Two-switch voltage equalizer using series-resonant inverter and voltage multiplier for partially-shaded series-connected photovoltaic modules

Differential power processing (DPP) converters and voltage equalizers have been proposed for series-connected photovoltaic (PV) modules to prevent negative influences of partial shading, such as significant reduction in power generation and the occurrence of multiple maximum power points (MPPs). However, since conventional topologies are based on multiple individual dc-dc converters, the number of switches required increases proportionally to the number of modules connected in series, increasing the complexity. A two-switch voltage equalizer using a series-resonant inverter and voltage multiplier is proposed in this paper. The circuitry can be dramatically simplified compared with conventional topologies thanks to the two-switch configuration. Although individual MPP tracking for each PV module is unfeasible, a shaded module would be operated at “near” MPP by properly exploiting the output resistance of the proposed equalizer. Experimental equalization tests using the prototype were performed for four PV modules connected in series emulating partially-shaded conditions. With the proposed voltage equalizer, the maximum powers increased compared to those without equalization, demonstrating the performance of the proposed voltage equalizer.