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Multi-band Adaptive Impedance Compensation Methods for Spatially Robust Capacitive Power Transfer Systems
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  • Masoud Ahmadi ,
  • Hoda Dadashzadeh ,
  • Loïc Markley ,
  • Thomas Johnson
Masoud Ahmadi
University of British Columbia

Corresponding Author:[email protected]

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Hoda Dadashzadeh
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Loïc Markley
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Thomas Johnson
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Abstract

Our paper compares the merits of using both adaptive load resistance and adaptive frequency for impedance compensation of large spatial variations in capacitive power transfer (CPT) systems. We show through an equivalent circuit model how changes to load impedance or changes to frequency can be used to maintain a constant input impedance to the CPT link as the separation distance between the transmit and receive electrodes is varied. In previous works, frequency compensation required continuous adjustment to track spatial changes, thereby requiring broad operating bands for broad spatial ranges. Here, we combine discrete frequency compensation with continuous impedance compensation to keep transmission frequencies within specific narrowband ISM channels.
This work presents a practical implementation of spatially robust CPT systems. We consider the limitations of band-limited wireless power channels and apply frequency compensation as discrete frequency changes that are switched between different bands. In this way, frequency compensation offers coarse impedance control for large spatial changes. We then combine the band switching with load impedance compensation methods that offer fine impedance control. Experimental results verify the design concepts using an electrode configuration that is compatible with a differential six-plate CPT system. The results include measurements of the compensated CPT link in isolation as well as an evaluation of compensation applied to an end-to-end system with a class-E amplifier and class-E rectifier.
The results show that multi-band operation significantly extends the spatial robustness of the system. Compared to single-band operation, there is a 50\% increase in the compensation gap range in the dual-band system. The choice between multi-band and single-band systems depends on application requirements: multi-band adaptive load compensation works well in systems with large spatial variations, while single-band suffices for applications with modest spatial variation and defined range constraints.