Abstract：Static wireless charging technology for electric vehicles (EV) have aroused extensive attention due to its safety and convenient. The key technologies of wireless charging of EV are analyzed in detail from the aspects of magnetic coupler, compensation networks, power electronics converters, and system modeling-optimization-robust control methods. In addition, hot issues and the future of static wireless charging technology for EV were discussed, aiming to point the way for the research of static wireless charging technology for EV.
[1] 赵争鸣, 张艺明, 陈凯楠. 磁耦合谐振式无线电能传输技术新进展[J]. 中国电机工程学报, 2013, 33(3): 1-13. Zhao Zhengming, Zhang Yiming, Chen Kainan.New progress of magnetically-coupled resonant wireless power transfer technology[J]. Proceedings of the CSEE, 2013, 33(3): 1-13. [2] 赵争鸣, 刘方, 陈凯楠. 电动汽车无线充电技术研究综述[J]. 电工技术学报, 2016, 31(20): 30-40. Zhao Zhengming, Liu Fang, Chen Kainan.New progress of wireless charging technology for electric vehicles[J]. Transactions of China Electrotechnical Society, 2016, 31(20): 30-40. [3] Budhia M, Covic G, Boys J.A new IPT magnetic coupler for electric vehicle charging systems[C]// IECON 36th Annual Conference on IEEE Industrial Electronics Society, Glendale, 2010: 2487-2492. [4] Patil D, Mcdonough M K, Miller J M, et al.Wireless power transfer for vehicular applications: overview and challenges[J]. IEEE Transactions on Trans- portation Electrification, 2018, 4(1): 3-37. [5] Budhia M, Covic G A, Boys J T.Design and optimization of circular magnetic structures for lumped inductive power transfer systems[J]. IEEE Transactions on Power Electronics, 2011, 26(11): 3096-3108. [6] Budhia M, Boys J T, Covic G A, et al.Development of a single-sided flux magnetic coupler for electric vehicle IPT charging systems[J]. IEEE Transactions on Industrial Electronics, 2013, 60(1): 318-328. [7] Nguyen T, Li S, Li W, et al.Feasibility study on bipolar pads for efficient wireless power chargers[C]// IEEE Applied Power Electronics Conference and Exposition (APEC), Fort Worth, 2014: 1676-1682. [8] Zaheer A, Kacprzak D, Covic G A.A bipolar receiver pad in a lumped IPT system for electric vehicle charging applications[C]//IEEE Energy Conversion Congress and Exposition (ECCE), Raleigh, 2012: 283-290. [9] Kim S, Covic G A, Boys J T.Tripolar pad for inductive power transfer systems for EV charging[J]. IEEE Transactions on Power Electronics, 2017, 32(7): 5045-5057. [10] Moon S, Kim B, Cho S, et al.Analysis and design of a wireless power transfer system with an intermediate coil for high efficiency[J]. IEEE Transactions on Industrial Electronics, 2014, 61(11): 5861-5870. [11] Choi S Y, Huh J, Lee W Y, et al.Asymmetric coil sets for wireless stationary EV chargers with large Lateral tolerance by dominant field analysis[J]. IEEE Transactions on Power Electronics, 2014, 29(12): 6406-6420. [12] Ahn S, Pak J, Song T, et al.Low frequency electromagnetic field reduction techniques for the on- line electric vehicle (OLEV)[C]//IEEE International Symposium on Electromagnetic Compatibility, Fort Lauderdale, 2010: 625-630. [13] Park C, Lee S, Jeong S Y, et al.Uniform power I-type inductive power transfer system with DQ power supply rails for on-line electric vehicles[J]. IEEE Transactions on Power Electronics, 2015, 30(11): 6446-6455. [14] Lee W Y, Huh J, Choi S Y, et al.Finite-width magnetic mirror models of mono and dual coils for wireless electric vehicles[J]. IEEE Transactions on Power Electronics, 2013, 28(3): 1413-1428. [15] Shin J, Shin S, Kim Y, et al.Design and implementation of shaped