Research On Energy Encryption Technology For Wireless Power Transfer System Of Three-Coil Structure

As a new power transfer technology,wireless power transfer(WPT)technology brings great convenience to people’s life style by virtue of flexible power supply mode and good penetration performance to non-metallic obstacles.With the increasing demand for commercialization of WPT technology,reducing the risk of "electricity theft" in the process of power transmission and avoiding irrelevant load or illegal load sharing power transmission channel become the premise of further commercial application of WPT technology,which is also the significance of this paper.Based on this background,the energy encryption technology of three-coil magnetic coupled resonant wireless power transmission system is studied in this paper.The equivalent model of three-coil magnetic coupling resonant wireless power transfer(MCRWPT)system is established based on circuit theory,and the formulas of output power and efficiency of three-coil MCRWPT system are derived.Because there are many system parameters in the formula,the functional relationship between system load,mutual inductance coefficient,compensation capacitance and output power,and system efficiency is analysed by using control variable method and MATLAB software,which directly shows the influence of single system parameter on system output power and system efficiency.The above analysis not only provides a reference for building the hardware circuit platform of the system,but also draws the conclusion that the energy encryption of MCRWPT system can be realized by changing the capacitance of the secondary compensation capacitor.The basic characteristics of chaos theory are introduced.The bifurcation diagram of Logistic mapping is drawn and its encryption mechanism is analyzed.Considering that the capacitance of the secondary compensation capacitor can affect the output power and system efficiency,a three-coil structure MCRWPT energy encryption strategy based on Logistic mapping is designed.In order to verify the correctness and feasibility of the strategy,the hardware circuit platform of the energy encryption device of the three-coil MCRWPT system is designed and the related experiments are carried out.Under the condition of the system transmission distance of 18 cm and the input voltage of 80 V,the experimental results show that the maximum output power of the legitimate side coil is 256 W,the minimum output power is 242 W,the average system efficiency is about 82.8%.The maximum output power of the illegal side coil is 11 W,the minimum output power is 8.5W,the average system efficiency is 20.6%.