| In recent years,the traditional wired power supply system has been unable to satisfy people’s requirements for mobility and special occasions because mobile devices develop rapidly,and there are some outstanding problems(such as electric spark and non-smart power supply)in the traditional wired power supply system.These factors brings many potential safety hazards to people when using electric energy.More importantly,in some special occasions,the wired power supply mode does not meet the requirements of these special occasions.Therefore,wireless power transfer(WPT)technology has become a research hotspot.Compared with wired power supply,the advantage of wireless power transfer is that there are no problems such as wear and sparks.But its transfer performance is easily affected by parameters and environmental changes.In order to explore the impact of parameter or environmental changes on system performance,this article focuses on the frequency characteristics and frequency tracking methods of the more string-type two-coil and three-coil magnetic coupling resonant wireless power transfer systems that are used in reality.Aspects of research.Among them,the study of frequency characteristics can know what kind of impact the system will have when the external environment or parameters change,and the study of frequency tracking methods can solve the problem of system performance degradation when the system is detuned due to external environment or parameter changes.problem.The research content of this article mainly includes the following aspects:First,according to the transmission mechanism of the MCR-WPT system,a circuit model is established using the theory of mutual inductance,and the expression of the compensation capacitance value of the MCR-WPT system of various topologies is deduced,and the string topology is selected as the research object.Secondly,the frequency characteristics of the two-coil MCR-WPT system,which is currently the most widely used,is studied.Although the current research on the frequency characteristics of the two-coil MCR-WPT system is endless,most of the research stays on the load change or the change of the transmission distance.There are few studies on how the system frequency characteristics change when the compensation capacitance of the system changes.Therefore,this thesis studies The frequency characteristics of the system when the capacitance changes are compensated,the calculation formula of resonant frequency,and the expression of resonant frequency,efficiency and output power are deduced,and MATLAB is used for simulation analysis,and then a complete set of experimental equipment is established.The correctness of the calculation and simulation is verified,and the influence of the compensation capacitance change on the frequency characteristics of the system is well revealed.Thirdly,based on the frequency characteristics of the two-coil MCR-WPT system,the frequency characteristics of the three-coil MCR-WPT system when a relay coil is added are studied.Compared with the two-coil structure,the three-coil structure has higher efficiency and transmission power,but the application of the three-coil system is not so extensive at present,and the research on its frequency characteristics is even less.Therefore,this thesis studies the frequency characteristics of the three-coil MCR-WPT system when several typical coil positions are changed,and also derives the calculation formula of its resonant frequency,as well as the expression of resonant frequency,efficiency and output power.Then MATLAB simulation was used to verify the correctness of the calculation formula,and a set of three-coil MCR-WPT system experimental device was developed to verify the correctness of the simulation and calculation.The simulation and experimental results are basically the same,and it can be seen through simulation and experiment.Which coil position changes have a greater impact on the resonant frequency,efficiency and power of the system,which has guiding significance for the three-coil MCR-WPT system to obtain high power and high efficiency at the same time.Finally,the frequency tracking method of the MCR-WPT system based on the phase-locked loop,which is currently widely used,is studied,and a simulation model of the entire system is built through Simulink.The simulation results show that the method can be compensated in the transmitting coil or the receiving coil.When the capacitance changes,the input voltage and current of the transmitter will resonate,and the latest resonant frequency of the system can be automatically tracked to make the system automatically in resonance. |
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