Experiment of Magnetic Resonant Coupling ThreeThree----phasephase Wireless Power Transfer Yusuke Tanikawa, Masaki Kato, Takehiro Imura, Yoichi Hori Organized by Hosted by In collaboration with Supported by 2/26 What is our research? Organized by Hosted by In collaboration with Supported by 3/26 Contents 0. What is our study? : Movie 1. Background of Wireless Power Transfer 1.1. General information of WPT 1.2. Why three phase? 2. Approach of our study 2.1. General info. & parameters 2.2. Theoretical formula 2.3. Experiment and result 3. Conclusion and future works Organized by Hosted by In collaboration with Supported by 4/26 Contents 0. What is our study? : Movie 1. Background of Wireless Power Transfer 1.1. General information of WPT 1.2. Why three phase? 2. Approach of our study 2.1. General info. & parameters 2.2. Theoretical formula 2.3. Experiment and result 3. Conclusion and future works Organized by Hosted by In collaboration with Supported by 5/26 1.1. General info. for WPT 1/3 Wireless Power Transfer (WPT) Applications: EV , mobile, and battery charger Conventional WPT: Single phase AC transfer Organized by Hosted by In collaboration with Supported by 6/26 1.1. General info. for WPT 2/3 Three methods of WPT technologies Magnetic Magnetic Resonant Methods Microwave Induction Coupling Images Transfer Gap Up to 0.2 m Up to 10 m A few hundred km Efficiency Up to 95% Up to 97% Up to 60 % Robustness for Poor Great Good Displacement Organized by Hosted by In collaboration with Supported by 6/26 7/26 1.1. General info. for WPT 3/3 Magnetic Resonant Coupling • Transmitter and receiver: LC resonators • High efficiency (around 90%) at 1 m gap • Transfer frequency: 100 kHz to 20 MHz – Power devices for kHz switching • Relay resonators (single phase) – Suitable for charging EVs while running Organized by Hosted by In collaboration with Supported by 8/26 1.2. Why three phase? 1/3 1. Advantage for high power transfer 2. Suitable characteristics for WPT a a' ~~~ Z N N' Z + ~~~ ~~~ c+ b c' Z b' Organized by Hosted by In collaboration with Supported by 9/26 1.2. Why three phase? 2/3 Advantages for high power transfer • Larger power capacity with same devices – Capacity limit: three times of single phase (High frequency devices: Low power limit) • Relatively simple system Single phase Three phase Power limit ratio 1 3 Device quantity 2 (4 switches, 2 lines) 3 (6 switches, 3 lines) Circuits Organized by Hosted by In collaboration with Supported by 10/26 1.2. Why three phase? 3/3 Suitable characteristics for WPT • Smaller ripples of rectified DC ACU相 (U) V相AC (V) 2 2 ACW相 (W) DC整流波形 整流前波形 1.5 AC DC整流波形 1.5 1 1 0.5 0.5 ×Vo 0 ×Vo 0 0 60 120 180 240 300 360 -0.5 -0.5 0 60 120 180 240 300 360 -1 -1 -1.5 -1.5 位相角[°] 位相角[°] Single phase Three図 三相交流の全波整流 phase 単相交流の整流電圧 • Rotation symmetry: contact-less terminal Conventional method Photo ：Wikipedia Photo ：Toyonaka industry WEB Organized by Hosted by In collaboration with Supported by 11/26 Contents 0. What is our study? : Movie 1. Background of Wireless Power Transfer 1.1. General information of WPT 1.2. Why three phase? 2. Approach of our study 2.1. General information & parameters 2.2. Theoretical formula 2.3. Experiment and result 3. Conclusion and future works Organized by Hosted by In collaboration with Supported by 12/26 2.1. General info. & parameters 1/2 Experiment & analysis of ThreeThree----phasephase WPT 1. Comparison of data and theoretical formula 2. Rotation experiment: collection of measured values • Each 15 degree from 0 to 360 degree • Mutual inductance between resonators • Ratio of voltage (V), current (I), and power (P) Mutual inductance Ratio between transmitter and receiver Formula (Measured value) (Calculated value) Transmitter V, I, and P Comparison (Measured value) Ratio between transmitter and receiver Receiver V, I, and P (Measured value) (Measured value) Organized by Hosted by In collaboration with Supported by 13/26 2.1. General info. & parameters 2/2 Voltage ratio I2 V Receiver2nd side side 2 V2 Av = V1 I1 Current ratio Lm V1 st ~~~ 1Transmitterside side I 2 ~~~ ~~~ Ai = I1 Coupling coefficient Efficiency (Power ratio) (nondimensionalized mutual inductance) P V ⋅ I L L L η = out = 2 2 = A ⋅ A k = m = m = m v i Pin V1 ⋅ I1 L1 L2 880 µH Power factor = 1.0 (resonant condition) Organized by Hosted by In collaboration with Supported by 14/26 2.2. Theoretical formula 1/3 Base theoretical formula of single phase Resonance: simple formula of mutual inductance andLm load resistance RL ω0 = L1C1 = L2C2 At experiment; RL=50 ohm Voltage ratio V2 ω0 Lm RL Av = = j 2 = Av (Lm , RL ) V1 R1RL + R1R2 + (ω0 Lm ) Current ratio I 2 ω0 Lm Ai = = j = Ai (Lm , RL ) I1 (RL + R2 ) Efficiency (Power ratio) (ω L )2 R η = A ⋅ A = 0 m L Masaki Kato, Takehiro Imura, Yoichi Hori, “The Characteristics when Changing Transmission Distance v i 2 and Load Value in Wireless Power Transfer via Magnetic Resonance Coupling”, (RL + R2 ){R1RL + R1R2 + (ω0 Lm ) } The 34th International Telecommunications Energy Conference (INTELEC 34th), 2012 Organized by Hosted by In collaboration with Supported by 15/26 2.2. Theoretical formula 2/3 Modification of formula to three phase • Three phase; a lot of mutual inductance values To adapt the single phase formula; how to combine the values into one value ? • Combination of trigonometric function ~ π 2π Phase difference L = L sin( ω t ) + L sin( ω t + ) + L sin( ω t + ) m m 1 m 2 3 m 3 3 2 2 2 = ( L m 1 + L m 2 + L m 3 ) − ( L m 1 L m 2 + L m 2 L m 3 + L m 3 L m 1 ) sin( ω t + φ ) I2 Combined Lm V Receiver2nd side side 2 ( )2/3 L − ( )2/3 L sin φ = m2 m3 2 2 2 (Lm1 + Lm2 + Lm ) − (Lm1Lm2 + Lm2 Lm3 + Lm3Lm1) I1 3 Lm V1 L − (L )2/ − (L )2/ ~~~ Transmitter1st side side cosφ = m1 m2 m3 ~~~ ~~~ 2 2 2 (Lm1 + Lm2 + Lm3 ) − (Lm1Lm2 + Lm 2 Lm3 + Lm3Lm1) Organized by Hosted by In collaboration with Supported by 16/26 2.2. Theoretical formula 3/3 Optimal load for efficient maximization • Efficient formula: function of load resistance 2 ω0 (Lm RL ) η = Av ⋅ Ai = 2 (RL + R2 ){R1RL + R1R2 + (ω0 Lm ) } • Optimal value of load resistance 2 R2 2 RL = R2 + (ω0 Lm ) R1 Organized by Hosted by In collaboration with Supported by 17/26 2.3. Experiment 1/7 (Setting) • Resonant frequency: 120 kHz • Cable: Y connection – Rotation symmetry – 50 ohm load resistance • Resonators Phase a Phase b Phase c Self inductance ［μH ］ 8.73 ×10 2 8.68 ×10 2 8.69 ×10 2 Cable: 2 mm 2 Internal resistance ［Ω］ 1.21 1.23 1.12 Diameter: 1.7 mm Resonant capacitance ［pF ］ 2.04 ×10 3 2.09 ×10 3 2.04 ×10 3 Pitch of coil: 2.5 mm Quality factor 5.46 ×10 2 5.36 ×10 2 5.89 ×10 2 Resonant frequency ［kHz ］ 1.19 ×10 2 1.19 ×10 2 1.20 ×10 2 Capacitor: 2000 pF Self inductance ［μH ］ 8.67 ×10 2 8.69 ×10 2 8.69 ×10 2 Internal resistance ［Ω］ 1.17 1.23 1.20 Resonant capacitance ［pF ］ 2.07 ×10 3 2.03 ×10 3 2.04 ×10 3 Quality factor 5.63 ×10 2 5.36 ×10 2 5.49 ×10 2 Receiver Transmitter Resonant frequency ［kHz ］ 1.19 ×10 2 1.20 ×10 2 1.20 ×10 2 Organized by Hosted by In collaboration with Supported by 18/26 2.3. Experiment 2/7 (Result 1/6) Mutual inductance Lm (Coupling coefficient k) 120 60 A-A Combined mutual inductance; B-A calculated from measured values C-A L L L k = m = m = m 0 [deg] 180 0.00 0.10 0.20 L1 L2 880 µH Lkm 240 300 Close position: small rotation angle Strong coupling Organized by Hosted by In collaboration with Supported by 19/26 2.3. Experiment 3/7 (Result 2/6) Optimal load resistance Z L 120 60 最適負荷Optimal value Similar shape to mutual inductance 0 [deg] 180 60 120 180 [Ω] RL 2 R2 2 RL = R2 + (ω0 Lm ) R1 240 300 Organized by Hosted by In collaboration with Supported by 20/26 2.3. Experiment 4/7 (Result 3/6) Phase difference φof voltage A-A 0-45 degree; phase = -90 degree 120 60 B-A 60 degree; phase = 180 degree C-A 75-120degree; phase = 150degree A-A Cal =－120 －90 ＋360 degree B-A Cal C-A Cal Precise shape Between calculation and 0 [deg] 180 30 150 270 measured value [deg] ( )2/3 A − ( )2/3 L sin φ = 2 3 2 2 2 (L1 + L2 + L3 ) − (L1L2 + L2 L3 + L3L1) L − (L )2/ − (L )2/ cosφ = 1 2 3 2 2 2 240 300 (L1 + L2 + L3 ) − (L1L2 + L2 L3 + L3L1 ) Organized by Hosted by In collaboration with Supported by 21/26 2.3. Experiment 5/7 (Result 4/6) Voltage ratio Av ω0 Lm RL Av = j 2 R1RL + R1R2 + (ω0 Lm ) At 60 degree, Voltage ratio is maximum . Calculated value < Measured value At optimal load; circular shape Organized by Hosted by In collaboration with Supported by 22/26 2.3. Experiment 6/7 (Result 5/6) Current ratio Ai 50[Ω] 負荷 計算値 50[Ω] 負荷 実測値 最適負荷 計算値 ω0 Lm Ai = j (RL + R2 ) At 60 degree, Current ratio is minimum.