magnetic-resonance-based wireless power transfer system for roadway-powered moving electric vehicles[J]. IEEE Transactions on Industrial Electronics, 2014, 61(3): 1179-1192. [16] Chigira M, Nagatsuka Y, Kaneko Y, et al.Small-size light-weight transformer with new core structure for contactless electric vehicle power transfer system[C]// IEEE Energy Conversion Congress and Exposition, Phoenix, 2011: 260-266. [17] Takanashi H, Sato Y, Kaneko Y, et al.A large air gap 3kW wireless power transfer system for electric vehicles[C]//IEEE Energy Conversion Congress and Exposition (ECCE), Raleigh, 2012: 269-274. [18] Zhang Wei, White J C, Abraham A M, et al.Loosely coupled transformer structure and interoperability study for EV wireless charging systems[J]. IEEE Transactions on Power Electronics, 2015, 30(11): 6356-6367. [19] 胡超. 电动汽车无线供电电磁耦合机构能效特性及优化方法研究[D]. 重庆: 重庆大学, 2015. [20] 陈振伟. 电动汽车非接触充电系统用松耦合变压器设计与实现[D]. 哈尔滨: 哈尔滨工业大学, 2014. [21] 张献, 杨庆新, 崔玉龙, 等. 大功率无线电能传输系统能量发射线圈设计、优化与验证[J]. 电工技术学报, 2013, 28(10): 12-18. Zhang Xian, Yang Qingxin, Cui Yulong, et al.Design optimization and verification on the power transmitting coil in the high-power wireless power transmission system[J]. Transactions of China Elec- trotechnical Society, 2013, 28(10): 12-18. [22] 谭林林, 黄学良, 赵俊锋, 等. 一种无线电能传输系统的盘式谐振器优化设计[J]. 电工技术学报, 2013, 28(8): 1-6. Tan Linlin, Huang Xueliang, Zhao Junfeng, et al.Optimization design for disc resonators of a wireless power transmission system[J]. Transactions of China Electrotechnical Society, 2013, 28(8): 1-6. [23] Wei Ni, Collings I B, Xin Wang, et al.Radio alignment for inductive charging of electric vehicles[J]. IEEE Transactions on Industrial Informatics, 2015, 11(2): 427-440. [24] Ahmad A, Alam M S, Chabaan R.A comprehensive review of wireless charging technologies for electric vehicles[J]. IEEE Transactions on Transportation Electrification, 2018, 4(1): 38-63. [25] Bi Z, Kan T, Mi C C, et al.A review of wireless power transfer for electric vehicles: prospects to enhance sustainable mobility[J]. Applied Energy, 2016, 179: 413-425. [26] Sohn Y H, Choi B H, Lee E S, et al.General unified analyses of two-capacitor inductive power transfer systems: equivalence of current-source ss and sp compensations[J]. IEEE Transactions on Power Electronics, 2015, 30(11): 6030-6045. [27] Wang C S, Covic G A, Stielau O H.Power transfer capability and bifurcation phenomena of loosely coupled inductive power transfer systems[J]. IEEE Transactions on Industrial Electronics, 2004, 51(1): 148-157. [28] 周雯琪, 马皓, 何湘宁. 感应耦合电能传输系统不同补偿拓扑的研究[J]. 电工技术学报, 2009, 24(1): 133-139. Zhou Wenqi, Ma Hao, He Xiangning.Investigation on different compensation topologies in inductively coupled power transfer system[J]. Transactions of China Electrotechnical Society, 2009, 24(1): 133-139. [29] 孙跃, 夏晨阳, 戴欣, 等. 感应耦合电能传输系统互感耦合参数的分析与优化[J]. 中国电机工程学报, 2010, 30(33): 44-50. Sun Yue, Xia Chenyang, Dai Xin, et al.Analysis and optimization of mutual inductance for inductively coupled power transfer system[J]. Proceedings of the CSEE, 2010, 30(33): 44-50. [30] 李阳, 董维豪, 杨庆新, 等. 过耦合无线电能传输功率降低机理与提高方法[J]. 电工技术学报, 2018, 33(14): 3177-3184. Li Yang, Dong Weihao, Yang Qingxin, et al.Mechanism of power decreasing and improvement method for wireless power transfer system in over coupled regime[J]. Transactions of China Electro- technical Society, 2018, 33(14): 3177-3184. [31] Aditya K, Williamson S S.Comparative study of series-series and series-parallel compensation topo- logies for electric vehicle charging[C]//IEEE 23rd International Symposium on Industrial Electronics (ISIE), Istanbul, 2014: 426-430. [32] 孙跃, 廖志娟, 叶兆虹, 等. 