Optimization of Electrical Interface for Vibration-based Energy Harvesters for Low Power Applications

• Author / Creator

  Badr, Ahmed Osman Abdel-Latif Ahmed

• Piezoelectric Energy Harvesters (PEHs) can be used to supply power to small
  electronic devices as the Wireless Sensor Nodes (WSNs). However, the harvested
  energy from the harvesters are usually little and needs to be stored into storage
  elements. A high-efficiency electrical interface with minimum power losses is
  required to bridge between the PEHs and the storage device.
  In this thesis, a novel self-powered high-efficiency Negative Voltage Converter –
  Parallel Synchronized Switch Harvesting on Inductor (NVC-PSSHI) AC/DC
  interface circuit is designed to rectify the output AC voltage from the PEH to DC
  voltage. The NVC-PSSHI interface, built with discrete components, targets low
  voltage (2 Vpp to 7 Vpp) and low power applications (in the microwatt power
  range). Analytical, simulation and experimental work with a single PEH have
  been provided to prove and validate the NVC-PSSHI interface circuit.
  The output power from a single PEH might not be enough to power the electrical
  interface. Therefore, analyzing the output power from an array of PEHs against
  several operating conditions is of great importance, to determine the conditions of
  maximum output power from the PEH array. An analytical model is derived to
  calculate the output power from an array of PEH against the voltage magnitude
  and phase angle mismatch between the PEHs in the array, the number and
  connections (series and parallel) of the PEHs in the array, and the loading
  resistance connected to the PEH array. Experimental work with 4 PEHs is
  provided to compare with the analytical results.iii
  In order to charge a Lithium-Polymer (LiPo) battery at 4.2 V, a battery
  management (BM) circuit is needed. The designed high efficiency NVC-PSSHI
  interface circuit is validated with a selected battery management (BM) circuit for
  low power applications. The two-stage NVC-PSSHI BM interface is powered by
  an optimized array of PEHs to maximize the overall efficiency from the energy
  harvesting system.
  The maximum efficiency of the novel self-powered high efficiency NVC-PSSHI
  interface reaches 82.1% when powered by a single PEH and loaded with 15 kΩ
  resistance. Compared to the conventional PSSHI interface, the designed NVCPSSHI improves the efficiency by up to 23.4% at 3 Vpp and 100 Hz frequency.
  Considering an array of 2 PEHs, a higher reduction of output power occurs when
  the voltage mismatch from the 2 PEHs is 1 Vpp (35%), while only 25% of the
  output power is reduced when the phase angle mismatch is ±60°. The
  experimental output power deviation of 2 PEHs from the analytical results reaches
  a maximum of 16.5% for the series connection and 19.5% for the parallel
  connection. The maximum efficiency of the NVC-PSSHI BM interface reaches
  77% at 100 kΩ loading resistance. The two-stage energy harvester interface can
  charge a 1 mF super capacitor to 4.2 V in around 7 minutes, and a LiPo battery
  from 3.8 V to 4.1 V in 14 days with charging current at 50 μA.

• Subjects / Keywords

  • Energy Management
  • Piezoelectric Energy Harvesters
  • AC/DC Converters
  • Low Power Applications

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-b06n-zr52

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.