Compensation Topology And Parameter Optimization For High-power Capacitive Power Transfer System

Wireless power transfer(WPT)system can solve the disadvantages of leakage,spark,etc.,caused by the traditional contact-wire power supply method,is an important development direction for the power supply system.At present,WPT mainly includes magnetic field coupling and electric field coupling.The former is named Inductive power transfer(IPT),which uses a magnetic field to build the power transfer channel and requires many high-frequency Litz wires and magnetic cores to produce the IPT coupler.And the latter is called Capacitive power transfer(CPT),which uses an electric field as the transmission medium.Only the thin and cheap metal plates are usually adopted to make a CPT coupler.Compared with the IPT system,the CPT system has the advantages of low construction cost,the lightweight of the coupling coupler,and no eddy current loss in the nearby metal objects.Therefore,the CPT system has attracted the attention of a large number of researchers all around the world and is developing rapidly in recent years.However,the coupling capacitance of the CPT system is really small.When the transfer distance reaches hundreds of mm,the coupling capacitance is in only p F level,which brings a big challenge for designing the high-power CPT system in the safe and reliable operation,transfer power enhancement,and high coupler misalignment tolerance.Limited by the working frequency of the inverter switching devices and the coupling mechanism’s available space size,the current system’s transfer power mainly depends on improving the transmission voltage of the coupling mechanism.At present,to achieve a k W level power transmission,the coupling coupler’s voltage has reached several k V.For higher power demanded applications such as railway power supply system,the high voltage stress will bring significant risks to the CPT coupler and compensation topology.In contrast,the traditional CPT topology and its parameters have been challenging to meet the highpower transfer of k W level and above.In this dissertation,I have carried out a series of researches on the high-power CPT system to deal with the problems mentioned above.The main work of this paper can be summarized as:1.To solve high voltage stress on the CPT coupler in a high-power system,the boundary condition of the maximum transfer power of the CPT coupler is analyzed.The compensation topology structure and parameter configuration of the transmitter and receiver under the maximum transfer is obtained.Based on this method,the port voltages of the CPT coupler boosted by the transmitter/receiver topology are all utilized to transfer the active power,which can reduce the requirements for the coupler voltage for the high-power CPT system.The experimental results show that the proposed compensation topology and parameter configuration can realize that the phase difference of the port voltage is 90° and verify that the coupler’s port voltage can be all used for CPT power transfer.2.A double-sided CL compensation topology is proposed for the high-power and large-airgap CPT systems considering the high votlage stressed on the system componnets.Based on this topology,a voltage optimization method is proposed to distribute the passive components’ component voltages.This method can effectively reduce the maximum voltage to ensure a safe and reliable system operation.The experimental results show the effectiveness of this method.3.Given the single transmission channel of the CPT system,which cannot effectively improve the system power,this paper proposes a hybrid system of CPT and IPT.The operational characteristics of the CPT and IPT systems are analyzed.The coupler connection method of a CPT-IPT hybrid system is given based on the transfer power enhancement.A CPT-IPT hybrid system with a series-series(SS)compensated topology is proposed.The experimental platform’s experiment results show that the hybrid system can achieve a higher power transfer than a single CPT or IPT system under the same voltage and current limiting conditions.4.To solve the problem that the output of a high-power CPT system changes dramatically when the coupling coupler deviates,a novel LCCLC compensation topology is proposed in this paper.With the proper compensation parameter optimization,this topology can effectively improve the CPT coupler’s anti-misalignment performance.Based on the voltage optimization method,the design process of the compensation parameters is given.The influence mechanism of the coupling coupler against the system output power under the misalignment is clarified.