论文206110608 黄鑫design and study of wireless po

1、Design and study of multi-dimensional wireless power transfer systems and architecturesJohnson I. Agbinya , Nagi F. Ali MohamedDepartment of Electronic Engineering, La Trobe University, Bundoora, Victoria 3083, Australiatransmissiona r t i c l ei n f oThis paper reports on the design of multidimensi

2、onal wireless power distribution using cellular concept, Helmholtz coils and cubical node design with power transmission capability over a distance of 6 m. To provide strong and uniform power delivery along the power transfer link axis, pairs of Helmholtz coils which are capable of creating uniform

3、magnetic fields are used. To distribute wireless power in multiple dimensions the transmitter containing six secondary coils and one primary coil were used. The secondary coils orient magnetic files in six directions and the primary coil provides power transfer in the vertical direction. A cellular

4、concept which permits the planning of power transfer over wide area is proposed. Furthermore, we have used a class E power source to power the transmitter. Class E power amplifiers provide stable resonant outputs to which the transmitter responds in sympathy. They also provide high voltage outputs a

5、nd low currents making them safe for high voltage operations. The proposed cellular architecture with the multidimensional transmitter and receivers are demonstrated to be an excellent choice for inductive wireless power distribution over long distances. The multidimensional transmitter behaves like

6、 an inductive power coupler. With only one multidimensional transmitter and receivers, a range of about 6 m has been achieved end to end. The cellular architecture allows the power transfer network to be planned. Further range extension can be achieved by using a relay coil placed 9 cm above the pri

7、mary coil.2014 Elsevier Ltd. All rights reserved.Article history:Received 28 August 2013Received in revised form 19 June 2014 Accepted 23 June 2014 Availableonline 30 July 2014Keywords:Wireless power transferPower system Multi-dimensional wireless power transmission systems Inductive methodsMIMOa b

8、s t r a c tIntroductionsystems. In most cases trial and error methods are used to ascertain the best locations for the transceivers. Poor placing of the coils leads to not only crosstalk but also frequency splitting so that maximum power is not transferred at the required resonant frequency.Historic

9、ally, Nikola Tesla in 1927 conjectured with experiments the possibility of broadcasting wireless energy round the globe 1. Nikola demonstrated that both radio waves and inductive methods can be used. The telecommunications field is also awash with different forms of wireless broadcasting of electrom

10、agnetic waves including long waves, short waves, ultra high frequency (UHF) radio, television (TV), mobile communications (GSM, GPRS, UMTS, PCS and 4G) to wireless local area networks (WLAN) to mention a few. These forms of RF broadcasting are all used for transferring of data in electromagnetic for

11、ms but rare for transport of electrical power for lighting houses and equipments. In the real sense they may be used for that purpose but the commercial intentions have never been for that and hence the modern re-discovery of wireless energy transfer may be termed a new paradigm for harvesting, gene

12、ration, transmission and distribution of electrical energy.Transmission lines have historically been used for distribution of electric power over long distances and wide area. However unlike normal electric power transmission, the application of transmission lines are not suited for inductive wirele

13、ss power distribution since doing so negates the very essence of wireless power transfer. Hence new paradigms are required for wireless power transmission and distribution over wide areas and long distances. In this paper a cellular concept similar to cell planning in mobile communication is propose

14、d. Cellular power sources can result in wide area wireless power distribution provided issues dealing with crosstalk and rapid decay of inductive power are tackled. A great deal of effort is required to reduce crosstalk between neighbouring coils in inductive systems. At the moment, this problem rem

15、ains unsolved and all resonant systems are susceptible to crosstalk of some sorts. Hence establishing the optimum locations of resonant coils to enhance power transfer remains an area of research interest in wireless power transfer and inductive communicationCorresponding author.E-mail address: j.ag

16、.au (J.I. Agbinya)./10.1016/j.ijepes.2014.06.071 0142-0615/ 2014 Elsevier Ltd. All rights reserved.1048J.I. Agbinya, Nagi F. Ali Mohamed/ Electrical Power and Energy Systems 63 (2014) 1047 1056While a great deal of effort has been dedicated to demonstrating wireless p

17、ower transfer over tens of centimetres, there remains the need for demonstrating distribution of wireless power transferDoppler frequency shifts and large system bandwidth. Resonance methods need not use large bandwidth systems and velocities can be determined based on the coupling coefficients in t

18、he system. Recently anti-collision systems using RFIDs have been studied 1012 but suffer from co-channel interference and hence inability to identify tags. Collisions from multiple tags responding to beacon transmissions limit performance. To reduce this problem elaborate medium access techniques we

19、re developed by several authors 1012. However, in a busy highway, multiple collisions will limit the determination of accurate positions and speeds of interfering vehicles 68.Wireless power transmissions with two coils over distances of more than 1 m are rare. Normally to increase the transmission r

