Report

High Efficiency Wireless Charging of Electric Vehicles for Safe and Economic Future Transportation Chris Mi, Ph.D, Fellow IEEE Professor, Department of Electrical and Computer Engineering Director, DOE GATE Center for Electric Drive Transportation University of Michigan-Dearborn, (313)583-6434; [email protected] Conventional EV Charging 1 2 3 Normal charging Fast charging Battery swapping AC charging using level 1 or level 2， voltage at 110V, 220V， 6-10 hours per charge Mostly DC charging in 15 to 30 minutes. Investment of battery packs; standardization is difficult; swapping stations need a lot investment, space and manpower; safety and reliability is of concern Charge at home or public space, need large installation of charge stations For an EV with a 24kWh battery pack, charging in 15 minutes means 96kW. This is way over the power available in private homes. Issues of Con. Charging and Battery Swapping Electric safety is of concern: electric shock due to rain, etc. Charge station, plug and cable can be easily damaged, stolen Charge/swap station takes a lot of space and affect the views Wireless Charging Definition of WPT Wireless power transfer (WPT) Inductive power transfer (IPT) Contactless power system (CPS), Wireless energy transfer Strongly coupled magnetic resonance High-efficiency inductive-power distribution The essential principles are the same given the distances over which the power is coupled is almost always within one quarter of a wavelength and therefore, the fundamental operation of all of these systems can be described by simple coupled models Grant Covic and John Boys, “Modern Trends in Inductive Power Transfer for Transportation Applications,” IEEE journal of emerging and selected topics in power electronics, vol. 1, no. 1, march 2013 Methods of Wireless Power Transfer Electromagnetic Induction Radio wave 电磁感应式 无线电波 Wireless Power Transfer Radiation Microwave 电能的无线传输 辐射式 微波 Electromagnetic Resonance Laser 电磁谐振式 激光 In 1830’s, Faraday's law of induction In 1890’s, Tesla had a dream to send energy wirelessly GM EV1 used an Inductive charger in the 1990’s 2007, MIT demonstrated a system that can transfer 60W of power over 2 m distance at very low efficiency Wireless/inductive chargers are available on the market Qualcomm, Delphi (Witricity), Plugless Power, KAIST, etc. have developed EV wireless charger prototypes Ultrasound 超声波 Predicted Wireless Charging Market $17 Billion in 2019 Problems and Difficulties Magnetic field is diminishing proportional to1/r3 Often the mutual inductance is less than 20% or 10% of the self inductance Analytical calculation of coil mutual inductance is next to impossible Further analytical method is needed Numerical simulation and coupled field - lumped parameter simulation is also of paramount importance High frequency HFSS instead of static FEM for high frequency High cost Low efficiency Large size Limited distance Sensitive to vehicle alignment Need novel designs and methods to study these systems A Wireless Power Transfer System Secondary controlled WPT Covic, G.A.; Boys, J.T., "Inductive Power Transfer," Proceedings of the IEEE , vol.101, no.6, pp.1276,1289, June 2013. Equivalent Circuit Series-Series L1, L2 – Self inductance Series-Series Resonance Structure Lm – Mutual inductance L1= L1σ +Lm; L2= L2σ +Lm 1 R j ( L ) j L 1 1 m I C V 1 1 1 0 1 I2 j Lm RL R2 j ( L2 ) C2 Power Transferred Power of output side 2 2 V ( L ) RL 2 1 m P2 | I 2 | RL 2 2 | [ Z1Z 2 ( Lm ) ] | 1 0.9 0.8 0.7 0.6 0.5 Calculated 0.4 0.3 Power of the input side efficiency 0.2 0.1 0 0 1 2 3 4 5 6 7 V12 | Z 2 | P1 | V1 | | I1 | cos cos 2 | Z1Z 2 ( Lm ) | Efficiency P2 ( Lm )2 RL P1 | Z 2 [ Z1Z 2 ( Lm ) 2 ] | cos 8 9 10 System Topology at UMD Key inventions: - Optimized multi-coil design for maximum coupling, with bipolar architecture LCC topology for soft switching to further increase efficiency and frequency Distributed circuit parameters to minimize the capacitor size and voltage rating Bidirectional LCL Power factor correction circuit to maximize the front end efficiency and reduce system cost Foreign object detection and electromagnetic field emissions for human and animal safety for the developed system. Double-sided LCC Compensated Wireless Power Transfer Topology S1 S3 iLf1 Vin Lf1 + Cf1 + - B S2 M + A S4 iLf2 C1 i1 + L1 • • Lo D3 + + L2 C2 + Lf2 i2 Vout CO Cf2 Sending Side • D1 D2 Battery Pack D4 Receiving Side Important Characteristic: The output current at resonant frequency: The output power can be expressed as: I Lf 2 I Lf 2 _1 Um L k U1 0 L f 0 