A CMOS Energy Harvesting Interface Circuit With Cycle-to-Cycle Frequency-to-Amplitude Conversion MPPT for Centimeter-Scale Wind Turbine

• Published in: IEEE transactions on circuits and systems. I, Regular papers Regular papers, 2021-09, Vol.68 (9), p.3587-3597
• Main Authors: Zeng, Zizhen, Estrada-Lopez, Johan J., Wang, Bo, Sanchez-Sinencio, Edgar
• Format: Article
• Language: English
• Subjects: Amplitudes; cm-scale; CMOS; Converters; Efficiency; electromagnetic; Energy conversion efficiency; Energy harvesting; Field study; Frequency conversion; frequency-to-voltage converter; Loading; Maximum power point trackers; maximum power point tracking; Maximum power tracking; micro wind turbine; rectifier; Rectifiers; Turbines; Wind; Wind energy; Wind speed; Wind turbines; zero-current-switching
• ISSN: 1549-8328; 1558-0806
• DOI: 10.1109/TCSI.2021.3087790

An energy harvesting (EH) system is proposed to extract energy from a centimeter-scale electromagnetic (EM) micro wind turbine. To improve the end-to-end efficiency, an autonomous and self-biased active rectifier is employed. A hysteresis-controlled boost converter is designed with self-zero-current-switching calibrations, which achieves a peak DC-DC efficiency of 93.3% with a maximum efficiency improvement of 12.7%. In addition, a novel frequency-to-amplitude conversion (FAC) maximum power point tracking (MPPT) method is proposed for a cycle-to-cycle MPPT. In measurements, the proposed FAC MPPT requires no more than three cycles to locate the maximum power point (MPP) in abrupt frequency changes, with an 80% tracking accuracy in the first turbine cycle. In wind-field testing, the EH system starts to track the MPP one cycle after start-up at 2.0 V. In the steady-state, the EH system maintains its cycle-to-cycle MPP under different wind conditions. In wind-field testing for wind speeds from 1.0 to 5.0 m/s, the peak MPPT accuracy is 99.27%, with an MPPT efficiency of 99.85%. The extracted power is from 0.1 to 8 mW with a peak end-to-end efficiency of 88.2%. Compared to a full-bridge rectifier, a 630% energy extraction gain is measured at a low wind speed of 1.2 m/s. To the best of the authors' knowledge, this is the first IC prototype for a cm-scale EM wind turbine EH to achieve a cycle-to-cycle MPPT with the highest reported MPPT efficiency.