| The consumption of the non-renewable energy is greatly increased as the development of theworld’s economy. And the storage of the non-renewable is decreasing dramatically. In order tosolve the energy crisis, the researchers are making efforts to develop some clean energy tosubstitute the conventional fossil energy. In recent years, people pay more and more attention onsolar energy. And the investment on solar energy continues to grow vastly. Distribution is one ofthe most competitive advantages of grid-connected photovoltaic. The redundant electricity canfeedback to the grid. Among the system, the micro-inverter is the most important equipment.The electrical characteristics of the micro-inverter contain the follows:(1)The input voltage of the micro-inverter, about16~50V, is relatively low.(2)The output voltage of the micro-inverter is relatively high, and the output power is about300W.(3)The requirement on efficiency of the micro-inverter is high, and the maximum efficientneed above95%.(4)The micro-inverter need a long lifetime, the warranty time is about25years.(5)Small dimension is preferred to integrity with the PV panel.There are many ways to classify the topology of micro-inverter. According to the type of thetransformer in micro-inverter topology, the topologies of the micro-inverter can be classified intothree types: non-transformer type, low frequency transformer type and high frequency transformertype. The drawback of the topology without any transformer is obvious. The common-modeleakage current may cause some security problem because of the non-isolated topology. Thedimension of the low frequency transformer is larger. And the LFT will cause efficiency decline.The settlement solution containing HFT is widely adopted in commercial micro-inverter becauseof the high efficiency and small dimension of HFT.The micro-inverter designed in this paper also adopted the flyback topology. First, make abrief introduction of micro-inverter’s background. Then, make a simulation of the single PV panelto learn about the characteristic of the PV panel. After that, the operation principle of the proposedmicro-inverter is analyzed. Then, the hardware and software of the control circuits is analyzed.And a brief introduction of the control IC is presented. Finally, a200W prototype is built to verifythe theoretical analysis. |
