Research On WPT Systems Based On Interleaved Boost Converter And Flat Solenoid Coupler

Wireless power transfer technology can transmit energy without using metal media.It has the advantages of high flexibility,safety,and convenience,which has been extensively studied by scholars.In the process of WPT technology becoming practical,there are mainly two major problems.Firstly,the misalignment between the primary side and secondary side of loosely coupled transformer will cause the output performance of the system to deteriorate.Hence,the difficulty of closed-loop control of the system will increase.Secondly,loosely coupled transformers are relatively large in size and cost,which is not conducive to industrial development.Under the above background,this thesis proposes a WPT system based on interleaved Boost converter and flat solenoid coupler,and conducts in-depth research on magnetic coupling structure(MCS),converter,and closed-loop control method.There are many types of MCSs,but the misalignment tolerance needs to be improved,and the cost and weight need to be reduced.This thesis firstly explains the reason for the strong misalignment tolerance of the flat solenoid coupler according to the magnetic field distribution of the MCS before and after misalignment.What’s more,this thesis adopts the controlled variable method to study the structure of flat solenoid coupler in order to improve the misalignment tolerance of the system.The ferrite cores of primary side and secondary side of flat solenoid coupler are removed,and the ratio of the removal of the primary side and secondary side is studied to reduce the cost and weight of the system.What’s more,this thesis studies the winding pitch of the flat solenoid coupler to improve the misalignment tolerance of the system in the direction of the magnetic field.After optimization,this thesis obtains a split flat solenoid coupler with the best misalignment tolerance and lower cost.The miniaturization of the secondary side is a trend in the development of WPT systems,and the loss of the system is mainly concentrated on the primary side.In order to reduce the number of system stages,increase the voltage of the DC bus,reduce the current of the primary side and improve the power transfer efficiency,this thesis introduces the interleaved Boost converter on the primary side.The output gain,power transfer efficiency improvement strategy,and parameter sensitivity of the WPT system are studied in this thesis based on the characteristics of the interleaved Boost converter.Then,the parameters of primary and secondary self-inductance are designed according to the stress of the passive components in order to lay a theoretical foundation for subsequent experiments.When the misalignment between the primary side and secondary side of MCS takes place,this thesis adopts the closed-loop control of primary side and secondary side to stabilize the output voltage.The sampled value of the secondary side is sent to the primary side through the Bluetooth module,and the duty cycle of the interleaved Boost converter is controlled.This thesis adopts DSP processor to write sampling and communication programs.At the same time,the GSSA method is used to model the proposed WPT system.The Bode plot of the system is obtained,which is compared with the circuit sweep curve,and the accuracy of the modeling and the causes of errors are analyzed to verify the rationality of the model establishment.Finally,this thesis builds a WPT system prototype with an output power of 500 W based on the previous theoretical analysis.The power transfer distance of the primary side and secondary side is 170 mm.The output voltage of the prototype keeps constant when the misalignment is 200 mm in the horizontal direction or 100 mm in the vertical direction.The power transfer efficiency can reach to 90.1 %.