Capacitance Tuning Method for Maximum Output Power in Multiple-Transmitter Wireless Power Transfer System

Abstract

It is common knowledge that wireless power transfer (WPT) systems with multiple transmitters (Txs) and a single receiver (Rx) have robust efficiency against lateral misalignment. However, the unnecessary coupling among Txs in actual multi-Tx WPT systems causes transmission efficiency degradation, and then additional tuning work is required to adjust some system parameters, such as the phase or frequency of Tx sources. Moreover, the frequency-splitting phenomenon caused by over-coupling between the Txs and Rx still occurs in multi-Tx systems. Thus, output power degradation is inevitable in the over-coupled state. In this paper, we propose an optimal capacitance tuning method that is applicable to multi-Tx WPT systems. A multi-Tx WPT system tuned with the optimal capacitances, which are obtained from the critical coupling condition between Txs and Rx, not only compensates the inner coupling among Txs but also achieves the maximum output power in the over-coupled state. To verify the validity of the proposed method, we implemented two-and three-Tx and single Rx WPT systems and measured the output power of load with respect to the Rx position along the x-and y-axes. As a result, with the proposed method without any changes in the operating frequency or phase, the systems could deliver higher output power than the conventional phase-controlled system. In particular, with the proposed method, the systems maintained the constant maximum transmission efficiency of 80% in the over-coupled state. INDEX TERMS magnetic beamforming, multiple transmitter, maximum output power, optimal tuning, power transfer efficiency, transmission efficiency, wireless power transfer.

Effect of Additional Transmitting Coils on Transfer Distance in Multiple-Transmitter Wireless Power Transfer System

“…In addition, the critical coupling coefficient (k c,1 ) between the first Tx coil and Rx coil derived in [28] is given by using the coupling coefficient (k critical ) in a two-coil system [1] as…”

“…Similarly. In [28], an optimal tuning method for each resonant capacitor was studied to transfer a constant maximum power for the free positions of Rx.…”

Compensation capacitance tunings of wireless power transfer systems using artificial neural network

“…Methods to acquire maximum output power at resonant frequency have been proposed such as compensating the capacitances of Rx [3] and of both Tx and Rx [4]. WPT systems generally have a structure that contains ferrite shields.…”

Loss-Separation Strategy to Improve Efficiency of Wireless High-Power Transfer Systems in Weak-Coupling Conditions

“…Recently, more complicated WPT systems have been proposed and attracted wide attentions such as multi-coils [17]- [19], multi-transmitters [20], multi-outputs [21], [22], etc. The multi-coil WPT systems can improve the power transfer efficiency compared to the conventional two-coil WPT systems [18].…”