Abstract:
For magnetic resonant coupled wireless power transfer (WPT), the axial
movement of near-field coupled coils adversely degrades the power
transfer efficiency (PTE) of the system and often creates sub-resonance.
This paper presents a tunable impedance matching technique based on
optimum coupling tuning to enhance the efficiency of resonant coupled
WPT system. The optimum power transfer model is analysed from
equivalent circuit model via reflected load principle, and the adequate
matching are achieved through the optimum tuning of coupling coefficients
at both the transmitting and receiving end of the system. Both
simulations and experiments are performed to evaluate the theoretical
model of the proposed matching technique, and results in a PTE over
80% at close coil proximity without shifting the original resonant frequency.
Compared to the fixed coupled WPT, the extracted efficiency
shows 15.1% and 19.9% improvements at the centre-to-centre misalignment
of 10 and 70 cm, respectively. Applying this technique, the
extracted S21 parameter shows more than 10 dB improvements at both
strong and weak couplings. Through the developed model, the optimum
coupling tuning also significantly improves the performance over matching
techniques using frequency tracking and tunable matching circuits.
