Study on Series-parallel Mixed-resonance Model of Wireless Power Transfer via Magnetic Resonance Coupling

Wireless power transfer system via magnetic resonance coupling (WPT/MRC) displays its superiority in its higher efficiency, longer range and greater power output. Up to now, diverse circuit architectures are widely utilized in WPT system. This paper conducts research on series-parallel mixed-resonance (SPMR) model, by analyzing the equivalent circuit model using circuit theory, the effects that the coupling coefficient between the coils, compensation capacitance ratio and load resistance may have on the efficiency and the output power are elaborated, and the general expressions for symmetry and asymmetric SPMR WPT systems of efficiency and power were obtained. Furthermore, the general expressions can be used in the analysis for the four basic topologies (series-series, series-parallel, parallel-series and parallel-parallel) by setting the compensation capacitance ratio as 1 or 0. Numerical calculated by the Matlab software and circuit simulated by Advanced Design System (ADS), the results show that the compensation capacitance ratio of SPMR topology plays a crucial role in WPT system. Compared with common series-series model, by optimizing the compensation capacitance ratios, the efficiency of SPMR WPT system can not only be improved effectively, but also the output power can be enlarged when the coil distance is far. Additionally, optimum loads of the best efficiency point and maximum power point are changeable under the condition of changing distance. Consequently, the SPMR circuit has great practicability and transfer performance. A wireless power transfer system with series-parallel mixed-resonance structure via magnetic resonance coupling is designed and created in this paper and the correctness of the aforementioned theoretical analyses and calculation simulation is verified through the experimental results.