The Analysis for Selecting Compensating Capacitances of Two-Coil Resonant Wireless Power Transfer System

Transcription

1 Fist IEEE Intenational onfeence on Enegy Intenet The Analysis fo electing ompensating apacitances of Two-oil esonant Wieless Powe Tansfe ystem Hong Huan, Yang Dongsheng and Won okhui ollege of Infomation cience and Engineeing Notheasten Univesity henyang, hina Abstact In ecent yeas, magnetically coupled esonant becomes an intense eseach in the study of wieless powe tansfe (WPT. Based on the two-coil esonant wieless powe tansfe system, this pape conducts eseach on the fou topology models using cicuit theoy. Fist, the fou topology models, which ae: eies-paallel (P, eies- eies (, Paallel-eies (P, Paallel-Paallel (PP, ae built to descibe the two-coil esonant WPT system. Next, the method of selecting compensating capacitances fo the pimay tansmitting coils ae deduced and pesented. Then the tansfe pefomance of these fou topology models ae analyzed and compaed, and the conclusion is pesented that Paallel-Paallel (PP models is the best choice fo a elatively fa distance wieless powe tansfe system since it has a elatively high tansfe powe and efficiency. Finally, the simulations in PPIE fo the fou topology models ae caied out, the esults validate the poposed conclusions. Keywods-Two oils, magnetically coupled esonant, selecting compensating capacitances, wieless powe tansfe(wpt I. INTODUTION As ealy as 9, the oatian Ameican physicist Nikola Tesla has conducted an expeiment to tansfe powe wielessly, which was inteupted fo lack of funds[]. Eve since then, wieless powe tansfe (WPT has become a hot eseach fields and aoused wide concen. In the past few decades, as taditional cable powe supply shows its defects and along with the development and populaization of the small mobile devices, geat attention has been paid to WPT[-5]. Typically, WPT can be classified into fou diffeent types[6-], namely, lase powe tansfe (PT, micowave powe tansfe (PT, inductively coupled powe tansfe (IPT, magnetically coupled esonant wieless powe tansfe (-WPT. Theeinto, PT has an advantage of oientation and enegy concentation, but it equies a high diectional accuacy, and it is not matue enough to widespead[6]. PT, which utilizes the fa field adiation effect of electomagnetic field to tansfe powe in fee space, can tansfe powe wielessly elatively fa apat and its atmospheic loss is elatively low, but it has a wide micowave divegence angle and low powe density[7]. IPT is a matue technology, which pats of the eseach achievements have been adopted in pactical applications, while its estictions on tansfe distance (only cm level and tansfe powe cannot meet people s expectation fo WPT commendably[8-]. As fo - WPT, it is fist put fowad and confimed by an expeiment by IT in 7[]. ince -WPT can tansfe powe wielessly elatively fa, which can each mete level, as well as high tansfe powe and efficiency, it becomes a hot eseach fo domestic and foeign scholas at pesent[,3]. Accoding to the diffeent connection types of inductance coil and compensating capacitance of tansmitting teminal and eceiving teminal, -WPT system can be classified into fou topology models [4], which ae eies-paallel (P, eies-eies (, Paallel- eies (P, Paallel-Paallel (PP. Howeve, less eseach has been done to analyze and compae the fou topology models, and the method about how to select the compensating capacitances fo each model is also seldom mentioned. efeence [5] analyzes and compaes the cicuit model and coupled-mode theoy fo -WPT with the model. efeence [6] makes a detailed and in-depth analysis fo the tansfe powe and tansfe efficiency of -WPT system. efeence [7] demonstates and explains the method of selecting compensating capacitances fo these fou models, wheeas it neglects to ensue the esonant situation of the WPT system. Theefoe, the main woks of this pape ae as follows: Based on the two-coil esonant WPT, the models of the fou topology ae built by using cicuit theoy; the method of selecting compensating capacitances fo each model ae deduced and obtained; the tansfe pefomance of the fou models ae analyzed and compaed, and the conclusion that PP model is the best choice fo a elatively fa distance WPT system is pesented since it has a elatively high tansfe powe and efficiency. Finally, the simulation of the fou models in PPIE is demonstated, and the esults validate the poposed conclusions. The detailed analysis and esults of the two-coil esonant WPT in this pape is a helpful and useful guiding fo designes to design a pactical two-coil esonant WPT system. II. ODEING AND ANAYZING FO EETING OPENATING APAITANE A. odeling the two-coil esonant WPT As depicted in Fig., a magnetically coupled esonant WPT system consists of diving souce, tansmitting coil, eceiving coil, compensating capacitances and load. Though the connection of the inductances with thei espective compensating capacitances, tansmitting coil can tansfe powe wielessly to eceiving coil in a magnetically coupled esonant situation, then the load can get powe fom eceiving coil[8] /7 $3. 7 IEEE DOI.9/IEI

