Study Of Cascaded Capacitive Power Transfer System For Multiple Loads Application

Wireless Power Transfer(WPT)technology uses transmission medium to realize noncontact transmission of electric energy.With its advantages of convenience and safety,WPT has become a novel electric power supply method that can replace traditional wired contact power supply.As one of the main methods of WPT technology,Capacitive Power Transfer(CPT)technology utilizing high-frequency electric field to transfer energy has attracted extensive attention,and has the characteristics of low loss of eddy current,as well as suitable for metal environment situation.Recently,the researches of CPT system mainly focus on the single input and single output system,while there are a few works concentrated on the multiple-loads CPT technology.When the loads are distributed vertically or separated far away,such as reefer container and heavy-haul train Electronically Controlled Pneumatic(ECP)brake system,the existing CPT technologies cannot supply power effectively.In order to solve the above issues,a cascade multi-load CPT system structure is proposed in this paper.Unlike the traditional multi-load CPT system,where receivers function solely as power consumers,in the proposed system,each receiver not only supplies power to the connected load but transfers power wirelessly to the next receivers.The proposed CPT system can effectively expand the macroscopic transmission distance and charging freedom of the CPT systemIn this paper,two coupler structures for cascaded CPT system are proposed for the applications of reefer container and heavy-haul train ECP braker.The equivalent π type circuit and equivalent controlled source model of the two coupler structures are established.Secondly,the compensation topologies of cascaded CPT system with isolation structure and without isolation structure are proposed for two different application scenarios.The mathematical models of compensation topologies on output characteristics are established.Then,the output characteristics,system efficiencies and voltage press on compensation elements of the proposed CPT system are analyzed,considering the impact of the parasitic resistance.Finally,the compensation parameters design methods are given,and a 1.8kW(600W&600W&600W)and a 150W(50W&50W&50W)simulation and experimental prototype with three loads are built to validate the effectiveness of the proposed CPT systems.The optimum experimental system efficiency can reach 83.7% and 81.5%respectively.The equal power distributions are achieved,and disconnections of each load would not affect the normal operation of other loads.