Research On Key Technologies Of Wireless Power Transfer Networks Based On Inductively Coupled Power Transfer

Wireless power transfer technology is a kind of power transmission technologybased on physical medium, such as high-frequency magnetic field, electromagneticwave, microwave, RF radio wave, etc, and is used to regulate the power transfer frompower source to pick-up side across an air-gap. Inductively coupled power transfer(ICPT) technology is a contactless power transmission technology based on inductivelycoupled principle, it has solved the problems on how to supply power to mobile devicessafely, flexibly and cleanly. It is a focus of wireless power transfer technology researchnow.The contradiction between power transfer efficiency and power transfer distance iscausing bottlenecks in the ICPT technology field. People have struggled to enlargewireless power transfer distance via heightening resonance frequency, strongly coupledmagnetic resonances, improving input power, optimization parameters of ICPT system,and so on. Power loss is concentrated on the circuit when frequency is low, withfrequency improving the power loss is concentrated in a space, power transferefficiency has been reduced greatly, EMI interfere is increasing, and the electronicdevice is affected. Power transfer efficiency is descending as power transfer distance isenlarged (MIT were able to transfer60watts with~40%efficiency over distances inexcess of2meters), it is unable to supply power to pick up when the primary sidepower is small. The primary side power increasing is limited because of the propertiesof semiconductor components. So the solutions are unable to radically solve the issuebetween power transfer efficiency and power transfer distance. At the same time， thegrowth of wireless power transfer technology based on electromagnetic wave,microwave, RF radio wave, etc has been restricted by power transfer distance, powertransfer efficiency, power transfer directional and so on.The paper has developed anovel concept of wireless power transfer networks based on wireless power transfertechnology, a series of power relay nodes are comprised of a power transfer link,through the power relay nodes the power transfer between the primary node and thepick-up node takes place, some power transfer links can compose the wireless powertransfer networks without a centre in networks, and with the peer to peer power transfernodes, to ensure wireless power transfer efficiency and enlarge wireless power transferdistance synchronously. The paper research activity is supported by the National Natural ScienceFoundation of the "Contactless power bi-directional push system key technologies"(Fund No.:50807057) and Research Fund for Doctor Station of Ministry of Education"Contactless power transfer system key technologies"(Fund No.:20070611012).Researching on key technologies of wireless power transfer networks based on wirelesspower transfer technology was implemented to demonstrate the technicality and validityof wireless power transfer networks.The main works of the paper include:1. The paper has analysed the domestic and foreign research status of wirelesspower transfer technology, a concept of wireless power transfer networks based onwireless power transfer technology has been proposed to resolve existing problems ofwireless power transfer technology, and has expatiated on research purpose, researchsignificance and content.2. The basic frame for wireless power transfer networks based on wireless powertransfer technology has been discussed, the paper has demonstrated the basicconfiguration of wireless power transfer node, the basic circuit topology, circuitimpedance analysis, hardware system and software system, and networks system ofwireless power transfer networks in detail. The feasibility of wireless unidirectionalpower transfer link has been validated.3. A phase shifting control strategy based on energy injection mode has been putforward for wireless power transfer regulation. Firstly the two operating modes ofwireless power transfer link have been introduced: energy injection mode and freerunning mode, and the paper dissertated the phase shifting control strategy based onenergy injection mode. The energy injection duty cycle concept has been proposed froman energy point of view to provide academic foundation for phase shifting controlstrategy. In the end, the validity for the phase shifting control strategy based on energyinjection mode has been argumented through simulation test.4. Because of the severe high-level switch non-linear characteristic of wirelesspower transfer link, it is hard to construct the mathematic model of wireless powertransfer link and control, so the voltage-stabilizing control strategy of wireless powertransfer link system based on neural network was brought forward. Firstly the paper hasanalysised the circuit topology, and designed the neural network based on the backpropagation algorithm for voltage-stabilizing control, the simulation results havetestified the feasibility of neural network controler. Finally the adaptability and robusticity of neural network controller has been verified by experiment results whenthe load changed.5. The circuit topology of wireless power bi-directional transfer based on ICPTtechnology was proposed. The operation mechanism of wireless power bi-directionaltransfer link has been discussed in the first place, the circuit topology of wireless powerbi-directional transfer link was expatiated via mutual inductance coupled principle, it isderived that both the amount and direction of power flow between the primary node andthe pick-up node can be regulated by controlling the relative phase angle betweenvoltages generated by primary node and pick-up node reversible rectifiers. For anygiven primary node and pick-up node phase angles, the power output can be regulatedby controlling the voltage magnitude generated by primary node reversible rectifier. Thecorrectness for the control strategy and the circuit topology of wireless powerbi-directional transfer link has been validated by the simulation and experimentalresults.6. To enlarge wireless power transfer distance via power relay nodes introducedinto the wireless power transfer networks and ensure wireless power transfer efficiencysynchronously, the novel concept of optimization mathematic model for wireless powertransfer link was proposed. The ant colony optimization has been modified by dynamicupdating mechanism of sociohormone to control prematurity convergence of thealgorithm and search among the feasible field effectively. The routing method ofwireless power transfer networks based on the refined ant colony optimizationalgorithm can construct power transfer route with the maximize power transferefficiency and high stability. Finally the simulation results have verified the advantagesof refined ant colony optimization used in the routing method of wireless power transfernetworks.The innovative contributions of this paper are:1. A novel concept of wireless power transfer networks based on wireless powertransfer technology has been proposed, through a series of power relay nodes a powertransfer route between the primary node and the pick-up node was constructed to finishpower multi-hop transfer process, some power transfer links can compose the wirelesspower transfer networks without a centre in networks, and with the peer to peer powertransfer nodes, in order to search after ensuring wireless power transfer efficiency andenlarging wireless power transfer distance synchronously. The multi power transfer linklife-span mathematic model and the network cover area evaluation model have been proposed.2. A basic circuit topology of wireless power transfer node with the functionality ofpower supply, power pick-up and power relay has been developed, at the same time, thecircuit topology of wireless power bi-directional transfer based on ICPT technology wasproposed. The circuit topology of wireless power bi-directional transfer link has beendemonstrated via mutual inductance coupled principle, it is derived that both the amountand direction of power flow between the primary node and the pick-up node can beregulated by controlling the relative phase angle between voltages generated by primarynode and pick-up node reversible rectifiers.3. To construct power transfer route with the maximize power transfer efficiencyand high stability a novel concept of optimization mathematic model for wireless powertransfer link was proposed, the refined ant colony optimization used in the routingmethod of wireless power transfer networks may build a wireless power transfer routethat can enlarge wireless power transfer distance and ensure wireless power transferefficiency synchronously.