2 Figue. The stuctue diagam of magnetically coupled esonant WPT system It should be pointed out that the compensating capacitances plays an impotance pat in maximizing the tansfe powe and efficiency and educing the eactive powe capacity of the WPT system[9]. Especially, accoding to the diffeent connection types of inductance coil and compensating capacitance of tansmitting teminal and eceiving teminal, -WPT system can be classified into fou topology models, which ae P model, model, P model and PP model as shown in Fig.. In the fou models of Fig., U is the diving souce, is the souce intenal esistance,, ae espectively the equivalent inductance of tansmitting teminal and eceiving teminal, and, ae the compensating capacitances fo and, is the equivalent load. U U (a P model U U (b model (c P model (d PP model Figue. Fou models of the two-coil magnetically coupled esonant WPT system U B. Analyzing the method of electing ompensating apacitances The fou models in Fig. can be abstacted to thei equivalent cicuits espectively as shown in Fig. 3. The tansmitting cicuit in Fig. 3 (a and (b is model, which means that the compensating capacitance is seies with inductance coil, and that in Fig. 3 (c and (d is P model, which means that the compensating capacitance is paallel with inductance coil. jω jω I (athe equivalent cicuit of P model U jω jω I U jω j ω (bthe equivalent cicuit of model U ji ω ji ω (cthe equivalent cicuit of P model (dthe equivalent cicuit of PP model Figue 3. The equivalent cicuits of the fou models As fo P model and model, accoding to Kichhoff s voltage law, mathematical equation of the models can be established as equation ( U = ZI jω I ( = jω I I Z The equation( can be futhe simplified to equation ( U = ( Z Z I jω ( I = I Z Whee Z is the impedance of the tansmitting cicuit, and Z is the impedance of the eceiving cicuit, Z = ω Z is the eflected impedance, is the mutual inductance of tansmitting coil and eceiving coil. Take P model as a example to analyze, the impedances in equation ( can be obtained as equation (3 Z = jω jω (3 Z = jω jω When design the magnetically couple esonant WPT system, most designes chose the inductances ==, compensating capacitances ==, and the angula fequency of diving souce is ω =. Indeed, the magnetically couple esonant WPT system is not in the magnetically coupled esonant situation, because Im(Z and Im(Zei, which means both tansmitting cicuit and eceiving cicuit ae not in the esonant situation, whee Zei=j/j( / epesents the equivalent impedance of tansmitting cicuit. In othe wods, anothe way should be taken to design the inductance o compensating capacitances to make the WPT system in a magnetically coupled esonant situation athe than just choose == and == simply. On the basis of the afoementioned analysis, a solution is poposed to solve this poblem, and the pocessing pocedue is as follows: ( the stuctues and paametes of tansmitting coil and eceiving coil ae totally the same, which means = = ; ( the compensating capacitance of eceiving coil is fixed, while that of tansmitting coil is adjustable; (3 the angula fequency of the system can be detemined to ensue the esonant of eceiving cicuit; (4 accoding to the esonant angula fequency, the compensating capacitance can be detemined. Afte the above pocessing, it can be ensued that the WPT system tansfes powe wielessly in a magnetically coupled esonant situation. onsideing the condition of P model, fo the pupose of making Im(Z=, the esonant angula fequency should be ( ( ω =, so the angula fequency of diving souce is the same as esonant angula fequency, and Z = ( is pue esistive at this esonant angula fequency point. To make

3 ( ei = Z j j is also pue esistive, the compensating capacitance can be obtained as fomula (4 = = (4 o as == and the compensating capacitance of eceiving coil is fixed, and the angula fequency of diving souce is ( ( ω =, and the compensating capacitance of tansmitting coil is ( =, the WPT system is magnetically coupled esonant, and the tansfe powe and efficiency is deduced as equation (5 ( Pout = U ( (5 ( η = ( It is the same analysis method fo model, and the compensating capacitance fo model is =, the tansfe powe and efficiency is deduced as equation (6 Pout = U η = As depicted in Fig. 3 (c and (d, accoding to Kichhoff s voltage law, mathematical equation of the models can be established as equation (7 U = ZI jω I I I = I I (7 I = ZI jω I jω = jω II Z Whee Z is the inductive eactance of the tansmitting cicuit, and Z is the impedance of the eceiving cicuit, is the mutual inductance of tansmitting coil and eceiving coil. As fo P model, the specific numeical value of Z and Z ae as follows in equation (8 Z = jω Z (8 = jω jω (6 And the specific numeical value of Z and Z fo PP model ae as follows in equation (9 Z = jω (9 Z = jω jω ω ω Accoding to the same analysis method with P model peviously, which aims to make the tansmitting cicuit and eceiving cicuit be pue esistive, the tansfe powe and efficiency fo P model and PP model ae deduced as equation ( and (, while the compensating capacitances fo P model and PP model and the esonant angula fequency ae obtained in Table I. Pout = U ( η = Pout = U ω ( η = ( ( ( ω (. aintaining the Integity of the pecifications Based on the afoementioned analysis and deivations, the tansfe powes and efficiencies fo the fou models ae obtained. Futhe analysis, when the compensating capacitances of tansmitting coils and esonant angula fequency fo each model ae detemined as Table Ithe WPT system can tansfe powe in the magnetically coupled esonant situation. eanwhile, accoding to the tansfe powes and efficiencies, the fou models can be equivalent to the unified cicuit as illustated in Fig. 4. U Z Z Figue 4. The unified equivalent cicuit of fou models Fig. 4 eveals that the tansfe powe and efficiency ae only elated to impedance Z and eflected impedance Z, afte all the othe paametes ae detemined. As fo the condition when the tansmitting cicuit is model, the impedance Z is equal to the souce intenal esistance, while as the tansmitting cicuit is P model, the impedance

