Design Of Coupling Coil For Wireless Power Transfer System Of Trams

As a new public transportation, modern tram has many advantages, such as high-speed, low construction cost, short construction cycle, energy conservation and environment protection. This paper has combined the technology of wireless power transfer with the modern tram, and then analyzed the system parameters which can influence the system transmission efficiency and the output power by the theory of mutual inductance model. In addition to this, this paper has showed three kinds of commonly used structures of coupling coil, these structures are circular, square, and Double-D(DD), respectively, then compared the transmission performance of the three structures. In order to decrease the mutual inductance for high power transmission, and lower the design requirements of coupling coil, this paper has proposed a new transmission model of WPT (wireless power transfer) system which has one primary side and multiple secondary sides. In order to further verify the correctness of the proposed model, simulation and experiment are presented by PSIM and experimental platforms, respectively.Firstly, after analyzing and choosing the basic compensation topology of the coupling coil, the theoretical derivation and analysis of the WPT system characteristic can be conducted by using the principle of mutual inductance equivalent. Then analyzing the factors which can affect the wireless power transfer system, the factors include the changes of the load, operating frequency, the value of mutual inductance and so on.Secondly, this paper comparing and analyzing some different structure of the coupling coils. First, the constraints of coupling coil in the application of modern tram have been confirmed, and the effect of the coupling coil performance has been analyzed, which under the change of horizontal displacement and vertical spacing by using the electromagnetic simulation software of Maxwell Ansoft. Second, this paper has compared the influence degree to rail under the alternating magnetic field which has been produced by alternating current, when the three kinds of coupling coil are under the normal work mode. At last, an analysis of coupling coil performance has been presented on the number of magnetic core and the spacing of the magnetic core. Based on the above, the DD type structure of the coupling coil is more suitable for application in the tram. In this paper, a traditional model of WPT with one primary side and multiple secondary sides has been proposed, aiming at reducing the mutual inductance value in high power transmission, reducing the design requirements, reducing the current and voltage stress and improving the transmission efficiency of the whole system. Then the theoretical derivation on the model of one single primary coil and multiple secondary coils has been presented. At last, the theory has been verified by the simulation software, which is called PSIM, and the correctness and rationality of this system is verified by simulation, which take the super-capacitor load for example.Finally, an experimental platform of 1kW has been built based on the theory and the simulation model of chapter four, including the design of main circuit, the design of drive circuit. Through to contrast the data between the small size model of coupling coil and Ansoft simulation model, it can be concluded that the finite element simulation software can be used to study the coupling coil performance accurately. By comparing the experimental waveforms, the results are presented to verify the feasibility and effectiveness of the proposed transmission model. In the end, this paper introduced the 50kW-WPT system briefly.