Dual MPPT Control and Field Testing for Switched Capacitor-Based Cell-Level Power Balancing Utilizing Diffusion Capacitance of Photovoltaic Cells

Capacitorless switched capacitor converter (SCC)-based voltage equalizers utilizing diffusion capacitance of photovoltaic (PV) cells have been proposed to increase the energy yield from partially-shaded PV modules. Although this equalizer offers simple and miniaturized circuit thanks to the capacitorless topology, the performance optimization is an elusive task as the optimal duty cycle to achieve the lowest power conversion loss is dependent on shading conditions and module configurations. This paper proposes a dual MPPT algorithm that controls duty cycles of not only the capacitorless equalizer but also a front-end boost converter. With the dual MPPT control, in addition to the operation at an MPP, the proposed equalizer can operate at an optimal duty cycle, at which the total Joule loss in the equalizer is minimized. A prototype of the proposed equalizer for six-cell module was built. The experimental results demonstrated the efficacy of the proposed equalizer as well as the dual MPPT.