Research On Energy Modeling And Application Forwireless Power Transfer System

Inductive Coupled Power Transfer (ICPT) is a novel techonology developed todeliver power contactlessly from power supply to one or more movable loads. It isbased on electromagnetic coupling theory and involving modern power electronics,control theory and magnetic coupling techniques. The main advantages of thistechnology are safe, flexible, easy to maintain, highly reliable and environmentallyfriendly.In ICPT system, due to loosely coupled characteristic between primary side andsecondary side, resonant mode will be adopted to improve efficiency and level of powertransfer. According to different demands of loads, different reactive powercompensation circuit topologies and control mode will be adopted. Any tinny changecaused by operating state and system parameter will lead to great changes in systemmodel if traditional modeling approaches be adopted, it is very inconvenient fordesigners that the system model have to be restructured. ICPT system is a typicalnonlinear, high-frequency, multi-parameters system and there are strong adhesionbetween different parameters. Control behaviors in different functional modules must behighly unified the overall system control mode. While the system model established bytraditional modeling approaches and control mode just adapt special system, lackinggenerality. So, poor compatibility and low portability between different modules isgreatly limits the development of ICPT tehnology.In view of the above questions, the paper proposed energy modeling and relevantcontrol strategy just like reflection impedance identification, frequency stability control,output power control and so on, which was aimed at solving general modeling approachand control mode for ICPT system.The main works of the paper include:1. Aimed at the defects that traditional system modeling depends on specific circuittopology and operating state in ICPT system, the paper analysed the demands ofmodeling and control in every key part in ICPT system, proposed a energy modelingapproach based on law of conservation of energy. In this modeling approach, ICPTsystem was divided by several energy flow key points according to different fuctionmodules, loss and direction in every energy flow key point was analysed; energy inputand output formule was established; energy model of electrical energy transformer, reactive power compensation circuit and electromagnetic coupling mechanism wereestablished, the system model and schematic diagram was presented.2. Aimed at loads in ICPT system are difficult to detected and identified caused bycharacteristic of high-order, non-linear and electric isolation, from the point of view ofenergy, established the ICPT system energy model. Analysed series-parallel reactivepower compensation circuit topology, a load identification approach suitable for anytopology in ICPT system was proposed, control flow and computational formula werealso presented. The theoretical analysis was verified according to simulation andexperiment results.3. Aimed at low efficiency and level of power transfer caused by resonancefrequency drifting because of uncertainly loads, a criterion of system operating state andself tuning control strategy based on energy model was proposed, the criterion andcontrol strategy is suitable for any ICPT system. TS reactive power compensationcircuit was made an example and theoretical analysis was verified according tosimulation and experiment results.4. Aimed at loads in ICPT system are difficult to detected and identified caused bycharacteristic of high-order, non-linear and electric isolation, the paper separatelyproposed ICPT system output power control strategy by energy injection and pick-upcircuit periodic energy injection output power control strategy based on loads demands.The design of control strategy and establish of system model according to therelationships of energy flow between input and output, to adapt any reactive powercompensation circuit topologies in ICPT system. Concept of power regulation duty ratiowas proposed, computational formulas was presented. Simulation and experimentresults verified the theoretical analysis.The innovative contributions of this paper are:1. Aimed at ICPT system is difficult to modeling and solve caused by variedreactive power compensation circuit topologies, the paper proposed the concept ofenergy flow key points in ICPT system, according to the relationships between energyinput and output in every key point, a modeling approach based on energy conservationsuitable for any reactive power compensation circuit in ICPT system was proposed.Compared to traditional modeling approaches, the modeling process based on energyconservation was greatly simplified. This modeling approach also could be used inenergy conversion system.2. Aimed at loads in ICPT system are difficult to detected and identified caused by characteristic of high-order, non-linear and electric isolation, a load identificationapproach suitable for any topology in ICPT system was proposed, control flow andcomputational formula were also presented.3. Aimed at low efficiency and level of power transfer caused by resonancefrequency drifting because of uncertainly loads, a criterion of system operating state andself tuning control strategy based on energy flow direction was proposed, the criterionand control strategy is suitable for any ICPT system.