Research On Magnetic Integration For Interleaved-Flyback Photovoltaic Micro-inverter

Compared with traditional energy sources such as coal, oil and natural gas, solar energy has the advantages of unlimited reserves and little pollution, rational use of solar energy can effectively alleviate the current energy crisis. Solar power utilize the photovoltaic effect of the solar panel to convert solar energy into electrical energy, and the electrical energy is used for powering the device or delivered to the grid by the photovoltaic inverter. Contrast with the centralized and string-type photovoltaic architectures based on medium and large power level, the AC modular photovoltaic architecture based on micro-inverter that has strong anti-shading capability, plug and play, greatest power distribution and high utilization of photovoltaic panels has been one of important photovoltaic architectures.As one of the key devices of AC modular photovoltaic architecture, micro-power inverter has an important impact on the raise of system power efficiency and cost reduction. Considering factors such as cost and power level, currently the industry generally uses the interleaved-flyback inverter as the micro-inverter’s topology. The interleaved-flyback inverter, which is characterized by two flyback inverters parallel connected in the input and output side, not only increase the power level but also reduce the input and output current ripple.This paper proposed the application of the integrated magnetic technology on the interleaved-flyback inverter from the perspective of magnetic components. Compared with the discrete magnetic scheme, using the magnetic integration scheme can reduce the size of magnetic components, core loss and temperature rise, while reducing the current ripple of the primary and secondary side, so that it can meet the stringent requirements of the photovoltaic power density, efficiency and operating environment about micro-inverters.For the research on magnetic integration for interleaved-flyback photovoltaic micro-inverter, firstly this paper analysis the key waveform and different stages’ operating mode on the basis of discrete magnetic scheme and derive the control strategy of grid current. Secondly, this paper proposes the decoupling and coupling magnetic integration scheme base on the interleaved-flyback inverter’s high-frequency transformer. Combined with the circuit and magnetic principles, the effects of core size, core losses and current ripple of primary and secondary side for the two magnetic integration schemes is researched. Thirdly, the simulation models of grid current control strategy and two magnetic integration schemes is built base on the SABER, the simulation results verify the feasibility of the current control strategy and magnetic integration schemes. Finally, a prototype of discrete magnetic scheme and a prototype of integrated magnetic scheme are designed. The experimental results of the prototypes’ test draw the conclusion that the magnetic integration scheme can effectively reduce the size of magnetic components and the current ripple of the primary and secondary side, while improving the overall efficiency of the inverter, so that it verify the feasibility and effectiveness of the magnetic integration scheme.