Adaptive Capacitance Circuit for Optimal Dynamic Impedance Matching in Variable Reluctance Energy Harvesting Applications

Energy Harvesting (EH) is considered one of the topics that will enable the mass deployment of autonomous Internet of Things (IoT) devices. This paper is focused on Variable Reluctance Energy Harvesters (VREH) which gather energy from the rotation. As these systems feature an inductive output impedance and generate a sinusoidal voltage with variable frequency, it is necessary to perform capacitive impedance matching to maximize power transfer for each working frequency. In this paper, an adaptive capacitance circuit optimization methodology is designed and implemented for a VREH application with the aid of genetic algorithms (GA). This enables to determine in the design phase, for different number of capacitors in parallel, their value and which combinations to use at each frequency to reach the power closest to the maximum possible one. The system is tested in an experimental setup, obtaining output power levels close to the ideal ones over a wide range of frequencies.