Research On Control Strategy And Output Characteristics Of Wireless Charging Secondary Side Of Electric Vehicle

With the wide application of electric vehicles,the battery life has become the key to affecting electric vehicles,the charging method of electric vehicles has also become a hot spot for scholars at home and abroad.The wireless charging technology has the advantages of safe and reliable charging,convenient carrying,light weight,and small switch wear,it has been researched and applied in new energy vehicles by many scholars at home and abroad,opening up new avenues for improving the endurance of electric vehicles.The main work of this paper is based on inductively coupled radio energy transmission technology,combined with compensation network output and DC-DC circuit using sliding mode control,so that the output remains stable;The loosely coupled transformer is optimized to improve its transmission efficiency.Specifically,the research is carried out from the following aspects:Firstly,the background meaning of radio energy transmission and the research status at home and abroad are introduced,the transmission mode of radio energy transmission and the charging mode of electric vehicle wireless charging are introduced in detail,and the key points affecting the wireless charging of electric vehicles are analyzed.Secondly,the four basic compensation topologies commonly used in wireless charging and other hybrid compensation topologies based on this are introduced,the output characteristics of three compensation topologies of SS,SP and SSP under different operating conditions are compared in detail,and the SSP topology is more suitable.Electric vehicle wireless charging,determine the main circuit adopts SSP compensation topology;The relationship between output energy efficiency and mutual inductance and resonant frequency of SSP compensation topology is further deduced,and the influence of parameter variation on output energy efficiency characteristics is analyzd;the simulation verifies that SSP has constant voltage output characteristics under different load conditions.Again,establish an equivalent model for the battery and analyze its charging method;Deriving the relationship between the SSP compensation topology output and the Buck-Boost circuit duty cycle,determining the adjustment duty cycle can change the SSP output;Aiming at the problem that the large output of the loosely coupled transformer is easily affected by the distance disturbance,the sliding mode control is adopted for the Buck-Boost circuit,so that the Buck-Boost circuit can stabilize the output when the output of the loosely coupled transformer is disturbed;The simulation verifies that the steady-state constant-voltage stable output can be realized by sliding mode control.Then,according to the core structure and winding mode of the existing planar U-shaped transformer,it is optimized and improved to improve the coupling coefficient of the loose coupling transformer;The coupling coefficient of three kinds of transformers is quantitatively analyzed.The theory and simulation analyze the variation law of the coupling coefficient when the relative position of the primary and secondary coils changes;it is concluded that the magnetic coupling ability of the loosely coupled transformer after adding the core is enhanced,which can improve the output energy efficiency.On the basis of this,the auxiliary winding and the secondary winding are added together to improve the output energy efficiency when the lateral position of the coil changes,and the simulation is consistent with the theory.Finally,the experiment proves that the addition of sliding mode control can achieve stable output voltage and current when the relative position of the loosely coupled transformer changes;On the basis of the plane U-shaped,the transformer structure is improved,the output of the two transformers is compared,and the auxiliary winding is wound,and the output characteristics when the relative position of the coil changes are analyzed.It is experimentally verified that the new loosely coupled transformer with the magnetic core can improve the output energy efficiency.