基于振动理论的MCR-WPT系统频率分裂特性研究[J]. 电工技术学报, 2018, 33(13): 3140-3148. Sun Yue, Liao Zhijuan, Ye Zhaohong, et al.Research on frequency splitting characteristic of MCR-WPT systems based on vibration theory[J]. Transactions of China Electrotechnical Society, 2018, 33(13): 3140-3148. [33] Feng Hao, Cai Tao, Duan Shanxu, et al.A dual- side-detuned series-series compensated resonant converter for wide charging region in a wireless power transfer system[J]. IEEE Transactions on Industrial Electronics, 2018, 65(3): 2177-2188. [34] Wang C S, Covic G A, Stielau O H.Investigating an LCL load resonant inverter for inductive power transfer applications[J]. IEEE Transactions on Power Electronics, 2004, 19(4): 995-1002. [35] Borage M, Tiwari S, Kotaiah S.Analysis and design of an LCL-T resonant converter as a constant-current power supply[J]. IEEE Transactions on Industrial Electronics, 2005, 52(6): 1547-1554. [36] Kissin M, Huang C, Covic G A, et al.Detection of the tuned point of a fixed-frequency LCL resonant power supply[J]. IEEE Transactions on Power Electronics, 2009, 24(4): 1140-1143. [37] Keeling N A, Covic G A, Boys J T.A unity-power- factor IPT pickup for high-power applications[J]. IEEE Transactions on Industrial Electronics, 2010, 57(2): 744-751. [38] Madawala U K, Thrimawithana D J.A bidirectional inductive power interface for electric vehicles in V2G systems[J]. IEEE Transactions on Industrial Elec- tronics, 2011, 58(10): 4789-4796. [39] Villa J L, Sallan J, Sanz Osorio J F, et al. High-misalignment tolerant compensation topology for ICPT systems[J]. IEEE Transactions on Industrial Electronics, 2012, 59(2): 945-951. [40] Li Weihan, Zhao Han, Li Siqi, et al.Integrated LCC compensation topology for wireless charger in electric and plug-in electric vehicles[J]. IEEE Transactions on Industrial Electronics, 2015, 62(7): 4215-4225. [41] Li Siqi, Li Weihan, Deng Junjun, et al.A double- sided LCC compensation network and its tuning method for wireless power transfer[J]. IEEE Transactions on Vehicular Technology, 2015, 64(6): 2261-2273. [42] Zhang Wei, Mi C C.Compensation topologies of high- power wireless power transfer systems[J]. IEEE Transactions on Vehicular Technology, 2016, 65(6): 4768-4778. [43] Kan T, Nguyen T, White J C, et al.A new integration method for an electric vehicle wireless charging system using LCC compensation topology: analysis and design[J]. IEEE Transactions on Power Electronics, 2017, 32(2): 1638-1650. [44] Samanta S, Rathore A K.A new current-fed CLC transmitter and LC receiver topology for inductive wireless power transfer application: analysis, design, and experimental results[J]. IEEE Transactions on Transportation Electrification, 2015, 1(4): 357-368. [45] Wang Yijie, Yao Yousu, Liu Xiaosheng, et al.S/CLC compensation topology analysis and circular coil design for wireless power transfer[J]. IEEE Transactions on Transportation Electrification, 2017, 3(2): 496-507. [46] Kan Tianze, Lu Fei, Nguyen T, et al.Integrated coil design for EV wireless charging systems using LCC compensation topology[J]. IEEE Transactions on Power Electronics, 2018, 33(11): 9231-9241. [47] 周豪, 姚钢, 赵子玉, 等. 基于LCL谐振型感应耦合电能传输系统[J]. 