A Continuous MPPT Technique Independent of Inversion Factor for Piezoelectric Energy Harvesting

The paper proposes a continuous maximum power point tracking (MPPT) technique for piezoelectric energy harvesting that is independent of the inversion factor. The MPPT solution is obtained using the proposed fractional differential voltage (FDV) method, which is implemented by sampling the peak voltage and inversion voltage of the working piezoelectric transducer (PZT) during continuous energy harvesting. Compared to existing solutions, the proposed method no longer disconnects the PZT from the interface circuit to achieve open circuit voltage sampling or pre-measures the interface circuit’s inversion factor. In addition, the interface is implemented by the self-powered rectifier-less synchronized switch harvesting on inductor (ReL-SSHI) circuit. The experiment results show that the proposed MPPT method can assist the ReL-SSHI circuit to maintain the maximum power output regardless of the changing types of interfaced PZTs and inductors, and a peak MPPT efficiency of 98% is obtained.