L2f P U 2 I Lf 2 _1 L k U1 U 2 0 L2f 11 Comparison of Coil Design (a) Circular pads, (b) flux-pipe pads (c) DD-DDQ bipolar pads Trong-Duy Nguyen, Siqi Li, Weihan Li, Chunting Chris Mi, Feasibility Study on Bipolar Pads for Efficient Wireless Power Chargers, IEEE Applied Power Electronics Conference, Fort Worth, TX, USA, March16-20, 2014 Typical Misalignment Door-to-door (right-left)is more difficult Front-rear is easier to align Z (height) Rectangular bipolar pads Rectangular Unipolar pads Five Studied Cases Case 1: 480x1000 Case 2: 600x800 Case 3: 693x693 Case 4: 800x600 Case 5: 1000x480 771.4 x 16 x 16 600 x 16 x 16 589.1 x 16 x 16 415.4 x 16 x 16 360 x 16 x 16 925.7 x 16 x 16 720 x 16 x 16 589.1 x 16 x 16 498.5 x 16 x 16 432 x 16 x 16 7 9 11 13 15 480 x 1000 x 6 600 x 800 x 6 693 x 693 x 6 600 x 800 x 6 1000 x 480 x 6 Receiver 480 x 1000 x 8 600 x 800 x 8 693 x 693 x 8 600 x 800 x 8 1000 x 480 x 8 Sender Ferrite bar dimension ( L x W x H *) Receiver Number of ferrite bars Sender Coil Z (height) Coils: Similar area Ferrites: Similar volume X & Y Misalignment Kx (door-to-door misallignment) Ky (front-to-rear misallignment) 1_1_S2R2_X600xY800_noShield_dx 0.35 1_2_S2R2_X600xY800_noShield_dy 0.35 Curve Info Curve Info Ky_600x800 Kx_480x1000 0.30 0.30 Ky_693x693 Kx_600x800 Ky_800x600 Kx_693x693 0.25 Ky_480x1000 Kx_800x600 0.25 Ky_1000x480 Kx_1000x480 Coupling Coupling 0.20 0.20 0.15 0.15 0.10 0.05 0.10 0.00 0.05 -0.05 0.00 0.00 100.00 200.00 300.00 400.00 500.00 x_misalligned [mm] 600.00 700.00 800.00 1. The maximum coupling coefficient decreases with the increase of coil’s X-length 0.00 100.00 200.00 y_misalligned [mm] 300.00 The topology with bigger Y-size has a better Y-misalignment tolerance Z (height) 2. X-misalignment tolerance increases with the coil’s X-length -0.10 400.00 Angular Misalignment Typically, when a driver parks an EV, the worst angular misalignment can be limited at about 30° Coupling coefficient vs x, y, theta Z Finite element analysis using Maxwell 3D Y X Coupling Coefficient Profile versus Door-to-door and Front-to-rear Misalignments Safety issues Range of flux density is within 1-1.2 meters, with chassis - perfectly aligned position => It is safe to install this WPC in an electric vehicle chassis, typically about 1.8meter doorto-door size With chassis - maximum misaligned position Exposed field to a human of 1.8-meter high Human body is exposed to maximum about 1.6uTesla in foot area while about 0.06uT in head area. Field exposed to a man of 1.8met height 1.60 Curve Info 1.40 Time='13250ns' Time='13500ns' Time='13750ns' 1.20 Time='14000ns' Time='14250ns' 1.00 Mag_B [uTesla] Time='14500ns' Time='14750ns' 0.80 Time='15000ns' Time='15250ns' Time='15500ns' 0.60 Time='15750ns' Time='16000ns' 0.40 Time='16250ns' 0.20 0.00 0.00 0.25 0.50 0.75 1.00 Distance [meter] 1.25 1.50 Human’s height [in meter] 1.75 2.00 Experimental Verification Output current Input current Output voltage Input voltage Max power: 8kW Max Eff.: 97% 21 Experiment Results Xmis=0mm, Gap =200mm Xmis=300mm, Gap =200mm Xmis=125mm, Gap =400mm (Rectifier + PFC) + Buck + Wireless PFC – power factor correction >0.98 Buck for charge control WPT: fixed frequency, auto-tuned system. WPT System Efficiency for Different Vbat Dynamic In-Motion Charging Buried tracks Results of Foreign Object Test #1 Experiment Result: the gum wrapper was burned and there left an imprint, which means the temperature is high. Conclusions Misalignment tolerance was analyzed and discussed Two kinds of coupling coefficient detection methods were proposed 8 kW wireless charger prototype with 200mm gap and 300mm door-to-door misalignment tolerance had been built and tested Coupling coefficient maintains at 18.8%~31.1% With a 200mm gap, 95.66% efficiency (at about 8kW) from DC to DC was obtained at desired position 95.39% efficiency (at about 4kW) at 300mm Xmisalignment and 200mm Gap Acknowledgement Department of Energy - GATE Program DENSO International US China Clean Energy Center GATE Industrial Partners - Chrysler, Ford, DENSO International, Mathworks, dSPACE, ANSYS, Hp Pelzer, EDTA, PSIM, GaN Systems IEEE Workshop and TPEL Special Issue on Wireless Power 2015 WoW Sponsored by six Societies of IEEE PELS, IAS, IES, VTS, MAG, PES June 5-6 (Fri.-Sat.), 2015, Daejeon, Korea Held just after the 2015 ECCE-Asia (June 1-4) in Seoul General Chairs: Dr. Chun Rim, Dr. Chris Mi TPC: Dr. John Miller http://www.2015wow.org IEEE Transactions on Power Electronics (Guest-EIC) IEEE Journal on Emerging and Selected Topics on Power Electronics (Guest-EIC)