Energy Harvesting Power Converter for Variable Impedance and Voltage Sources

This article describes a converter, along with a novel control algorithm, for harvesting energy from unconventional energy sources, such as stray currents from electrified railroad lines. Such energy sources are often characterized by high resistance and have variable open-circuit voltage and source resistance. The converter was, and the model was tested in detail using both simulations in LTSpice and in practice, using a prototype. A high correspondence of the presented model with simulations and actual measurements was observed. The device and algorithm operate in maximum power transfer mode and allow up to 90% of the available energy to be recovered and stored in a battery, which is an integral part of the converter. To the best of the authors’ knowledge, this is the first such converter described. Since all design recommendations and all the dependencies needed to calculate the control parameters are provided, the presented control algorithm can be easily implemented in a converter meeting the general requirements of a buck–boost converter.