中国电机工程学报, 2013, 33(33): 9-16. Zhou Hao, Yao Gang, Zhao Ziyu, et al.LCL resonant inductively coupled power transfer systems[J]. Proceedings of the CSEE, 2013, 33(33): 9-16. [48] Liu Fong, Zhang Yiming, Chen Kainan, et al.A comparative study of load characteristics of resonance types in wireless transmission systems[C]// IEEE Asia-Pacific International Symposium on Electromagnetic Compatibility (APEMC), Shenzhen, 2016: 203-206. [49] Qu Xiaohui, Han Hongdou, Wong Siu-chang, et al.Hybrid IPT topologies with constant current or constant voltage output for battery charging appli- cations[J]. IEEE Transactions on Power Electronics, 2015, 30(11): 6329-6337. [50] Li H L, Hu A P, Covic G A.A direct AC-AC converter for inductive power-transfer systems[J]. IEEE Transactions on Power Electronics, 2012, 27(2): 661-668. [51] Xuan Bac N, Vilathgamuwa D M, Madawala U K.A SiC-based matrix converter topology for inductive power transfer system[J]. IEEE Transactions on Power Electronics, 2014, 29(8): 4029-4038. [52] Moghaddami M, Anzalchi A, Sarwat A I.Single- stage three-phase AC-AC matrix converter for inductive power transfer systems[J]. IEEE Transactions on Industrial Electronics, 2016, 63(10): 6613-6622. [53] Weerasinghe S, Madawala U K, Thrimawithana D J.A matrix converter-based bidirectional contactless grid interface[J]. IEEE Transactions on Power Electronics, 2017, 32(3): 1755-1766. [54] Kusumah P P, Kyyra J.Minimizing coil power loss in a direct AC/AC converter-based contactless electric vehicle charger[C]//IEEE 19th European Conference on Power Electronics and Applications (EPE'17 ECCE Europe), Warsaw, 2017: 1-10. [55] Kusumah F P, Kyyra J.Bi-directional power transfer of a contactless electric vehicle charger using direct three-phase to single-phase AC/AC converter[C]// IEEE 20th European Conference on Power Electro- nics and Applications (EPE'18 ECCE Europe), Riga, 2018: 1-10. [56] Kusumah F P, Vuorsalo S, Kyyra J.A direct three-phase to single-phase AC/AC converter for contactless electric vehicle charger[C]//2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe), Geneva, 2015: 1-10. [57] Kusumah F P, Vuorsalo S, Kyyra J.Components selection of a direct three-phase to single-phase AC/AC converter for a contactless electric vehicle charger[C]//The18th European Conference on Power Electronics and Applications (EPE'16 ECCE Europe), Karlsruhe, 2016: 1-10. [58] Samanta S, Rathore A K.A new inductive power transfer topology using direct AC-AC converter with active source current waveshaping[J]. IEEE Transa- ctions on Power Electronics, 2018, 33(7): 5565-5577. [59] 黄雅琪. 应用于无线输电系统的单相单级AC-AC谐振变换器[D]. 广州: 华南理工大学, 2018. [60] Kurs A, Karalis A, Moffatt R, et al.Wireless power transfer via strongly coupled magnetic resonances[J]. Science, 2007, 317(5834): 83-86. [61] Li Hongchang, Wang Kangping, Huang Lang, et al.Dynamic modeling based on coupled modes for wireless power transfer systems[J]. IEEE Transa- ctions on Power Electronics, 2015, 30(11): 6245-6253. [62] 疏许健, 张波. 感应耦合无线电能传输系统的能量法模型及特性分析[J]. 电力系统自动化, 2017, 41(2): 28-32. Shu Xujian, Zhang Bo.Energy model and characteri- stic analysis for inductively coupled power transfer system[J]. Automation of Electric Power Systems, 2017, 41(2): 28-32. [63] 黄学良, 曹伟杰, 周亚龙, 等. 磁耦合谐振系统中的两种模型对比探究[J]. 电工技术学报, 2013, 28(增刊2): 13-17. Huang Xueliang, Cao Weijie, Zhou Yalong, et al.Comparative study on the two kinds of models in the technology of magnetic coupling resonance system[J]. Transactions of China Electrotechnical Society, 2013, 28(S2): 13-17. [64] Kiani M, Ghovanloo M.The circuit theory behind coupled-mode magnetic resonance-based wireless power transmission[J]. IEEE Transactions on Circuits and Systems I: Regular Papers, 2012, 59(9): 2065-2074. [65] 张波, 黄润鸿, 疏许健. 无线电能传输原理[M]. 北京: 科学出版社, 2018. [66] 傅文珍, 张波, 丘东元. 频率跟踪式谐振耦合电能无线传输系统研究[J]. 