Abstract
With the increase of charging requirements in electrical equipment, the wireless power transfer (WPT) system with multiple receivers has gained more attention as the charging power and efficiency of a WPT system depends on the equivalent reflected impedance of the load. Based on the circuit model analysis of a single receiver WPT system, this paper investigated the multiple-receiver WPT system. The relationship between the mutual inductance, load, and system efficiency was discussed and the optimal load, the equivalent reflected impedance, and power division method were analyzed to design the proposed system control scheme. With the use of the perturbation and observation (P&O) algorithm control method, the current of transfer and receivers were regulated to achieve stable constant power charging. Furthermore, when searching the minimum input power of the system, the optimal efficiency under a fixed power division ratio was also received. The validity of the proposed system control method was confirmed by simulation and experimental results. Under the proposed control method, an efficiency above 80% can be achieved for a multiple-receiver WPT system with a fixed power division ratio working at 6.78 MHz.
Highlights
Wireless power transfer (WPT) systems for consumer electronic devices such as mobile phones, wearable devices, and micro robots are gaining more attention [1,2,3]
This paper presents a power division and optimal efficiency tracking control method based on a 6.78 MHz system
The results showed that the maximum efficiency of A4WP products was 72%, while with the proposed control method, the system efficiency exceeded 80%
Summary
Wireless power transfer (WPT) systems for consumer electronic devices such as mobile phones, wearable devices, and micro robots are gaining more attention [1,2,3]. In a multi-receiver wireless power transfer system, the receiving devices may have many different sizes, positions, load characteristics, and power requirements. There have been relatively few studies on multiple-receiver WPT systems. References [9,10] analyzed the efficiency of multiple-receiver systems under different conditions, but failed to propose power division and methods of efficiency improvement. The authors in Reference [11] proposed a method for designing circuit parameters based on different receivers and used the frequency tracking method to compensate for the system efficiency. It did not control the power assigned to each receiver
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