A High-Efficiency Hybrid Buck-Boost Photovoltaic Energy Harvester with Adaptive Fractional Open-Circuit Voltage Maximum-Power-Point-Tracking Control

Abstract

This paper presents an energy-efficient photovoltaic energy harvesting system achieving an ultra-wide input power (PIN) range by optimizing both maximum-power-point-tracking efficiency (ηMPPT) and power-conversion efficiency (ηCONV). An MPPT based on an adaptive fractional open-circuit voltage method is proposed to tune the fraction k based on PIN with only little power overhead, unlike other complex and power-hungry hybrid MPPTs. Also, the harvester maintains high ηCONV at low PIN levels thanks to its modified hybrid topology that operates as a buck-boost converter with three different control techniques. The proposed zero-current detection circuit reduces the control bit size and response time because it actively changes the tuning resolution according to PIN. The proposed system achieves ηMPPT >98% across a 10,000× PIN dynamic range, and the achieved ηCONV is greater than 81% across the whole range with a peak efficiency of 96.5%. Compared to other previous state-of-the-art works, this design provides the highest peak ηCONV as well as the widest PIN ranges, over which it achieves >98% ηMPPT and >80% ηCONV.