# Combined Conformal Strongly-Coupled Magnetic Resonance for Efficient Wireless Power Transfer

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## Abstract

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## 1. Introduction

## 2. System Model of the Proposed Hybrid WPT System

## 3. Theoretical Analysis of Strongly-Coupled WPT Systems

## 4. Numerical Analysis

## 5. Experimental Setup

#### 5.1. System Design and Measurement

#### 5.2. System Maximum Efficiency

#### 5.3. Combined System Efficiency

#### 5.4. Angle Coverage

#### 5.5. The Impact of the Coils’ Misalignment

## 6. Charger Efficiency Based on the Measured Results

## 7. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

- Rabie, K.M.; Adebisi, B.; Rozman, M. Outage probability analysis of WPT systems with multiple-antenna access point. In Proceedings of the 2016 10th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP), Prague, Czech Republic, 20–22 July 2016; pp. 1–5. [Google Scholar]
- Rabie, K.M.; Adebisi, B.; Alouini, M.S. Wireless power transfer in cooperative DF relaying networks with log-normal fading. In Proceedings of the 2016 IEEE Global Communications Conference (GLOBECOM), Washington, DC, USA, 4–8 December 2016; pp. 1–6. [Google Scholar]
- Moriwaki, Y.; Imura, T.; Hori, Y. Basic study on reduction of reflected power using DC/DC converters in wireless power transfer system via magnetic resonant coupling. In Proceedings of the IEEE International Telecommunications Energy Conference, Amsterdam, The Netherlands, 9–13 October 2011; pp. 1–5. [Google Scholar]
- Li, Y.; Mai, R.; Lin, T.; Sun, H.; He, Z. A novel WPT system based on dual transmitters and dual receivers for high power applications: Analysis, design and implementation. Energies
**2017**, 10, 174. [Google Scholar] [CrossRef] - Li, Y.; Wang, Y.; Cheng, Y.; Li, X.; Xing, G. QiLoc: A Qi wireless charging based system for robust user-initiated indoor location services. In Proceedings of the IEEE International Conference on Sensing, Communication, and Networking, Seattle, WA, USA, 22–25 June 2015; pp. 480–488. [Google Scholar]
- Liu, X. Qi standard wireless power transfer technology development toward spatial freedom. IEEE Circuits Syst. Mag.
**2015**, 15, 32–39. [Google Scholar] [CrossRef] - Van Wageningen, D.; Staring, T. The QI wireless power standard. In Proceedings of the International Power Electronics and Motion Control Conference, Ohrid, Macedonia, 6–8 September 2010; pp. 15–32. [Google Scholar]
- Haldi, R.; Schenk, K.; Nam, I.; Santi, E. Finite-element-simulation-assisted optimized design of an asymmetrical high-power inductive coupler with a large air gap for EV charging. In Proceedings of the IEEE Energy Conversion Congress and Exposition, Denver, CO, USA, 15–19 September 2013; pp. 3635–3642. [Google Scholar]
- Wen, F.; Huang, X. Optimal magnetic field shielding method by metallic sheets in wireless power transfer system. Energies
**2016**, 9, 733. [Google Scholar] [CrossRef] - Haldi, R.; Schenk, K. A 3.5 kW wireless charger for electric vehicles with ultra high efficiency. In Proceedings of the IEEE Energy Conversion Congress and Exposition, Pittsburgh, PA, USA, 14–18 September 2014; pp. 668–674. [Google Scholar]
- Chen, W.; Liu, C.; Lee, C.H.T.; Shan, Z. Cost-effectiveness comparison of coupler designs of wireless power transfer for electric vehicle dynamic charging. Energies
