| The development of science and technology is advancing at a high speed in this rapidly changing society.More and more electronic devices have entered our daily life,such as non-mobile air conditioners and desktop computers and mobile phones and tablets so that more and more power lines and charging lines are used.The proliferation of wires and data lines not only appears cluttered,but also cannot adapt to some special working environments,and even bring certain safety hazards such as fire caused by the aging of the line.Therefore,wireless power transfer(WPT)technology has attracted more and more attention and research.Magnetic coupling resonant wireless power transfer(MCR-WPT)technology was first proposed in 2007 and has become a research hotspot in recent years due to its advantages of high transmission efficiency,long transmission distance and overcoming obstacles.A lot of scholars have focused their research on the improvement of working principles,circuit topology,transmission distance and the efferent efficiency,and have achieved remarkable results.However,power security has gradually become a problem that cannot be ignored with the development and application of wireless power transmission.It is the direction of this study that how to ensure that the authorized user's power is not illegally stolen when there are multiple power receivers,and how to reduce the interference to the surrounding sensitive electromagnetic equipment.This dissertation,therefore,designs a wireless power encryption transmission system by using the MCR-WPT and spread spectrum technologies.First,the working mechanism and structural composition of the MCR-WPT system are described.The model is established through the coupled mode theory and equivalent circuit mutual inductance theory,the system power transfer efficiency expression is introduced and the main factors affecting the system performance are analyzed.On the premise of fixing each parameter,the conditions to be satisfied by the system resonator and the resonant frequency when oscillating power exchange is maximized are verified by simulating experiments.Second,a basic MCR-WPT system was designed and implemented.Various modules such as driving circuit,inverter circuit and resonant network were designed and simulated by LTSPICE simulation software.The hardware platform of MCR-WPT system was realized based on the schematic diagram.Thirdly,a wireless power encryption strategy based on spread spectrum technology is designed according to the characteristics of frequency sensitivity of MCR-WPT technology.The frequency hopping system is simulated by matlab/simulink,its working principle,system performance and encryption principle are analyzed,and then a multi-access wireless power encryption strategy with certain scalability is designed.Finally,according to the power encryption strategy,various parts of the circuit are improved and simulated by LTSPICE simulation software.In order to reduce the complexity of system control,the launch circuit based on Royer self-excited oscillation circuit was designed.The key generation unit was written by matlab/simulink,and the generated key drive waveform was imported into LTSPICE to complete the simulation.The experimental results show that the authorized users can always receive power stably and efficiently,and the power received by the illegal recipients is suppressed by more than 75%,thus verify the rationality and feasibility of the wireless power encryption transmission system. |
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