LCC-LCC/S自切换恒流-恒压复合型无线电能传输系统

A Self-Switching Wireless Power Transfer System Based on Hybrid Topology of LCC-LCC/S with Constant Current and Constant Voltage

为了解决蓄电池充电过程中的恒流过充或恒压欠充问题,该文提出一种LCC-LCC/S自切换恒流-恒压复合型无线电能传输系统。通过副边电力开关切换,该系统不仅可实现恒流-恒压输出,且能有效应对蓄电池充电过程中的各种异常工况;另外,在充电完成负载移除时,该系统能自动进入低功耗待机状态。首先,给出LCC-LCC/S自切换复合拓扑,分析恒压-恒流及零相角(ZPA)特性;其次,分析恒流-恒压切换点并验证其最优性;然后,通过分析充电过程中出现的副边缺失、负载短路、负载断路等异常工况,系统能通过开关切换有效应对以上异常工作情况,并且充电完成负载移除后系统能自动进入低功耗待机状态;接着,通过与目前研究较多的S-SP拓扑的系统特性进行对比,突出了LCC-LCC/S拓扑的优势;最后,搭建仿真和实验平台,实现最大电流为5.03 A、最大电压为48.92 V的高效率输出,验证了所提理论的正确性。

The two-stage charging mode can solve CC overcharge and CV undercharge during battery charging.There are several ways to achieve CC/CV charging for WPT systems,such as working frequency adjustment,duty cycle adjustment,and adding a DC-DC chopper at the secondary side.Such methods can achieve CC/CV charging with high accuracy,but their control schemes need to be simplified.Moreover,the output current and voltage fluctuate greatly during the charging mode switching.The spike will impact the battery on the battery life.Therefore,this paper proposes a LCC-LCC/S self-switching CC and CV composite topology,only requiring 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 achieve the segmented CC/CV charging and improve system safety under abnormal working conditions.Moreover,ZPA in both CC and CV charging modes can be realized,and the output voltage and current fluctuate very small during 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.The characteristics of CC/CV,ZPA,and the load optimal switching point are also analyzed.Secondly,several abnormal working conditions are analyzed,including the secondary side missing,load short-circuit,and load open-circuit.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.The experimental results indicate that a highly efficient,reliable and safe WPT system is manufactured.The transmission efficiency is 86%~92%during the charging process,the maximum current is 5.03 A,and the maximum voltage is 48.92 V.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 0.02 A,and the output voltage changes below 0.2 V during the charging mode switching.Therefore,they will not damage the battery.In order to improve charging safety and avoid WPT system damage under abnormal operating conditions,the proposed WPT system can achieve the two charging modes freely,switching the LCC-LCC topology to the LCC-S topology in the load open-circuit and the LCC-S topology to the LCC-LCC topology in the load short circuit.Moreover,the voltage peak across the switches can be effectively reduced by controlling the switching sequence for the duration of the charging mode switching.The proposed system has higher efficiency and better anti-misalignment capability than the S/PS composite system.The experimental WPT system can produce a maximum output voltage of 48.92 V,a maximum output current of 5.03 A,a maximum output power of 242.26 W,and an efficiency of 86%to 92%.The following conclusions can be drawn from the simulation and the experiments:(1)The proposed LCC-LCC/S composite topology can realize a two-stage CC/CV charging output and effectively solve CC overcharge and CV undercharge problems.(2)The proposed system can effectively deal with abnormal working conditions such as secondary side missing,load short circuit,and load open circuit.In addition,the WPT system can automatically run a low-power standby state without any control after the charging completion and the load removal.(3)The voltage spike across the switches is effectively reduced through the optimal control of the switching timing.(4)The performance of the LCC-LCC/S topology on the anti-misalignment capability is better than that of the current popular S/PS composite topology.