Digitally Controlled Energy Harvesting Power Management System

Abstract

Intermittent energy harvesting devices often have difficulties in harvesting the peak energy generated due to battery power limitations, which increase the size and cost of the device. This paper discusses a power electronics module (PEM) that is used to extract power from a human energy harvesting device according to the user's desired difficulty level while maximizing energy transfer into a battery. The PEM can temporarily store the peak power produced by the generator, allowing a reduction in the battery size required to regulate the average power produced by the harvester. A two-stage prototype (a digitally controlled average current mode boost converter and an average current mode buck converter) has been designed, and the experimental waveforms were captured to validate the control theories used in the PEM. The peak efficiencies of the boost and buck are measured to be 93% and 93.7%, respectively. The total PEM system efficiency is measured at 87.9% at an average input power level of 10 W. The PEM design was able to extract 50% more power than the single-stage converter without energy storage capability. The PEM is also used to demonstrate the flexible resistance control scheme capabilities of the device for broader usage in bioenergy harvesting research.