20、ange three to four resonant coils are used as in 1720. This paper introduces a new design based on a cubical structure which permits simultaneous power distribution in many directions and over very large distances of up to 6 m. Only two coils are involved in power transmission along a given axis.The

21、 rest of the paper follows the following format. In section Wide area energy transfer architecture we propose a new design framework for distributing inductive wireless power into many directions with enhanced range. A cellular architectural framework is presented for multiple input and multiple out

22、put configurations. Experiments are conducted and measurements of the induced voltages are given over a spherical surface centred on the transmitter. In section Hardware implementation, implementation of multidimensional flux design and distribution system networks is given. Section Cellular wide ar

23、ea wireless power distribution develops the proposed cellular wireless power distribution network. In this section we also design and implement a class E input power source. Section Experiments and results describes a series of validation experiments based on our hardware design. The application sec

24、tion, describes areas where the multi-dimensional WPT system may be used. Conclusions are drawn in section Conclusions.(WPT) in many directions, to large distances and over only desirable locations. Some of the concepts required for achieving these expanded scope of WPT have been used in one form or

25、 the other in electric motors, generators and synchronous machines worldwide, in turbines and for generation of the traditional 50 Hz (60 Hz) electric power to homes and industries. Interestingly as more and more new applications of inductive wireless power transfer emerges, it is clear that some ap

26、plications require focused and directed magnetic fields into desired directions, with preferred gradients and of preferred beamwidth. Several essential requirements need to be met. Four of such requirements for resonant wide area WPT systems are the following. Firstly, both the transmitter and recei

27、ver must resonate at the same operating frequency. Secondly, power should be transferred over reasonably long distances. Thirdly, the magnetic fields need to be focused. Fourthly, the magnetic fields should be constrained to only desirable directions and for safety purposes away from other areas suc

28、h as field-free zones.Different applications require different field characteristics. For robotic propulsion and navigation 24, uniform magnetic fields are required. In autonomous navigation of micro robots 22 uniform fields with desirable gradients not only ensures directivity of the robot but also

29、 propulsion with the required optimum magnetic force. To achieve this in micro robot navigation 3, two Helmholtz coils 2,4 are used to create a uniform magnetic field between them. The uniform field orients a micro robot in a desired direction. Then two Maxwell coils carrying currents in opposing di

30、rections are used to create a propulsion magnetic force for the micro robot 24. Magnetic field coding could greatly enhance the design of such systems to ensure decoupling of the direction of propulsion from the orientation 3,4 and control 22 of micro robots and reduce crosstalk.Furthermore there is

31、 possibility for green energy using inductive energy transfer in homes. This requires the magnetic fields to be focused, be multi- dimensional and for safety reasons also provide field-free zones in homes. Furthermore, shaping of the magnetic fields by the inductive transmitters and how to plan netw

32、orks of inductive receivers could enhance the use of inductive energy transfer systems in homes and desktop wireless chargers 21. In applications such as inductive wireless powering of homes and desktop chargers, safety and health concerns make it undesirable to have induced magnetic fields everywhe

33、re. It is therefore essential to direct the magnetic field away from areas which should be free of magnetic fields. Unfortunately to date, there are no reported techniques for doing this.It has been observed that magnetic fields are not affected by multipath impairment as are electromagnetic waves.

34、Magnetic fields are also relatively immune to reflection, diffraction and the effects of their environments provided there are no magnetic materials there. These advantages make magnetic fields suited to sensing in environments where the effects of the environment could be severe with electromagneti

35、c radiation such as in anticollision systems in transportation and vehicular networks. Although the application of resonance coupling in vehicular anticollision radar systems is yet to be reported, it has the potential to outperform anti-collision systems based on linear frequency modulated continuo

36、us wave (FMCW) technologies 9. FMCW anti-collision can determine both the velocity and the proximity of a nearby vehicle usingWide area energy transfer architectureRecently we proposed flux concentrators and separators as building template for wide area wireless power transfer systems with reduced c

37、rosstalk 5. While the techniques in 5 have applications in wide area communication systems, body area networking and Internet of things architecture, they are however not able to create flux free zones and do not demonstrate how effective multidimensional focused magnetic fields could be created. A

38、multidimensional wireless power system broadcasts wireless power. It is defined as arrays of inductive power transmitters separated from each other by receivers and arranged in inductive power cells to power large geographical area. The basic building block is the binary multiple-input- single-outpu

39、t (MISO) cell shown in 5 (Fig. 1). In the binary MISO, two transmitters (TX) are used to create the required magnetic field for a receiver (Fig. 1(a). The objective of the binary MISO system is to increase the inductive power to a receiver with reduced crosstalk. By doubling the distance to (2r) bet

40、ween the transmitters in (Fig. 1(a), the crosstalk between them isJ.I. Agbinya, Nagi F. Ali Mohamed/ Electrical Power and Energy Systems 63 (2014) 104710561049reduced considerably. When used for data communication, it also leads to increased data capacity as demonstrated in 5.A binary SIMO is shown

