다중소스를 사용하는 무선전력전송 시스템에 관한 연구

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, there still remain curious things such as practical improvements of transmission distance and covering clear area according to the number of Txs. In addition, 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 thesis, the practical performance and novel method for maximum power transfer in multi-Tx WPT system based on system efficiency and transmission efficiency are derived. First, from the point of system efficiency, the practical improvement of transmission distance and covering area according to the number of Tx coils in multi-Tx WPT system is clearly analyzed. Moreover, the analyzed results that the general multi-Tx system with none of overlapped Txs cannot increase practical transmission distance between Txs and Rx are demonstrated. From the point of transmission efficiency, an free resonant frequency tuning method that is applicable to multi-Tx WPT systems is derived. 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, the two-and three-Tx and single Rx WPT systems were implemented and the output power of load was measured 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.