Abstract
A new design approach is presented in this paper to show that under certain conditions, in a two-coil wireless power transfer system, the double-sided inductor-capacitor-capacitor (LCC) compensated wireless power transfer (LCC-WPT) system can be more energy efficient than the series-series (SS) compensated wireless power transfer (SS-WPT) system for the same load power, with special attention being paid to the effect that the parasitic coil and capacitor resistances have on the system efficiency. To make a fair comparison between the SS and LCC WPT systems, the direct current (DC) link voltage was adjusted to set equal load power for the two systems whilst using identical transmit and receive coils, coil-to-coil distance and load resistance. The system performance in terms of the system efficiency, the voltage stresses on the components, and the losses in the power devices were analysed for a practical system, comparing the LCC-WPT system and the SS-WPT system with respect to the load resistance. The effect of coil misalignment on the transferred power and efficiency for the two systems was compared. The theoretical proof and the conditions for meeting the objective are derived and practically verified in a two-coil WPT practical prototype, showing good agreement between analysis and experiments.
Highlights
Wireless power transfer (WPT) systems have been studied for a century since the great contribution made by Nikola Tesla in the early 1900s [1]
In [20], the authors analyse the difference between the SS and LCC WPT systems with tuned/mistuned coils in these two topologies, but the comparison is only in regard to efficiencies without considering the variation of the output power and the mistuning is caused by the variations of the relative position between primary and secondary sides; if there is no ferrite used in the system, the inductance of the coil will not change with the misalignment of the two coils, and the mistuning phenomenon will not occur
When the LCC-WPT system is tuned to have a constant resonant frequency, which means the input voltage VS and current ILf1 of the compensated primary coil-system are in phase and its amplitude is related to the relative coil-to-coil distance and load condition; the output current ILf2 is determined by the input voltage VS for a given system design and fixed load resistance; the output voltage U2 is in phase with the output current ILf2
Summary
Wireless power transfer (WPT) systems have been studied for a century since the great contribution made by Nikola Tesla in the early 1900s [1]. In [20], the authors analyse the difference between the SS and LCC WPT systems with tuned/mistuned coils in these two topologies, but the comparison is only in regard to efficiencies without considering the variation of the output power and the mistuning is caused by the variations of the relative position between primary and secondary sides; if there is no ferrite used in the system, the inductance of the coil will not change with the misalignment of the two coils, and the mistuning phenomenon will not occur. In order to obtain a clear understanding of the advantages and disadvantages of these two compensation topologies, a comparison between the SS-WPT system and double-sided LCC-WPT system was conducted to investigate the WPT system performance under the conditions of (a) same output power with different load resistance (b) coil-to-coil horizontal misalignment. Even though this paper only focused on the comparison between the SS-WPT system and the LCC-WPT system, the analysis concept was suitable for any comparison among different compensation topologies
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