Research Of High Frequency Low Power Omnidirectional Wireless Power Transfer System

Since the publication of the research of wireless power transfer(WPT)via coupled magnetic resonance by the researchers from MIT in 2007,researchers worldwide have devoted to the research of wireless power transfer.Thanks to the development of the field of consumer electronics,electric vehicles and medical equipment,this mid-range wireless power transfer technology has a huge application requirements and prospect.The energy efficiency,transferred power and misalignment tolerance are key performance indices of the WPT system.However,the movement and misalignment of the receiver is inevitable in some specific application,such as wearable or portable devices,biomedical implants and RFID,and thus many omnidirectional WPT s ystems are introduced.For improving the performance of the WPT system and extending the range of efficient power transfer,a novel omnidirectional WPT system is proposed in this paper.The proposed system utilizes the orthogonal transmit coils to extend the range of efficient power transfer,and employs an additional source coil for each orthogonal transmit coil to increase the input impedance of the system.To realize the omnidirectional power transfer,conventional omnidirectional WPT system establish a rotating magnetic field by directly controlling the current of the transmit coil.A voltage phase control method is proposed in this paper.This method replaces the current input to the voltage input and is simpler and more reliable.By modeling and analyzing the conventional and novel omnidirectional WPT system,the condition of higher maximum efficiency of novel system compared with that of the conventional one is deduced.The simulated and experimental results show that the energy efficiency of the proposed system could reach 85% and is much higher than the conventional counterpart in any direction when the condition is satisfied.Moreover,compared with the conventional system,the variation of the load and movement of the receiver have less impacts on the proposed system,which means that the efficiency stability of the proposed system is higher.Finally,the misalignment tolerance of the proposed omnidirectional WPT system is analyzed in this paper.The influence of angular and lateral misalignment on t he proposed system is studied by simulation and experiment.The simulated and experimental results show that the energy efficiency of above 75% for the entire range of 360° of angular misalignment can be achieved.