4 Z is equal to j l. The Table II shows the eflected impedance Z, impedance Z, tansfe powe and efficiency fo each model as the compensating capacitances fo tansmitting coils and esonant angula fequency ae detemined as Table I TABE I. OPENATING APAITANE FO TANITTING OI AND EONANT ANGUA FEQUENY FO FOU ODE compensating capacitances P > ( P PP ( > 5 ( - esonant angula fequency ω TABE II. THE EFETED IPEDANE, TANFE POWE AND EFFIIENY FO FOU ODE eflected impedance Z ω P ( P Impedance Z ω jω Tansfe powe P out Z U Z Z ( Tansfe efficiencyη Z Z Z Z Z U Z Z Z Z It is known that the mutual inductance of two coils of which thei distance is D can be appoximately expessed as = 4 N /D 3 as in [], in which is pemeability of vacuum, is the adius of the coils, N is the numbe of tuns, D is the distance of two coils which ae coaxial. In othe wods, if the size and paamete of the coils ae fixed, a lage D means a smalle mutual inductance. Tansfe Powe/P(p.u The compaison of tansfe powes vesus mutual inductance fo fou models PP model P model P model model utual Inductance/(H Figue 5. The compaison of tansfe powes vesus mutual inductance fo fou models Tansfe Efficiency/ (% % 9% 8% 7% 6% 5% 4% 3% % % The compaison of tansfe efficiencies vesus mutual inductance fo fou models PP model P model P model model utual Inductance/(H Figue 6. The compaison of tansfe efficiencies vesus mutual inductance fo fou models In ode to make a compaison fo these fou models in tems of the tansfe powe and efficiency, the diving souce and souce intenal esistance, load, inductance coils of tansmitting teminal and eceiving teminal and compensating capacitance of eceiving teminal ae all the same. The compaison of tansfe powes and efficiencies vesus mutual inductance of coils ae depicted in Fig. 5 and Fig. 6, espectively. As shown in Fig. 5 and Fig. 6, thee can be seen that when the mutual inductance is elatively small, which means the tansmitting teminal and eceiving teminal is elatively fa apat, the tansfe powe and efficiency of PP model is the best. Namely, the PP model is the optimal stuctue in the fou topology models fo a magnetically coupled esonant WPT system since its best pefomance of tansfe powe and efficiency. And this will bing a geat help fo designes to design an efficient wieless powe tansfe system. III. IUATION EUT Fo a futhe demonstation fo the conclusion that the PP model is the optimal stuctue fo a elatively fa distance WPT system fo its best pefomance of tansfe powe and efficiency in the fou models, the softwae PPIE is used to conduct a simulation expeiment. In ode to ensue the eliability and availability of the simulation expeiment, all the paametes used in the simulation expeiment ae come fom efeences as in [] and []: = =9.6H, =.8F, =5, =5. Based on the analysis peviously, the futhe of the two coils the smalle of the mutual inductance. And coupling coefficient k is popotional to mutual inductance since = k, that means a smalle coupling coefficient k epesents a futhe tansfe distance. Futhe analysis, it can be known that the best inteval fo selecting coupling coefficient k is ~.. The simulation esults fo k=.75, which pesent the compaison of tansfe powes and efficiencies fo fou models, is elucidated Fig. 7 and Fig. 8. Fig. 7 eveals that PP model tansfe much moe powe than the othe models, and Fig. 8 illustates that PP model tansfe powe with the highest efficiency among the fou models. It is obviously that PP model is the best choice fo designing a esonant WPT system since its optimal 3