变频器世界, 2009(8): 41-46. Fu Wenzhen, Zhang Bo, Qiu Dongyuan.Study on frequence-tracking wireless power transfer system by resonant coupling[J]. The World of Inverters, 2009(8): 41-46. [67] Sample A P, Meyer D A, Smith J R.Analysis, experimental results, and range adaptation of magnetically coupled resonators for wireless power transfer[J]. IEEE Transactions on Industrial Electro- nics, 2011, 58(2): 544-554. [68] Zhang Yiming, Zhao Zhengming.Frequency splitting analysis of two-coil resonant wireless power transfer[J]. IEEE Antennas and Wireless Propagation Letters, 2014, 13: 400-402. [69] Huang Runhong, Zhang Bo, Qiu Dongyuan, et al.Frequency splitting phenomena of magnetic resonant coupling wireless power transfer[J]. IEEE Transa- ctions on Magnetics, 2014, 50(11): 1-4. [70] Zhang Yiming, Zhao Zhengming, Chen Kainan.Frequency-splitting analysis of four-coil resonant wireless power transfer[J]. IEEE Transactions on Industry Applications, 2014, 50(4): 2436-2445. [71] 张献, 杨庆新, 陈海燕, 等. 电磁耦合谐振式传能系统的频率分裂特性研究[J]. 中国电机工程学报, 2012, 32(9): 167-173. Zhang Xian, Yang Qingxin, Chen Haiyan, et al.Research on characteristics of frequency splitting in electromagnetic[J]. Proceedings of the CSEE, 2012, 32(9): 167-173. [72] Li Hongchang, Fang J, Tang Y.Dynamic phasor- based reduced order models of wireless power transfer systems[J]. IEEE Transactions on Power Electronics, 2015, 30(11): 6245-6253. [73] Swain A K, Neath M J, Madawala U K, et al.A dynamic multivariable state-space model for bidirectional inductive power transfer systems[J]. IEEE Transactions on Power Electronics, 2012, 27(11): 4772-4780. [74] 林天仁, 李勇, 麦瑞坤. 基于LCL-S拓扑的感应电能传输系统的建模与控制方法[J]. 电工技术学报, 2018, 33(1): 104-111. Lin Tianren, Li Yong, Mai Ruikun.Modeling and control method of inductive power transfer system based on LCL-S topology[J]. Transactions of China Electrotechnical Society, 2018, 33(1): 104-111. [75] Zahid Z U, Dalala Z, Lai J.Small-signal modeling of series-series compensated induction power transfer system[C]//IEEE Applied Power Electronics Con- ference and Exposition (APEC), Fort Worth, 2014: 2847-2853. [76] Zhou Jiali, Zhang Bo, Xiao Wenxun, et al.Nonlinear parity-time-symmetric model for constant efficiency wireless power transfer: application to a drone-in- flight wireless charging platform[J]. IEEE Transa- ctions on Industrial Electronics, 2019, 66(5): 4097-4107. [77] Lee S, Choi B, Rim C T.Dynamics characterization of the inductive power transfer system for online electric vehicles by Laplace phasor transform[J]. IEEE Transactions on Power Electronics, 2013, 28(12): 5902-5909. [78] Li Hongchang, Wang Kangping, Huang Long, et al.Dynamic modeling based on coupled modes for wireless power transfer systems[J]. IEEE Transa- ctions on Power Electronics, 2015, 30(11): 6245-6253. [79] Li Hongchang, Fang Jingyang, Chen Shuxin, et al.Pulse density modulation for maximum efficiency point tracking of wireless power transfer systems[J]. IEEE Transactions on Power Electronics, 2018, 33(6): 5492-5501. [80] Song Kai, Li Zhenjie, Jiang Jinhai, et al.Constant current/voltage charging operation for series-series and series-parallel compensated wireless power transfer systems employing primary-side controller[J]. IEEE Transactions on Power Electronics, 2018, 33(9): 8065-8080. [81] Lovison G, Sato M, Imura T, et al.Secondary- side-only simultaneous power and efficiency control for two converters in wireless power transfer system[C]// IEEE IECON 2015-41st Annual Conference of the IEEE Industrial Electronics Society, Yokohama, 2015: 4824-4829. [82] Li Hongchang, Li Jie, Wang