On the Stability of a Hardware Compensation Mechanism for Embedded Energy Harvesting Emulators

The possibility of emulating renewable energy sources by means of portable, low-cost embedded devices is a key factor for the design and validation of ultra low-power networked embedded systems. Full characterisation of hardware-software platforms used for reliably and adaptively generating energy traces is therefore needed in order to clearly understand their adoption for testing energy harvesting devices or protocols. We investigate in this study a recently proposed embedded ultra-low power solution, which targets energy harvesting sources emulation with real-time responsiveness. The analyzed platform has been previously evaluated in terms of accuracy and reactiveness. However, given the presence of a positive feedback mechanism implemented by means of a compensation circuit, the possibility of unstable dynamics could hinder its applicability. It is therefore deemed interesting to delineate the conditions which guarantee the stability of the system. The aim of this article is to investigate the problem, to formally derive the electrical loads to be powered that allow for operate in a stable regime, and to experimentally assess properties in realistic scenarios. Theoretical and experimental results highlight the flexibility of the analyzed platform in terms of its capability to quickly adapt to changes in load conditions, while retaining bounded output dynamics.