**2016**, 9, 906. [Google Scholar] [CrossRef] - Kurs, A.; Karalis, A.; Moffatt, R.; Joannopoulos, J.D.; Fisher, P.; Soljačić, M. Wireless power transfer via strongly coupled magnetic resonances. Science
**2007**, 317, 83–86. [Google Scholar] [CrossRef] [PubMed] - Daerhan, D.; Hu, H.; Georgakopoulos, S.V. Novel topologies of misalignment insensitive SCMR wireless power transfer systems. In Proceedings of the IEEE Antennas and Propagation Society International Symposium, Memphis, TN, USA, 6–11 July 2014; pp. 1341–1342. [Google Scholar]
- Jolani, F.; Yu, Y.; Chen, Z. Enhanced planar wireless power transfer using strongly coupled magnetic resonance. Electron. Lett.
**2015**, 51, 173–175. [Google Scholar] [CrossRef] - Wei, X.; Wang, Z.; Dai, H. A critical review of wireless power transfer via strongly coupled magnetic resonances. Energies
**2014**, 7, 4316–4341. [Google Scholar] [CrossRef] - Liu, D.; Hu, H.; Georgakopoulos, S.V. Misalignment sensitivity of strongly coupled wireless power transfer systems. IEEE Trans. Power Electron.
**2017**, 32, 5509–5519. [Google Scholar] [CrossRef] - Bao, K.; Hu, H.; Georgakopoulos, S.V. Design considerations of conformal SCMR system. In Proceedings of the IEEE Wireless Power Transfer Conference, Boulder, CO, USA, 13–15 May 2015; pp. 1–3. [Google Scholar]
- Hu, H.; Bao, K.; Gibson, J.; Georgakopoulos, S.V. Printable and Conformal Strongly Coupled Magnetic Resonant systems for wireless powering. In Proceedings of the 2014 IEEE 15th Annual Wireless and Microwave Technology Conference (WAMICON), Tampa, FL, USA, 6 June 2014; pp. 1–4. [Google Scholar]
- Gibson, J.; Bao, K.; Hu, H.; Georgakopoulos, S.V. Wireless charging for Li-Ion battery using a printable Conformal SCMR. In Proceedings of the IEEE Antennas and Propagation Society International Symposium, Toronto, ON, Canada, 11–17 July 2010; pp. 1349–1350. [Google Scholar]
- Sample, A.P.; Meyer, D.T.; Smith, J.R. Analysis, experimental results, and range adaptation of magnetically coupled resonators for wireless power transfer. IEEE Trans. Ind. Electron.
**2011**, 58, 544–554. [Google Scholar] [CrossRef] - Nair, V.V.; Choi, J.R. An efficiency enhancement technique for a wireless power transmission system based on a multiple coil switching technique. Energies
**2016**, 9, 156. [Google Scholar] [CrossRef] - Beh, T.C.; Imura, T.; Kato, M.; Hori, Y. Basic study of improving efficiency of wireless power transfer via magnetic resonance coupling based on impedance matching. In Proceedings of the 2010 IEEE International Symposium on Industrial Electronics, Bari, Italy, 4–7 July 2010; pp. 2011–2016. [Google Scholar]
- Hu, P.; Ren, J.; Li, W. Frequency-splitting-free synchronous tuning of close-coupling self-oscillating wireless power transfer. Energies
**2016**, 9, 491. [Google Scholar] [CrossRef] - Park, J.; Tak, Y.; Kim, Y.; Kim, Y.; Nam, S. Investigation of adaptive matching methods for near-field wireless power transfer. IEEE Trans. Antennas Propag.
**2011**, 59, 1769–1773. [Google Scholar] [CrossRef] - Noriaki, O.; Kenichiro, O.; Hiroki, K.; Hiroki, S.; Shuichi, O.; Tasuku, M. Efficiency improvement of wireless power transfer via magnetic resonance using transmission coil array. In Proceedings of the 2011 IEEE International Symposium on Antennas and Propagation, Spokane, WA, USA, 3–8 July 2011; pp. 1707–1710. [Google Scholar]
- Liu, F.; Yong, Y.; Jiang, D.; Ruan, X.; Chen, X. Modeling and optimization of magnetically coupled resonant wireless power transfer system with varying spatial scales. IEEE Trans. Power Electron.
