprising of three substrings. Local MPPs were eliminated and extractable maximum powers increased by the equalizer, demonstrating the efficacy of the proposed voltage equalizer.