The Research Of Self-tuning Technology For Wireless Power Transfer Via Coupled Magnetic Resonances

As a new concept of energy transmission, wireless power transfer via coupled magnetic resonances(CMR) overcomes the shortages of traditional inductive coupling power transmission. It is able to transfer power with high efficiency over distances in several meters and can be employed for a wide range of applications, such as wireless powering for embedded fault diagnosis system, wireless charging for mobile terminal device and so on. However, the power transfer efficiency will drop dramatically when the system loses resonance due to some interference factors. In this paper, a self-tuning technology for wireless power transfer via CMR is studied. The main contents and conclusions of this thesis are as follows:1、The power waves-based method is innovatively introduced to modeling and analyzing the wireless power transfer system using CMR. The load power and the transfer power gain of the two-port network are analyzed. The maximum transfer power gain is obtained when the system satisfies the power matching condition. It is verified by numerical simulation method using MATLAB software.2、The two-port self-tuning method based on power matching condition is firstly introduced to improve the performance of the wireless power transfer system using CMR in domestic. The principles of the frequency-adjusted method and the matching network-adjusted method are studied. Then, the two-port self-tuning system and the one-port self-tuning system are designed using the matching network-adjusted method.3、The simulation circuit model of the wireless power transfer system using CMR is built. The self-tuning system based on the matching network-adjusted method proposed in this paper is simulated and analyzed when the model parameters vary. The results demonstrate that the transfer power gain of the system increases significantly after self-tuning and two-port self-tuning is better than one-port self-tuning.4、An experiment system for wireless power transfer via CMR is built. The system is made to lose resonance by changing the transmission distance and the load impedance. The experimental study on self-tuning using the matching network-adjusted method is carried out. The transfer power gains of the system before tuning and after tuning are analyzed. The results demonstrate that by using the network-adjusted method proposed in this paper, the system can be tuned to maintain resonance and obtain high transfer power gain even at a varying transmission distance or connecting with different loads. The self-tuning approach proposed in this paper is able to solve the problem that practical system is prone to lose resonance due to interference.