Current Sensorless Equalization Strategy for a Single-Switch Voltage Equalizer Using Multistacked Buck–Boost Converters for Photovoltaic Modules Under Partial Shading

Differential power processing converters and voltage equalizers have been proposed and used for photovoltaic strings comprising multiple modules/substrings connected in series in order to preclude negative influences of partial shading. The single-switch voltage equalizer using multistacked buck-boost converters can significantly reduce the necessary switch count compared to that of conventional topologies, achieving simplified circuitry. However, multiple current sensors are necessary for this single-switch equalizer to effectively perform equalization. In this paper, a current sensorless equalization technique (ΔV-controlled equalization) is presented. The equalization strategy using the ΔV-controlled equalization is explained and discussed on the basis of comparison with current-controlled equalization strategies. Experimental equalization tests emulating partial-shading conditions were performed using the single-switch equalizer employing the ΔV -controlled equalization. Negative impacts of partial shading were successfully precluded, demonstrating the efficacy of the proposed ΔV-controlled equalization strategy.