Energy efficiency characteristic analysis of tri-coil PT symmetric MC-WPT systems

The parity-time (PT) symmetric magnetic coupling wireless power transfer (MC-WPT) system has received a great deal of attention since it was proposed. Its transmission efficiency has been greatly improved when compared with previous research. The operational amplifier (OA) is a typical construction method for PT symmetric MC-WPT systems. On this basis, to achieve a higher transmission efficiency and a longer effective power transmission distance at the same time, this paper constructs an OA-based tri-coil PT symmetric MC-WPT system. The analytical expressions of its singularity, PT symmetric state, and PT symmetric broken state are obtained. Then a complete set of parameter design criteria for the tri-coil PT symmetric system is derived. The transmission efficiency and resonant frequency of two-coil and tri-coil system are simulated on MATLAB software, and the simulation results are consistent with the theoretical analysis results. Finally, an experimental device is constructed to further verify the correctness of the theory. This paper demonstrates that the effective power transmission distance of the tri-coil PT symmetric MC-WPT system is more than twice that of the two-coil PT symmetric MC-WPT system, which can achieve a good balance between transmission efficiency and transmission distance.