| Magnetic coupling resonance wireless power transmission as an emerging technology has attracted much attention in recent years. It has wide application prospects for the intelligent home system, portable electronic devices and rail transportation area. The basic principle of the magnetic coupling resonance is that when the operating frequency of high frequency power supply and the inherent frequency of the transmission coil are the same, long-range, high efficiency wireless energy transmission can be achieved via electromagnetic field in the near field. In order to improve the transfer performance, this paper optimized and analyzed the design of coupling coils, focusing on the most commonly used circular and rectangular planar spiral coil.Firstly an equivalent circuit theory model was established to analyze the energy transfer between transmitting and receiving coil, the maximum transmission efficiency and output power. The main factors affecting the transmission characteristics of the system are the coupling coefficient and quality factor of the coils. For the analysis of coil mutual inductance, two mathematical models were built by means of partial element equivalent circuit method, and their numerical expressions of mutual inductance were given. Then the distribution of magnetic field intensity was mapped out using2D finite element analysis tool, and it was easy to find out the best position and angle of the receiving coils.In order to improve the coupling coefficient of two coils, the planar ferrite cores were added beneath the coils. Magnetic mirror models were adopted to calculate the mutual inductance of four transmission set configurations, and finite-width mirror model was obtained through the simulation, providing the theoretical basis for practical applications. After that the mutual inductance was measured using voltmeter-ammeter method, and the effect of mutual inductance and phase characteristics with different operating frequency was tested as well. Comparing the two planar spiral coils’mutual inductance under different transfer distance, the correctness of magnetic mirror model analysis was verified. The coupling characteristic of rectangular planar spiral coil is clearly better than the circular in the case of same size, and two plane-shaped cores added achieved the best performance for the coupling coils.Eventually, according to the optimization results a transmission device was built with litz wires. The coupling coefficient was significantly improved by the LCR meter. The frequency characteristics and transmission efficiency of two set of coils were tested, the results shows that the performance has improved significantly after optimization. The overall efficiency and output power were about83%and268.4W at the transfer distance8cm. At last, the electromagnetic environment was simulated when EV was wireless charging, the results showed that the chassis had a shielding effect and could protect vehicle occupants during the charging process. |
PDF Full Text Request