Research On Dynamic Wireless Power Transfer System With Multi-parallel Transmitters

Traditionally,the vehicles are powered by internal combustion engines.Though these engines can provide high power and great cruising ability,they suffer from the drawbacks in low energy conversion efficiency and harmful gas emission.By contrast,electric vehicles,powered either solely by car battery or car battery as well as supercapacitor are not only environmentally friendly,low in noise generation and flexible in control,but also can exchange power with the grid bi-directionally,which contributes to regulating the power at night.All these aforementioned factors make the EVs one of the most potential vehicles for the future.However,the electric vehicles are still hampered from large-scale commercialization by the electricity storage technology.Lithium-ion batteries are recognized as the most competitive solution to be used in electric vehicles.The commercialized lithium-ion battery in EVs are still unsatisfying considering its energy density,life span and the cost.Besides,other challenges like the long charging time of EV batteries,mechanical wearing and aging leakage of the charger also lead to the less popularity among consumers.Dynamic charging is a promising technology that can help promote the adoption of EVs.When the vehicle is moving on the roadway,it can be continuously powered.The driving range of the EV can be extended,and a smaller battery pack can be used in order to reduce the vehicle weight and improve transportation efficiency.For the past years,the dynamic wireless power transfer technology is attracting increasingly attention both at home and abroad.Dynamic charging systems can be classified according to the length of their transmitter coils: i.e.,either long-track-loop transmitters or short-individual transmitters.However,the long-track-loop type suffers from the low-efficiency and high sensitivity to the parameter variation.To address that challenge,this paper proposes a dynamic wireless charging system with multi-parallel transmitters,which are fed by a single full bridge inverter.The LCC compensation network is adopted which is famous for its impedance transformation characteristic and insensitivity to the parameters deviation.The LCC compensation network can transform the square wave voltage source into a sinusoidal current source which is irrelevant to the misalignment and load variation,rendering a constant current flowing in the transmitters.Besides,considering the power null phenomenon existing in one receiver system,a structure with two receivers in parallel is utilized,which turns out to be effective in reducing power pulsation and cancelling the power null point.Specifically,in this paper,dominating factors that influence the efficiency of power transfer and capability of output power is analyzed based on the mutual inductance model and the method to design parameters is derived;Through finite elements method,the mechanical structure of the loosely coupled transformer is simulated and optimized to maximize the coupling between the transmitter and the receiver;moreover,the influence of the high-order harmonics incurred by both inverters and rectifiers is discussed.A prototype is designed and built to test the analysis.Within the designed distance,the average output current is 9.3A which is close to the designed value,and the efficiency peaks at 81%.By comparing the waveforms of the system,it is found that the experimental results match well with the theoretical analysis.