5 pefomance of tansfe powe and efficiency. And this accod with the peceding analysis esults. 5.W.5W W.W.W W 5.W.5W W W(4 W( W(6 P model model P model W PP model W E>> W KHz 3KHz KHz 3KHz 75KHz W(8 Fequency Figue 7. The simulation esults of tansfe powes fo fou models m 5m 4.m.m 7.5m 5.m.5m 5m W(4 / W(V3 W( / W(V W(6 / W(V4 P model model P model PP model E>> KHz 3KHz KHz 3KHz 75KHz W(8 / W(V5 Fequency Figue 8. The simulation esults of tansfe efficiencies fo fou models IV. ONUION Based on the cicuit theoy, this pape conducts eseach fo the fou typology models of the magnetically coupled esonant WPT system, and method of selecting the compensating capacitances fo pimay tansmitting coil is deduced, futhe analysis and compaison of the tansfe powes and efficiencies fo the fo typology models wee discussed, and the simulation is taken, too. The following conclusion will be geat helpful and instuctional fo designes to design a magnetically coupled esonant WPT system: If the tansmitting inductance coil and eceiving inductance coil ae totally the same as well as thei compensating capacitances, the WPT is not a magnetically coupled esonant system, because the elationship between the tansmitting and the eceiving teminal is not esonance. When the tansfe distance is elatively fa apat, the usage of the PP model can bing an optimal tansfe powe and efficiency fo a magnetically coupled esonant WPT system. AKNOWEDGENT This wok was suppoted by the National Natual cience Foundation of hina (6739, 64334, the Natual cience Foundation of iaoning (337 and the Pogam fo New entuy Excellent Talents in Univesity, hina (NET--6, the Fundamental eseach Funds fo the ental Univesities (N3544. EFEENE [] Tesla N. Appaatus fo tansmitting electical enegy.:, U973 A[P]. 94. [] Hoang H, ee, Kim Y, et al. An adaptive technique to impove wieless powe tansfe fo consume electonics[j]. IEEE Tansactions on onsume Electonics, vol. 58(, pp , [3] Zhang F, iu X, Hackwoth A, et al. Wieless enegy delivey and data communication fo biomedical sensos and implantable devices[]// Bioengineeing onfeence, 9 IEEE 35th Annual Notheast. IEEE, 9:-. [4] iu X, Wang G. A Novel Wieless Powe Tansfe ystem with Double Intemediate esonant oils [J]. IEEE Tansactions on Industial Electonics, vol. 63(4, pp. -, 5. [5] i, iqi, et al. "Wieless Powe Tansfe by Electic Field esonance and Its Application in Dynamic haging." IEEE Tansactions on Industial Electonics vol. 63(, pp , 6. [6] He T. Expeiment of pace ase Enegy Tansmission and onvesion with High Efficiency [J]. hinese Jounal of ases, vol. 4(3, pp. 47-5, 3 [7] Fan X, o X, Zhang X. eseach status and application of wieless powe tansmission technology [J]. Poceedings of the hinese ociety of Electical Engineeing, vol 35(, pp , 5 [8] Zhang Xian, Yang Qingxin, hen Haiyan, et al. odeling and Design and Expeimental Veification of ontactless Powe Tansmission ystems via Electomagnetic esonant oupling[j] Poceedings of the EE, vol. (, pp , [9] allan J, Villa J, lombat A, et al. Optimal Design of IPT ystems Applied to Electic Vehicle Battey hage[j]. IEEE Tansactions on Industial Electonics, vol. 56(6, pp. 4-49, 9. [] Zhen N, asanova J J, aie P H, et al. ethod of oad/fault Detection fo oosely oupled Plana Wieless Powe Tansfe ystem With Powe Delivey Tacking[J]. Industial Electonics IEEE Tansactions on, vol. 57(4, pp ,. [] AndéKus, Kaalis A, offatt, et al. Wieless Powe Tansfe via tongly oupled agnetic esonances [J]. cience, vol. 37(5834, pp , 7 [] heng, hen X, Wang J, et al. Key technologies and applications of wieless powe tansmission [J]. Tansactions of hina Electotechnical ociety, vol. 3(9, pp 68-84,5. [3] Hui Y, Zhong W, ee K. A itical eview of ecent Pogess in id-ange Wieless Powe Tansfe [J]. IEEE Tansactions on Powe Electonics, vol. 9(9, pp , 3. [4] Qiang H, Huang X, Tan, et al. tudy on Topology Design of Wieless Powe Tansfe fo Electic Vehicle Based on agnetic esonance oupling[j]. Advanced ateials eseach, vol. 38-3, pp. -3, [5] Huang X, ao W, Zhou Y, et al. ompaative study on the two kinds of models in the technology of magnetic coupling esonance system [J]. Tansactions of hina Electotechnical ociety, vol. s, pp. 3-7,

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