Optimization Design Research Of The S/P Compensated Contactless Resonant Converter Under Variable Parameters Condition

Wireless charging for Electric Vehicles(EVs) doesn't need cables which is used to connect EVs and ground power supplying in traditional charging ways. Therefore wireless charging technology has great advantages in safety, convenience and intelligence. However, contactless transformer need perfect alignment to ensure high-efficiency charging. If the transformer coils misalign, the operating condition of the charging system will deviate from the design point. The purpose of this thesis is to reach and optimal design the contactless resonant converter under variable parameters condition.Firstly, based on the comparisons of different compensation topologies, this thesis determines the S/P compensation to research. To facilitate the researches of the characteristics of S/P compensation under misalignment conditions, the relative self-inductance coefficient and relative mutual-inductance coefficient are introduced in the analysis. The voltage gain and phase characteristic of S/P compensation network at the fully tuned condition are researched by means of standardization. This thesis disclosed the relationships between the coupling coefficient and the voltage gain bifurcation point, the voltage gain peak point and the phase angle bifurcation point. By researching the voltage gain and phase characteristics under the condition of parameters variations, some special points, with unchanged voltage gain even at different parameters variations are given. Based on the input impedance analysis, the inductive region and the capacitive region are also determined. In order to ensure the soft-switch, the concept of inductive-overlap-region is put forward.Secondly, the thesis studies the selection of the fully tuned point considering the achievement of zero voltage switching, out voltage variations and the efficiency under the condition of parameters variations. Besides the performance analysis, the suitable control methods are also discussed. The optimal design process of full compensation point are given, which provide convenience for the design of wireless charger for electric vehicle.Finally, an 7.5kW prototype is developed and fabricated to verify the analysis. Experiments testify the effectiveness of the analysis. When the designed electric vehicle wireless charger output the rated power, the highest efficiency of the whole system is 92.21%, at the same time, the efficiency of the contactless resonant unit is 93.69%. When the air gap changes 50% and 20% of the lateral misalignment of the width of the transformer size is occurred, the wireless charger can still output power 5.05 kW stably, the system efficiency is 87.24%.