Current sensorless single-switch voltage equalizer using multi-stacked buck-boost converters for photovoltaic modules under partial shading

Differential power processing converters or voltage equalizers have been proposed and used for photovoltaic (PV) string comprising multiple modules/substrings connected in series in order to preclude negative influences of partial shading. The single-switch voltage equalizer using multi-stacked 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. An equalization strategy using the ΔV-controlled equalization is explained and discussed on the basis of comparison with other 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.