Research On Planar Magnetic Integration For Interleaved-flyback Photovoltaic Micro-inverter

Solar energy plays an important role in the development and utilization of new energy,which has the advantages of large reserves,non-pollution and wide application area.Grid interactive PV is an important way of utilizing solar energy.The AC-Module has been widely used for its strong anti-shadow,plug and play,and high utilization of photovoltaic(PV)panels.Photovoltaic micro-inverter(PVMI)is a key apparatus of AC-Module PV power generation system.Considering the factors of cost and power level,the interleaved flyback circuit connected with power frequency polarity reversed Bridge is adopted as the main circuit of the power grid connected inverter.The interleaved flyback circuit with two channels of flyback converter can not only improve the power level of the inverter,but also reduce the current ripple of the input and output side.For the stringent requirements of power density,efficiency and operating environment of PVMI,planar magnetic integration is used to the interleaved-flyback PVMI.Reasonable application of magnetic integration technology can reduce the size of the magnetic components,reduce the loss of core and windings,and improve the current ripple of the input and output side.At the same time,the planarizartion of the magnetic core and windings has excellent characteristics of small size,large surface area,easy heat dissipation,good consistency of the parameters and small leakage inductance.Firstly,this paper analyzes the working principle of the interleaved-flyback PVMI,and derive the expression of the grid current control strategy.Secondly,this paper compares and analyzes the different magnetic integration schemes,mainly analyzes the influence of the reverse-coupling magnetic integration scheme on the steady-state current ripple of single flyback.Meanwhile,based on the Saber simulation software,the simulation model of the discrete magnetic parts,the reverse-coupling magnetic integration scheme and the grid control strategy is build to verify practicability.Thirdly,the influence of different winding layout schemes on the leakage inductance and winding loss of the transformer is compared and analyzed,and each scheme is simulated by finite element software Maxwell 2D.Meanwhile,the effect of winding edge effect and air gap flux is analyzed.The model of the planar transformer which built in the PExprt software is imported to the simulation model of the main circuit built in Simplorer software.This simulation combining with control circuit model built in Matlab software verifies practicability of the planar transformer model.Finally,a 220W interleaved-flyback PVMI prototype with dsPIC33FJ32GS606 controller is designed.Experiment results are provided to verify planar magnetic integrated scheme can effectively improve the primary and secondary current ripple and improve efficiency of the inverter.That is the planar magnetic integrated scheme is feasible and effective.