| Abstract [eng] |
The aim of this master’s thesis is to investigate load impedance matching methods for piezoelectric energy harvesters and, using modeling in COMSOL and LTspice environments, to identify the most efficient energy harvesting interface solutions. The work is motivated by the increasing demand for autonomous electronic systems and Internet of Things (IoT) devices, which require low‑power, self‑sustaining energy sources that reduce battery discharge and maintenance efforts. In the first part of the thesis, a literature review is presented: the fundamentals of the piezoelectric effect, the main piezoelectric materials for energy harvesters (PZT, PVDF) and their properties are discussed; typical structures and application areas of piezoelectric energy harvesters are analyzed; special attention is given to the importance of load impedance matching and to the main techniques, including passive (RC, LC), active (DC–DC converters), synchronized switching (SSHI, SECE) and adaptive MPPT‑based methods. The second part focuses on modeling a bimorph piezoelectric cantilever in the COMSOL Multiphysics environment. The influence of vibration amplitude, load resistance, beam length, piezoelectric layer thickness, excitation acceleration (G force) and tip mass on generated voltage, output power and resonant frequency is investigated. Based on the simulation results, the electrical parameters of the harvester and the ranges of optimal operating area are determined for further electrical interface design. In the third part, an equivalent Norton model of the piezoelectric generator is implemented in the LTspice environment, and several energy harvesting interfaces are analyzed: a passive diode bridge rectifier, an active MOSFET‑based AC–DC converter and synchronized charge extraction techniques (SECE, SSHI). Their performance is evaluated in terms of output power, energy transfer characteristics and sensitivity to load variations, and a comparative analysis of different topologies is carried out, showing under which conditions synchronized switching methods can achieve higher harvested power than passive rectifier solutions. |