**2017**, 32, 3240–3250. [Google Scholar] [CrossRef] - Mou, X.; Groling, O.; Sun, H. Energy efficient and adaptive design for wireless power transfer in electric vehicles. IEEE Trans. Ind. Electron.
**2017**. [Google Scholar] [CrossRef] - Xie, X.; Bucknall, R.W.G.; Yearwood, K. Simulation study of a magnetic coupled resonant wireless energy transfer and storage system for electric vehicles under dynamic condition. In Proceedings of the Australasian Universities Power Engineering Conference, Brisbane, Australia, 25–28 September 2015; pp. 1–6. [Google Scholar]
- Jonah, O.; Georgakopoulos, S.V. Wireless power transfer in concrete via strongly coupled magnetic resonance. IEEE Trans. Antennas Propag.
**2013**, 61, 1378–1384. [Google Scholar] [CrossRef] - Kahng, S. Enhanced Coupling Structures for Wireless Power Transfer Using the Circuit Approach and the Effective Medium Constants (Metamaterials), Wireless Power Transfer Principles and Engineering Explorations. Available online: www.intechopen.com/books/wireless-power-transfer-principles-and-engineering-explorations/enhanced-coupling-structures-for-wireless-power-transfer-using-the-circuit-approach-and-the-effectiv (accessed on 6 January 2017).
- Theilmann, P.T.; Asbeck, P.M. An analytical model for inductively coupled implantable biomedical devices with ferrite rods. IEEE Trans. Biomed. Circuits Syst.
**2009**, 3, 43–52. [Google Scholar] [CrossRef] [PubMed] - Lu, X.; Wang, P.; Niyato, D.; Kim, D.I.; Han, Z. Wireless charging technologies: Fundamentals, standards, and network applications. IEEE Commun. Surv. Tutor.
**2016**, 18, 1413–1452. [Google Scholar] [CrossRef] - Karalisa, A.; Joannopoulos, J.D.; Soljačić, M. Efficient wireless non-radiative mid-range energy transfer. Ann. Phys.
**2008**, 323, 34–48. [Google Scholar] [CrossRef] - Bouattour, G.; Kallel, B.; Sasmal, K.; Kanoun, O.; Derbel, N. Comparative study of resonant circuit for power transmission via inductive link. In Proceedings of the IEEE International Multi-Conference on Systems, Signals & Devices (SSD15), Sfax, Tunisia, 16–19 March 2015; pp. 1–6. [Google Scholar]
- Hu, H.; Georgakopoulos, S.V. Design of optimal and broadband conformal SCMR systems. In Proceedings of the IEEE Antennas and Propagation Society International Symposium, Memphis, TN, USA, 6–11 July 2014; pp. 1345–1346. [Google Scholar]
- Li, X.; Dai, X.; Li, Y.; Sun, Y.; Ye, Z.; Wang, Z. Coupling coefficient identification for maximum power transfer in WPT system via impedance matching. In Proceedings of the IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer, Knoxville, TN, USA, 4–6 October 2016; pp. 27–30. [Google Scholar]
- Ramaswamy, V.; Edison, A.S.; Brey, W.W. Inductively-coupled frequency tuning and impedance matching in HTS-based NMR probes. IEEE Trans. Appl. Supercond.
**2017**, 27, 1502505. [Google Scholar] [CrossRef] - Huang, Y.; Shinohara, N.; Mitani, T. Impedance matching in wireless power transfer. IEEE Trans. Microw. Theory Tech.
**2016**, 65, 582–590. [Google Scholar] [CrossRef]

