| With the development of wireless power transfer(WPT)technology,multi-load wireless power transfer system has gradually become one of the research hotspots in recent years.However,the output stability of the existing multi-load WPT system is easily affected by the coupling coefficient.When the coupling coefficient changes,it is difficult to maintain constant output power and constant transfer efficiency,resulting in anti-offset ability and low spatial degree of freedom.In addition,how to achieve the power distribution among different loads according to the actual needs is also the main challenge of multi-load WPT system.Therefore,in order to solve the above problems,based on parity time symmetry(PT symmetry)theory,this paper proposes a new multi-load WPT system with constant output characteristics,which achieves constant output power and constant transfer efficiency under the condition of variable coupling coefficient,and then proposes the corresponding power distribution control strategy.The main research contents of this paper include:Firstly,the circuit modelling of PT-symmetric WPT(PT-WPT)system is carried out,and the transmission characteristics of single-load PT-WPT system are analysed in detail,which lays a theoretical foundation for the analysis of multi-load PT-WPT system.Secondly,a single-frequency multi-load PT-WPT system is proposed.Based on the system model,the frequency characteristics,current and voltage gain,output power and transfer efficiency of the system are analysed in turn,and then the power distribution relationship among different loads is deduced.A power distribution control method controlled by the coupling coefficient is proposed to realize constant output characteristics of each load.Thirdly,in order to overcome the shortcoming that the power distribution of the singlefrequency multi-load PT-WPT system is controlled by the coupling coefficient,a multifrequency multi-load PT-WPT system is proposed.By dynamically adjusting the series resonant capacitance of the transmitter,the system has different natural resonant frequencies at different times.Furthermore,a power distribution control method controlled by the switch duty cycle αis proposed,which makes the power distribution relationship among loads independent of the coupling coefficient and maintains the advantages of constant output characteristics of each load.Finally,the design process of the core part of the multi-load PT-WPT system is described in detail,and the prototype is made.The experiments of single-frequency multi-load PT-WPT system and multi-frequency multi-load PT-WPT system are carried out respectively,which verify the correctness of the theoretical analysis and the feasibility of the control method. |
