Metal object detection method in wireless electric vehicle charging system
Kai DU1(),Guo-rong ZHU1,Jiang-hua LU2,*(),Mu-ye PANG1
1. School of Automation, Wuhan University of Technology, Wuhan 430070, China 2. School of Information Science and Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
A foreign object detection coil array that does not affect the power transmission capacity of the wireless power transmission (WPT) system and has no detection blind spots was proposed in view of the problem that metal foreign objects falling into the charging area of electric vehicles affect the electrical characteristics of the system and generate eddy current heating in order to ensure the safety and reliability of the WPT system. The detection coil resonance circuit and control circuit were designed to improve detection sensitivity and accuracy. An electric vehicle WPT system experimental prototype with metal foreign body detection function was built, and the effectiveness and feasibility of the detection method through more than ten common metal foreign bodies were verified. The test results verified that the output voltage of the detection circuit had obvious changes by removing the cans, paper clips and coins from the detection coil. The size and material of various metal foreign objects were different, and the output voltage change rate was different. The effectiveness of the proposed metal foreign body detection method was verified.
Kai DU,Guo-rong ZHU,Jiang-hua LU,Mu-ye PANG. Metal object detection method in wireless electric vehicle charging system. Journal of ZheJiang University (Engineering Science), 2022, 56(1): 56-62.
Fig.3Design rules of metal foreign body detection coil
Fig.4Detection coil resonance circuit
Fig.5Metal foreign body detection circuit
Fig.6Detection coil control logic
Fig.7Detection coil control circuit
Fig.8Timing control logic of metal foreign body detection circuit
Fig.93.3 kW experimental prototype of electric vehicle WPT system
Fig.10Control signal experimental waveform of foreign body detection circuit
Fig.11Test results of foreign body detection circuit output voltage
异物
Vg/%
25美分硬币
25.6
5美分硬币
21.4
1美分硬币
15.8
钥匙
31.3
铝片（3 cm×3 cm）
37.8
铜片（3 cm×3 cm）
41.2
螺母
4.7
螺栓
5.3
易拉罐
80.7
钢丝球
26.6
回形针
3.6
锡箔纸（2 cm×2 cm）
34.5
铁钉
4.2
Tab.1Impact of more than ten common metal foreign objects on output voltage of detection circuit
Fig.12Test results of detecting output voltage of coil resonance circuit
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