Abstract:The two-stage charging mode can solve the problem of both CC overcharge and CV undercharge during the battery charging process. At present, there are several ways to achieve CC/CV charging for WPT systems. The first one is the working frequency adjustment. The second one is the duty cycle adjustment, and the third one is that a DC-DC chopper is added at the secondary side. The above three methods can achieve CC/CV charging with high control accuracy, but their control schemes are too complex. Moreover, the output current and the output voltage fluctuate greatly during the charging mode switching. The spike will impact the battery on the battery life. In view of the shortcomings of the above literature, this paper proposes a LCC-LCC/S self-switching CC and CV composite topology, which only requires two AC switches and a compensation capacitor on the secondary side. By simultaneously opening and closing the two AC switches, the proposed WPT system can not only achieve the segmented CC and CV charging, but also effectively improve the system safety under abnormal working conditions, The proposed composite WPT system can also achieve ZPA in both CC and CV charging modes, and the output voltage and the output current fluctuate are very small for the duration of the switches switching. At last, the performance evaluation is also given by comparing the LCC-LCC/S topology with SS/PS hybrid topology. Firstly, the self-switching LCC-LCC/S-based composite topology is presented, and the characteristics of both CC/CV and ZPA, together with the load optimal switching point, are also analyzed. Secondly, several abnormal working conditions including the secondary side missing, load short-circuit, and load open-circuit are analyzed, and the corresponding solutions are presented. Thirdly, by comparing the system characteristics of the currently popular S/SP topology, the advantages of the LCC-LCC/S topology are highlighted. Finally, an experimental platform is built to verify the theory and evaluate the system performance. The experimental results indicate that a high-efficient, reliable and safe WPT system is successfully manufactured with the transmission efficiency being 86%~92% during the whole charging process, the maximum current being 5.03A and the maximum voltage being 48.92V. The simulated and experimental results show that the LCC-LCC and the LCC-S topology can achieve load-independent CC and CV output with ZPA characteristics respectively. The output current changes only below 0.02A and the output voltage changes only below 0.2V during the charging mode switching. Therefore, they will not damage the battery. In order to improve charging safety and avoid the WPT system damage under abnormal operating conditions, the proposed WPT system can achieve the two charging mode freely switching on the LCC-LCC topology switching to the LCC-S topology in the case of the load open-circuit and the LCC-S topology switching to the LCC- LCC topology in the case of the load short circuit. And the voltage peak across the switches can be effectively reduced by controlling the switching sequence for the duration of the charging mode switching. Compared with the S/PS composite system, this composite system has higher efficiency and better anti-misalignments capability. The experimental WPT system can produce the maximum output voltage of 48.92V, the maximum output current of 5.03A, the maximum output power of 242.26W, and the efficiency of 86%~92%. The following conclusions can be drawn from the simulation and the experiments: (1) The proposed LCC-LCC/S composite topology can realizes two-stage CC/CV charging output, and effectively solves the problems of CC overcharge and CV undercharge. (2) The proposed system can effectively deal with abnormal working conditions such as secondary side missing, load short circuit, load open circuit, etc. And the WPT system can automatically run a low-power standby state without any control after the charging completion and the load removal. (3) Through the optimal control of the switching timing, the voltage spike across the switches is effectively reduced. (4) It is verified that the performance of the LCC-LCC/S topology on the anti-misalignments capability is better than that of the current popular S/PS composite topology.
杨云虎, 贾维娜, 梁大壮, 薛建志, 李钰. LCC-LCC/S自切换恒流恒压复合型无线电能传输系统[J]. 电工技术学报, 0, (): 44-44.
Yang Yunhu, Jia Weina, Liang Dazhuang, Xue Jianzhi, Li Yu. A Self-Switching WPT System Based on Hybrid Topology of LCC-LCC/S with Constant Current and Constant Voltage. Transactions of China Electrotechnical Society, 0, (): 44-44.
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