Magnetic Field Analysis and Excitation Currents Optimization for an Omnidirectional WPT System Based on Three-Phase Tubular Coils

This article proposes an omnidirectional wireless power transfer system for powering up electronic devices inside a tubular structure, which has good received voltage stability (RVS) no matter how the receiving coil self-rotates on its own axis or revolves around the z-axis. Three-phase tubular coils are taken as the transmitter at the primary side, and a circular coil works as the receiver at the secondary side. Based on a three-phase half-bridge inverter and inductor capacitor capacitor-series (LCC-S) compensated topology, the expression of the received voltage is derived. To achieve the best RVS, the rotating magnetic field of the transmitter is modeled theoretically, and the essence of the RVS under angular misalignment of the receiver is analyzed. The phase difference of excitation currents is optimized to achieve the best RVS under two typical connection types of the transmitter. The finite-element method simulations are conducted to obtain the magnetic field distribution and the relationship between the received voltage and rotation angle. Finally, the experimental results show that the received voltage pulsation can be efficiently reduced within ±15.6% under arbitrary angular misalignment of the receiver.