Research On High Efficiency And Stable Magnetically Coupled Wireless Power Transfer System

Wireless power transfer(WPT)technology has been in development for more than100 years since Tesla’s experiments in the 19 th century.In recent years,due to the development of inductive power transfer(IPT)and magnetically coupled resonance wireless power transfer(MCR-WPT),there are more and more wireless power transfer technologies appearing in various application scenarios,such as smart home and various consumer electronic products,smart electric vehicles,active medical implanted devices,and wireless network sensors,etc.Compared with wired power transmission,wireless power transfer technology has wider application scenarios,so this technology has also attracted the attention,discussion and research of a large number of researchers.Nowadays,the key point of wireless power transfer technique is to enhance its transport performance,such as maximum transfer efficiency and maximum transfer distance in a given efficiency.However,regardless of the maximum transfer efficiency or the maximum transfer distance,there should be no change in the relative location of the transmitter and the receiver.Once the change occurs,the efficiency will drop sharply,which has become one of the most important reasons for limiting the application of wireless power transfer technology.At the same time,different types of receivers can also cause changes in output parameters such as voltage,current,power,or efficiency.Therefore,it is very important to study high efficiency and stability of magnetic coupling wireless power transfer system.In view of the above problems,this dissertation proposes solutions to reduce the influence of different types of receivers on the output parameters and the loss of efficiency due to the difference between the sender and the receiver are analyzed.The concrete research content is composed of four parts:1.Study of independent WPT systems with multiple receiver loads.The T-type compensation network is added to the three receivers,and Kirchhoff’s law is used to derive the relationship between the output voltage and the load.When the circuit parameters satisfy the imaginary part of the denominator equal to zero,the output voltage can be independent of the load.Further,the capacitance in the T-type compensation network is optimized by MATLAB,so that the loads at three different positions can receive the same voltage,while still retaining the load independence characteristic.Simulation and experiments have verified it.The results show that when the load output voltages at three different positions are different,the efficiency is higher,and the three voltages do not change with the load.When the load output voltages at the three different positions are the same,the efficiency is reduced,but the voltage of the three also does not change with the load.2.Research on high stability WPT systems suitable applied to the active medical implant equipment.A simple inverted L-type compensation network is added to the transmitter,and Kirchhoff’s law is used to obtain the relational expression between the output voltage and the coupling coefficient,and the relational expression is derived.MATLAB is used to optimize the circuit parameters of the inverted-L compensation network so that the coupling coefficient is changed in a given range,the output voltage is kept relatively stable.It is proved by simulation and experiment that the variation ratio of the output voltage is less than 5%.At the same time,the specific absorption rate characteristics of the system are also analyzed,and the simulation results indicate that the performance of the system is in the safety range.3.Design method of high stability WPT systems based on filter theory.Compare the amplitude response expression of the filter with the efficiency expression of the wireless power transfer system,take the coupling coefficient and the load as variables respectively,regard the remaining terms as coefficient terms and constant terms,and make them proportional to the coefficients in the filter,then a high-stability wireless power transfer system within a certain range can be designed by using the passband characteristics of the filter.Experiments demonstrate that the system can combat the efficiency drop caused by distance and misalignment while maintaining a stable efficiency under load variations.4.Design a high-stability WPT system using high-order filter theory.Four-coil and six-coil wireless power transfer systems are designed using the second-order filter and third-order filter theory.Similar to the case of the first-order filter,the coefficient terms and constant terms are equal to the coefficient terms and constant terms of the filter,and then the circuit parameters can be solved.Compared with the high-stability wireless power transfer system designed by using the first-order filter,the wireless power transfer system has a greater range of variation in distance,moreover,it can keep the loadindependent property.The simulation and experimental results show that the proposed approach is correct.In practical application scenarios,the wireless power transfer system designed by a suitable high-order filter can be selected according to the required distance variation range.