Two-Dimensional PO MPPT Technique for Piezoelectric Vibration Energy Harvesters

This paper is focused on resonant Piezoelectric Vibration Energy Harvesters (PVEHs). In all energy harvesting applications, and in particular in PVEH applications, the maximization of the extracted power is mandatory. It is well known that, in order to maximize the harvested power, it is necessary to get the optimal matching between the harvesting device and the load. In particular, in PVEH applications under purely sinusoidal input vibrations, in order to maximize the harvested power, the impedance of the load must be coincident with a well-defined optimal impedance ZOPT. However, in practical applications, the load of PVEHs is not a linear impedance, but it is nearly always represented by a non-linear AC/DC converter. In this paper, the full-bridge based active AC/DC architecture, that is theoretically able to emulate just the optimal impedance ZOPT, is analyzed in detail. In particular, a Two-Dimensional Perturb and Observe (TD-P&O) algorithm is proposed and discussed for the emulation of such an optimal impedance. Simulation results confirming the validity of the proposed TD-P&O algorithm and the increase of the extracted power with respect to the simpler case of a diode bridge rectifier source/load electronic interface are presented and discussed.