| Aiming at the traditional contact charging mode for electric automobiles has security risks and not convenient, it causes the generation of wireless power transmission technology. Compared with the traditional contact charging mode, wireless power transmission technology is more flexible and convenient. There are many factors that affect the efficiency of wireless power transmission, such as the size of the coupling factor, frequency stability during transmission, electromagnetic compatibility and impedance matching.In this thesis, the problem of impedance matching was studied, which has a great impact on the efficiency of wireless power transmission technology. Compared with traditional impedance matching technology, the dynamic impedance matching system can do real-time, fast and stable matching for dynamic loads. It can improve the efficiency of the wireless power transmission and maximize the power transmission.The different impedance characteristics of equivalent power supply side and the battery load side was analyzed in this paper, especially for the latter, an improved equivalent circuit model of the lead-acid battery was established, and the equivalent mathematical model of the battery based on the improved equivalent circuit model of the battery was derived, then the dynamic impedance curves of the battery load was acquired under Matlab/Simulink environment.After depth understanding of the principle of impedance matching, static impedance matching was analyzed used smith chart, according to the load of this paper, improved the common impedance matching network, a new Γ type impedance matching network was designed and its parameters’range were estimated.A dynamic impedance matching system which includes central processing module, variable parameter adjustment module and reflection coefficient detection module was designed. A stepper motor control was introduced in the variable parameter adjustment module, and put the parameter position information into the central processing module. A scheme which can simultaneously detect the reflection coefficient’s modulus value and phase was presented in the reflection coefficient detection module, which can improve the matching speed of the whole system.The optimization algorithms of dynamic impedance matching were deeply researched, which include coordinate rotation algorithm, steepest descent algorithm, simulated annealing algorithm and particle swarm algorithm. According to the disadvantages of these algorithms, a new kind of optimization algorithm for the dynamic impedance matching system was adopted. The Matlab/simulink simulation results showed that the designed impedance matching system in this thesis can achieve the dynamic adaptive impedance matching. |
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