41、in Fig. 1(b) in which one transmitter feeds two receivers placed on either side at equal distances. In this case if the receivers are identical they intercept equal amounts of inductive energy. Also the crosstalk between them is reduced considerably because the separation between them is doubled 5.I

42、n the next sections we propose how to use this binary architectural framework of Fig. 1 for creating (a) a wide area inductive wireless energy transfer system (b) for ensuring a region free of magnetic field and (c) for multi-dimensional focusing of magnetic fields. Matlab simulations and hardware e

43、valuation of the proposed systems are provided.Fig. 2. Cellular wireless power transfer architecture.(a)(b)Fig. 1. Binary MISO framework.Flux coding in wide area energy transferTo design multi-dimensional inductive wireless power transfer systems with reduced crosstalk, we propose field coding. Fiel

44、d coding is defined as the application of orthogonal matrices to orient magnetic fields to desired directions. The technique proposed can be used for extending the range of inductive power transfer systems, to focus magnetic fields and direct them in many directions. In this paper we only demonstrat

45、e and present flux coding for multidimensional flux transmission. The technique also demonstrates how to create zones of interest where field singularities (nulls) exist as essential requirements for keeping chosen areas clean and safe from magnetic fields. A field free region can be created by usin

46、g orthogonal coding of the flux created by transmitters or receivers if they share common axes as in Figs. 2 and 3. The objective in creating a region free of magnetic field is to ensure we have reduced crosstalk and a place in the power network at which we could place a transmitter (receiver) or vi

47、ce versa. Fig. 2 demonstrates this concept. Consider Fig. 4 in which we have N coils P1, P2, ., PN placed around a circular contour with each coil subtending equal angle at the centre of the circle. Assume also the coils carry currents of equal magnitudes but of different phases. Hence the magnetic

48、fields created by such coils also have different angular orientations. For the sake of illustration we will analyse a pair of the coils placed along a common axis as in Fig. 3. For any coil, the two- dimensional (2D) magnetic field vector can be written in polar form asFig. 3. Helmholtz (Maxwell) co

49、ils carrying currents in same (opposing) direction.Hk jHjejhk1where 1 6 k 6 N. In the rest of the paper let the reference point for measuring the angular spread of the coils be set to h1 and referred to coil P1. The analyses for 2, 3, 4 and N are given in the next sections. The angular orientations

50、a of the magnetic fields developed by coils with respect to each other can be defined in two dimensions in terms of the rotation matrix:Fig. 4. Multi-dimensional coil array.cosasina cosa sinaRa 2aAssume that the reference coil is located at angle h1, its neighbouring coils (left and right) on the ci

51、rcular contour are located at angles h1 a which allows the field strengths from these coils to be defined in terms of the field strength from the reference coil. Consider that the N coils are distributed uniformly around a circular frame of radius r.Hence the field components for the next coil with

52、respect to the reference coil are given by the expression:1050J.I. Agbinya, Nagi F. Ali Mohamed/ Electrical Power and Energy Systems 63 (2014) 10471056fields created by the multiple pairs of Helmholtz coils. To distinguish the coils, at the design level, one of the pairs of Helmholtz coils is consid

53、ered as reference pair with the axis oriented at angle h1 with respect to the x-axis in the horizontal plane. At the angle h1 from their common axis, the x- and y-components of the field created by a coil are given by the expressioncosasina Hx # H1x #2bsina cosaH1yHyHyx and H are the field component

54、s for the reference coil. We can show that ifthe second coil is also located at angle a from coil 1, its field components are given by the expression:Hx Hmax cosh1Hy Hmax sinh15aIn the architecture in Fig. 4 the remaining pairs are energised with currentswith specified phases. N-dimensional magnetic

55、 fields can be achieved if the currents in the pairs of coils are given by the expressions H2x #cosasina2#Hx2cIx;n Imax coshnIy;n Imax sinhn6sina cosaH2yHyHence in general the Nth coil on the circular frame has field components)a and n is an integer. For example the currents in coils P2where hn = #

56、HNxcosaand P5 with respect to the coils P1 and P4 are given by the expressionssina N Hx #HNysinacosaIx;2 Imax cosh1 aIy;2 Imax sinh1 aAlso the currents in coils P3 and P6 can be shown to be given by the expressions6aHy3In other words the orientations and locations of the field components for all the

57、 coils are known. The above results can be shown to be also true for arbitrary rotations or locations of other coils on the circular frame with respect to the reference coil. The rotation matrices are individually orthogonal. Hence the fields are coded in orthogonal manner with respect to each other

58、.Ix;6 Imax cosh1 aIy;6 Imax sinh1 aThe above framework shows that the currents in the coils can be obtained by rotating the phase defined by the reference pair. The rotations are with respect to the x-axis on the horizontal plane defined by the structure of coils. We can therefore show that the general relationships between the currents in the pairs of Helmholtz coils can be obtained with the matrix relationship6