Load- and Position-Independent Moving MHz WPT System Based on GaN-Distributed Current Sources

This paper describes the modelling, analysis, and design of a complete (dc-to-dc) inductive wireless power transfer (WPT) system for industrial moving applications. The system operates at 6.78 MHz and delivers up to 150 W to a load moving along a linear path, providing a quasi-constant dc output voltage and maintaining a zero voltage switching operation, regardless of position and load, without any retuning or feedback.

The inductive link consists of an array of stationary transmitting coils and a moving receiving coil whose length is optimized to achieve a constant coupling coefficient along the path. Each Tx coil is individually driven by a constant amplitude and phase sinusoidal current that is generated from a GaN-based coupled load-independent Class EF inverter. Two adjacent transmitters are activated at a given time depending on the receiver’s position; this effectively creates a virtual series connection between the two transmitting coils. The Rx coil is connected to a passive Class E rectifier that is designed to maintain a constant dc output voltage independent of its load and position.

Extensive experimental results are presented to show the performance over different loading conditions and positions. A peak dc-to-dc efficiency of 80% is achieved at 100 W of dc output power and a dc output voltage variation of less than 5% is measured over a load range from 30 to 500 Ω.

The work in this paper is foreseen as a design solution for a high-efficient, maintenance-free, and reliable WPT system for powering sliders and mass movers in industrial automation plants.

This paper is published with Open Access on IEEE Xplore:

A. Pacini, A. Costanzo, S. Aldhaher and P. D. Mitcheson, “Load- and Position-Independent Moving MHz WPT System Based on GaN-Distributed Current Sources,” in IEEE Transactions on Microwave Theory and Techniques, vol. PP, no. 99, pp. 1-10. doi: 10.1109/TMTT.2017.2768031

PhD Tutorial: Position and Load Independent DC to DC Wireless Power Transfer System for Moving Applications

In order to pass to the third year of the PhD at the University of Bologna, it is required to give a 40 minutes presentation to first introduce your field, in the form of a tutorial, and then briefly show your research.

The presentation is organized as follows

• Tutorial
  • Introduction to Wireless Power Transfer (WPT)
  • Inductive Power Transfer (IPT)
  • Class E Resonant Inverter
  • Advantages of Wide Bandgap Semiconductors (WBG)
• Research Contribution
  • Geometry Optimization of Sliding Inductive Links for Position-Independent Wireless Power Transfer
  • Design of a Position-Independent End-to-End Inductive WPT Link for Industrial Dynamic Systems

Introduction to Wide BandGap Semiconductors and Class E rectifier

As an assignment to achieve the PhD credits for the Summer School of Information Engineering, it was requested to write a short report. This is a very simple introduction to Wide BandGap Semiconductors and Class E rectifier.

Python matplotlib: insets and aligned legends

Sometimes it is needed to create a plot with several lines and to assign a legend to each of them, which quite often ends in cumbersome and clunky legends. In my opinion, a more elegant way is include the legend as aligned text aside to each plot line, which is possible using Python and matplotlib.

Furthermore, to better highlight some details it is also possible to use an inset, hence to add a box which zooms a particular detail of the plot.

In the following is the Python code. The style is optimised for an IEEEtran journal.

Peer review template based on IEEEtran and pandoc

When you start to be involved in scientific publishing, one of the side-effects is to become a reviewer for some journals. This side-effect is an extremely important part of the scientific publishing process, which should ensure the quality of the published papers. It has also some other advantages, as to be able to view the papers few months before they would be published. The major downside is the time required for a good review, even days.

To simplify the writing process I decided to create a simple workflow which is based on \(\LaTeX\), IEEEtran and pandoc. The final output will be made up of a .pdf file, formatted as an IEEEtran journal, and a .rst file, formatted as a reStructuredText. The .pdf is ideal for viewing the math, figures, etc., while the .rst file is ideal to be pasted in the comments part, which is the part that will be sent in the email to the authors.

International Morse Code

This is a nerdy post, just to share a cheat-sheet which contains the International Morse Code along with the NATO Phonetic alphabet. I created this, using various resources online, just to lose some time…

Import a RF design (and logos) from svg, png or Gerber files into Kicad

KiCad is a wonderful software for PCB designing, it is open-source and can handle the complete workflow from the schematic to the final layout.

Unfortunately, it is not (yet) intended for RF circuit and antenna design. In these cases, a suitable program should be used, which could be ADS, CST, HFSS, or others. These are expensive but, unfortunately, the open-source tools are still not complete enough. I generally use multiple open-source tools depending of the requirements and quite often compare the results to evaluate the correctness.

Long story short, I was facing with the need to create a PCB by incorporating some custom Inductive Power Transfer coils, which I could export to a Gerber file from CST and some patch antennas and matching circuits, from ADS. The idea was to import the different parts from the Gerbers into different footprints, which are then assigned to schematics blocks and placed on the PCB.

There are no ways (yet) to get it simply by using some pre-baked functions, but some tricks are needed.

This post is a walk-through different options that can be used. I try to compare the options and outline the strengths of each one.

Notice that the same methods can be used to produce custom logos or any custom shape.