**Figure 4.**Simulated efficiency of the hybrid system using the calculated equation for the distance $\left({d}_{12}\right)$.

**Figure 8.**Frequency misalignment between the mathematical model at 7.2 MHz and the experimental setup at 7.22 MHz.

**Figure 10.**Measured combined SCMR-CSCMR system the holding maximum efficiency at a frequency of 7.23 MHz.

**Figure 11.**The relation between the distances ${d}_{12}$ and ${d}_{23}$ and a measured distance ${d}_{12}$.

**Figure 14.**Measured angle efficiency of the combined system for various angles between transmitter and receiver.

**Figure 16.**Measured misalignment efficiency of the combined system for various positions of the receiver.

${\mathit{R}}_{\mathit{S}};{\mathit{R}}_{\mathit{L}}$ = 50 | ${\mathit{r}}_{1}={\mathit{r}}_{2}={\mathit{r}}_{3}$ = 30 mm | ${\mathit{r}}_{4}$ = 5 mm |
---|---|---|

${R}_{1}$ = 0.015 $\mathsf{\Omega}$ | ${C}_{1}$ = 525.97 pF | ${L}_{1}$ = 0.929 $\mathsf{\mu}$H |

${R}_{2}$ = 0.03 $\mathsf{\Omega}$ | ${C}_{2}$ = 203.42 pF | ${L}_{2}$ = 2.402 $\mathsf{\mu}$H |

${R}_{3}$ = 0.02 $\mathsf{\Omega}$ | ${C}_{3}$ = 661.2 pF | ${L}_{3}$ = 0.739 $\mathsf{\mu}$H |

${R}_{4}$ = 0.012 $\mathsf{\Omega}$ | ${C}_{4}$ = 2571.1 pF | ${L}_{4}$ = 0.19 $\mathsf{\mu}$H |

**Table 2.**Comparison between the measured and calculated distances (${d}_{12}$) and variation between the two in %.

${\mathit{d}}_{23}$ (mm) | Calculated ${\mathit{d}}_{12}$ (mm) | Measured ${\mathit{d}}_{12}$ (mm) | Variation (%) |
---|---|---|---|

3 | 1 | 1 | 0 |

4 | 1.3 | 1 | 23 |

5 | 1.6 | 1.5 | 6.2 |

6 | 1.9 | 1.8 | 5.2 |

7 | 2.2 | 2 | 10 |

8 | 2.5 | 2.3 | 8 |

9 | 2.8 | 2.6 | 7.1 |

10 | 3.1 | 2.9 | 6.4 |

11 | 3.4 | 3.2 | 5.8 |

12 | 3.7 | 3.6 | 2.7 |

13 | 4 | 4.1 | 0.4 |

14 | 4.3 | 4.5 | 4.6 |

15 | 4.6 | 4.9 | 6.5 |

16 | 4.9 | 5 | 2 |

17 | 5.2 | 5.3 | 1.9 |

18 | 5.5 | 5.6 | 1.8 |

19 | 5.8 | 5.9 | 1.7 |

20 | 6.1 | 6.1 | 0 |

21 | 6.4 | 6.1 | 4.6 |

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**MDPI and ACS Style**

Rozman, M.; Fernando, M.; Adebisi, B.; Rabie, K.M.; Kharel, R.; Ikpehai, A.; Gacanin, H.
Combined Conformal Strongly-Coupled Magnetic Resonance for Efficient Wireless Power Transfer. *Energies* **2017**, *10*, 498.
https://doi.org/10.3390/en10040498

**AMA Style**

Rozman M, Fernando M, Adebisi B, Rabie KM, Kharel R, Ikpehai A, Gacanin H.
Combined Conformal Strongly-Coupled Magnetic Resonance for Efficient Wireless Power Transfer. *Energies*. 2017; 10(4):498.
https://doi.org/10.3390/en10040498

**Chicago/Turabian Style**

Rozman, Matjaz, Michael Fernando, Bamidele Adebisi, Khaled M. Rabie, Rupak Kharel, Augustine Ikpehai, and Haris Gacanin.
2017. "Combined Conformal Strongly-Coupled Magnetic Resonance for Efficient Wireless Power Transfer" *Energies* 10, no. 4: 498.
https://doi.org/10.3390/en10040498