Research Of Magnetic Integration Technology In LCL Filter And Contactless Resonant Converter

With the fast development to high frequency,high power density and high reliability in power conversion technology,people have been puting forward higher requirements to magnetic technology.Magnetic integration technology is to make two or more discrete magnetic cores into one magnetic core,which can lower magnetic volume and improve the power density of power source device.There have been numbers of achievements during the development of magnetic integration technology for almost a century,and the booming new energy generation and contactless wireless power transfer technology will bring broader prospects to magnetic integration technology.Based on the two points mentioned above,this paper studies the magnetic integration technology.Firstly,the paper studied LCL filter in single phase inverter.Instead of the traditional magnetic integration method to integrate the two inductors in main power current loop,the paper proposes making the single inductor in main power current branch be coupled with the inductor extra added in the parallel branch,and a virtual inductor will be got in anothr main branch which can replace one inductor in main power current loop in traditional LCL filter.Theoretical analysis proves that the novel LCL filter based on coupled inductor can have the same filtering effect with traditional LCL filter and reduce the magnetic volume.The 1.2k W single-phase inverter prototypes are designed and builded based on traditional LCL filter and the novel magnetic integraion filter.The experimental results show that two filters have the same filtering effect and the proposed novel filter can reduce the magnetic volume.Then,the paper also studies the LCL contactless resonant converter based on integrated inductor.The paper makes the resonant inductor coupled with primary coil of contactless transformer to reduce the magnetic volume and the virtual capacitor generated by the magnetic integration can increase the value of resonant capacitance and reduce the voltage stress of resonant capacitor,which is benefit to the selection and reliable operation of capacitor.The paper,considering with the additional coupling effect after integration,detailedly analyses the influence of magnetic integration to LCL resonant converter in aspects of input impedance characteristic,voltage gain,input current harmonic characteristics and elements stress.The study shows that the additional coupling effect will change the input impedance angle in resonant frequency point and accordingly proposed an improved design method of compensation capacitor in second side.The theoretical analysis also shows that the magnetic integraion for the LCL resonant converter will increase the harmonic of the input current.At last,the paper build a 1k W experimental prototype,and the comparison results from the novel magnetic integraion LCL resonant converter and traditional LCL resonant converter verify the correctness of the theoretical analysis.The works of the paper show that magnetic integraion can effectively improve the characteristics of LCL filter and LCL contactless resonant converter.