Transactions of China Electrotechnical Society  2023, Vol. 38 Issue (24): 6581-6595    DOI: 10.19595/j.cnki.1000-6753.tces.221733
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Targeted Power Transfer Method for Omnidirectional Wireless Power Transfer System Based on Mutual Inductance Identification and Phase-Shift Angle Optimization
Feng Tianxu1, Shi Ke1, Sun Yue2, Wang Peiyue1, Jiang Jincheng1
1. College of Automation Chongqing University of Posts and Telecommunications Chongqing 400065 China;
2. College of Automation Chongqing University Chongqing 400044 China

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Abstract  The omnidirectional wireless power transfer(WPT) technology is favored by scholars at home and abroad because of its good anti-positional and angular misalignment performance. The efficiency of an omnidirectional WPT system can be improved by pointing the synthetic magnetic field generated by the omnidirectional transmitter to the receiver. It is necessary to detect the receiver's orientation and control the transmitter's excitation current in realtime. However, effective methods to identify the orientation of the receiver and adjust the excitation current are needed. To this end, an omnidirectional WPT system targeted power transfer method based on mutual inductance identification and phase-shift angle optimization is proposed. In this method, the orientation of the “target” (i.e., the receiver) is indirectly determined by mutual inductance identification, and the excitation current required for targeted power transmission is obtained by phase-shift angle optimization. This method can realize the maximum efficiency transmission of the magnetic coupler. Besides, it does not need to detect the orientation of the receiver or a communication link.
This paper uses the composite planar coil to illustrate the proposed targeted power transfer method because of its omnidirectional power transmitting capability and saving installation space advantages. The composite plane coil structure is composed of three transmitting coils (two crossed 8-shaped coils and a circular coil), and it is used as the transmitter, while a disc coil works as the receiver. To control the excitation current of the three transmitting coils separately, three independent inverters with phase-shift control are used to drive the three transmitting coils. The LCC compensation network and series compensation capacitor are used on the primary and secondary sides. Then, the relationship between the magnetic coupler efficiency, mutual inductance, and phase shift angle is derived. An omnidirectional WPT system targeted power transfer method is proposed based on mutual inductance identification and phase-shift angle optimization. In mutual inductance identification, the inverter is excited separately and cooperatively to identify the size of mutual inductance and the symbol of mutual inductance. In phase-shift angle optimization, the maximum efficiency is taken as the optimization objective, and the optimal phase-shift angle is obtained by solving the extreme value of the ternary function. Finally, the flowchart of the mutual inductance identification and phase-shift angle optimization is given.
A 100 W-level experimental setup is built to verify the effectiveness of the proposed method. The working principle of the proposed targeted power transfer method is further expounded experimentally from three angular misalignments of the receiver. The power and efficiency of the receiver measured under three angular misalignments are 81 W-86.6%, 96 W-87.1%, and 94 W-84.7%, respectively. Besides, three rotation types and three offset types of the receiver are selected to test the omnidirectional powering performance. The rotational method and the same current excitation method are introduced to compare with the proposed directional method. The experimental results show that the same current excitation method cannot achieve omnidirectional powering, and the efficiency of the directional method is at least 10% higher than that of the rotational method. The dc-dc efficiency of the proposed system is more than 80% when the receiver moves or rotates arbitrarily within ±60 mm. The proposed system and method are promising for applying multi-degree-of-freedom wireless charging of mobile electronic devices, such as smartphones and tablets.
Key wordsWireless power transfer      omnidirectional targeted power transfer      mutual inductance identi- fication      phase-shift angle optimization     
Received: 13 September 2022     
PACS: TM724  
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Feng Tianxu
Shi Ke
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Jiang Jincheng
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Feng Tianxu,Shi Ke,Sun Yue等. Targeted Power Transfer Method for Omnidirectional Wireless Power Transfer System Based on Mutual Inductance Identification and Phase-Shift Angle Optimization[J]. Transactions of China Electrotechnical Society, 2023, 38(24): 6581-6595.
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