Research On DWPT Technology Based On Three-phase Meander-type Magnetic Coupler

Rail transit exhibits better performances in efficiency,economy,and environment and has been playing a more and more important role in medium-and-long distance public transportation.The power supply of the current rail transit generally utilizes the overhead contact line or contact rail,which will cause mechanical wear and poor contact,and thus the system security and weatherability are poor.Usually,the contact line or contact rail is laid over the ground,resulting in safety risks,and will influence the urban landscape.To solve the above issues,dynamic wireless power transfer(DWPT)technology based on electromagnetic induction law has been proposed.Currently,the technical difficulties of the rail transit DWPT technology are mainly focused on the required large power and the high construction cost.On the one hand,the system feasibility and electromagnetic safety are aggravated by the high power.On the other hand,the application and popularization of the rail transit DWPT technology are limited due to the expensive cost.Currently,since the three-phase meander-type magnetic coupler shows excellent potential in high-power applicability,electromagnetic compatibility,and construction cost economy,this paper studies the magnetic coupler,circuit topology,and self-tuning control based on the three-phase meander-type magnetic coupler,aiming to improve the practicability of rail transit DWPT technology and to promote its industrial application.This paper is organized as follows.To meet the requirement of the large power in rail transit DWPT system,the three-phase meander-type magnetic coupler featured by high-power density is studied and designed in this paper.The characteristics of the magnetic coupler are investigated,and the parameter design method of the three-phase meander transmitting coil and the design scheme of the segmented connection structure of the transmitting coil are discussed.The influence mechanism of the receiving coil configuration and core utilization on the coupling performance is studied.Finally,The structure design method and scheme of high power density magnetic coupler with overlapped receiving coils and easy expansion are systematically summarized and proposed.Also,the corresponding design flow is given in detail.It is found that the power density is improved by 100% with the proposed method compared with the traditional configuration of the interval arrangement coil.For three-phase DWPT systems,the circuit topology and parameters design is studied on the basis of inductor/capacitor/capacitor-series(LCC-S)compensation topology to simplify the control of the transmitter.Thus the extra cost caused by the complicated control and the precise parameter configuration is eliminated.The characteristics of the LCC-S compensation topology in the three-phase DWPT system are analyzed,and the influence mechanism of the circuit topology type and parameters on the system performance is explored.Then the method of parameter measurement and compensation topology parameter configuration of the three-phase meander transmitting coil is put forward,and the feasibility of different circuit topologies of three-phase series compensation receiver is discussed.Additionally,the parameter design method considering the actual device parameter error and soft switching maintenance of the inverter is proposed in the view of the practical application,which improves the construction efficiency and reliability of the system.The self-tuning control strategy of the receiver,based on the synchronous PWM switched capacitor with the small volume and successi ve adjusting impedance,is studied to decrease the demand of the component accuracy and improve the system reliability.Based on the analysis of the reactance regulation characteristics of the synchronous PWM switched capacitor and the mistuning features o f the receiver in the three-phase meander-type DWPT system,the tuning feasibility of using the perturbation and observation(P&O)method to tune the three-phase receiver without additional detection coil and complex voltage and current detection and processing circuit is explored.Afterward,the three-phase cooperative tuning strategy is proposed by combined the phase difference control with the P&O method.The tuning speed of the proposed cooperative tuning method is about three times that of the traditional sequence tuning without using the additional hardware.For validation,a scaled-down prototype(1:5)of the three-phase meander-type DWPT system is designed and built,which is based on the same impedance characteristic as that of the practical rail transit.The correctness and feasibility of the theoretical analysis and the design flow are verified when compared the measured parameters with the designed values.The average power of 154W and the average efficiency of 90% is obtained for the rated output current when the receiver position is changed.In addition,the amplitude variation in the output voltage is maintained within ±3% for different positions.Furthermore,through specific cases and simulation analysis,the design method and process of thre e-phase LCC-S compensation topology parameters are verified when the device parameters have errors and the inverter soft-switching state maintenance and input current harmonic suppression are considered.Further,the actual experimental system is configure d according to the design results and tested to verify the effectiveness of the design and simulation analysis.Finally,a three-phase power receiver using synchronous PWM switched capacitor to realize self-tuning is built,and the effectiveness of the three-phase cooperative tuning control strategy based on phase difference control and P&O tuning method is verified by experiments.The results show that the self-tuning time of the proposed three-phase cooperative tuning control strategy can be reduced to 1/3 of that of the sequential tuning control strategy.