Kongping, et al.A maximum efficiency point tracking control scheme for wireless power transfer systems using magnetic resonant coupling[J]. IEEE Transactions on Power Electronics, 2015, 30(7): 3998-4008. [83] Li Zhenjie, Song Kai, Jiang Jinhai, et al.Constant current charging and maximum efficiency tracking control scheme for supercapacitor wireless charging[J]. IEEE Transactions on Power Electronics, 2018, 33(10): 9088-9100. [84] Yeo T, Kwon D, Khang S, et al.Design of maximum efficiency tracking control scheme for closed-loop wireless power charging system employing series resonant tank[J]. IEEE Transactions on Power Electronics, 2017, 32(1): 471-478. [85] Dai Xin, Li Xiaofei, Li Yanling, et al.Maximum efficiency tracking for wireless power transfer systems with dynamic coupling coefficient estimation[J]. IEEE Transactions on Power Electronics, 2018, 33(6): 5005-5015. [86] 刘帼巾, 李义鑫, 崔玉龙, 等. 基于FPGA的磁耦合谐振式无线电能传输频率跟踪控制[J]. 电工技术学报, 2018, 33(14): 3185-3193. Liu Guojin, Li Yixin, Cui Yulong, et al, Frequency tracking control of wireless power transfer via magnetic resonance coupling based on FPGA[J]. Transactions of China Electrotechnical Society, 2018, 33(14): 3185-3193. [87] Mai Raikun, Liu Yeyan, Li Yong, et al.An active-rectifier-based maximum efficiency tracking method using an additional measurement coil for wireless power transfer[J]. IEEE Transactions on Power Electronics, 2018, 33(1): 716-728. [88] Ling R, Wang L, Sun Y, et al.A second-order sliding-mode controller for inductively coupled power transfer systems[C]//IECON 2017-43rd Annual Conference of the IEEE Industrial Electronics Society, Beijing, 2017: 6497-6503. [89] Yang Yun, Zhong Wenxing, Kiratipongvoot S, et al.Dynamic improvement of series-series compensated wireless power transfer systems using discrete sliding mode control[J]. IEEE Transactions on Power Electronics, 2018, 33(7): 6351-6360. [90] 戴欣, 余奎, 孙跃. CLC谐振型感应电能传输系统的H∞ 控制[J]. 中国电机工程学报, 2010, 30(30): 47-54. Dai Xin, Yu Kui, Sun Yue.Study on H∞ control method for CLC resonant inductive power transfer system[J]. Proceedings of the CSEE, 2010, 30(30): 47-54. [91] 戴欣, 周继昆, 孙跃. 具有频率不确定性的π 型谐振感应电能传输系统H∞ 控制方法[J]. 中国电机工程学报, 2011, 31(30): 45-53. Dai Xin, Zhou Jikun, Sun Yue.H∞ Control method with frequency uncertainty for π type resonant inductive power transfer system[J]. Proceedings of the CSEE, 2011, 31(30): 45-53. [92] 王理智. 感应耦合电能传输系统高阶滑模控制算法的研究[D]. 重庆: 重庆大学, 2017. [93] 罗博, 陈丽华, 李勇, 等. 基于滑模控制的感应耦合电能传输系统输出电压控制研究[J]. 电工技术学报, 2017, 32(23): 235-242. Luo Bo, Chen Lihua, Li Yong, et al.Investigation of output voltage control for the inductive power transfer system based on sliding mode control theory[J]. Transactions of China Electrotechnical Society, 2017, 32(23): 235-242. [94] Assawaworrarit S, Yu Xiaofang, Fan Shanhui.Robust wireless power transfer using a nonlinear parity- time-symmetric circuit[J]. Nature, 2017, 546(7658): 387-390. [95] 疏许健, 张波. 降低整数阶无线电能传输谐振频率的分数阶方法[J]. 电工技术学报, 2017, 32(18): 83-89. Shu Xujian, Zhang Bo.A fractional-order method to reduce the resonant frequency of integer-order wireless power transmission system[J]. Transactions of China Electrotechnical Society, 2017, 32(18): 83-89. [96] Jiang Yanwei, Zhang Bo.High-power fractional- order capacitor with 1<α<2 based on power converter[J]. IEEE Transactions on Industrial Electronics, 2018, 65(4): 3157-3164. [97] Shu Xujian, Zhang Bo.The effect of fractional orders on the transmission power and efficiency of fractional- order wireless power transmission system[J]. Energies, 2018, 11(7): 1774-1782.
2020, Vol. 35 
