Controller And Hardware Design Of PV Grid-Connected Micro-inverter

With the increasing depletion of traditional fossil energy on the earth, human beings are eager for new energy sources to replace. Solar energy is widely favored by the energy industry because of its high efficiency and clean without pollution, so photovoltaic power generation gradually became popular. Inverters usually play an important role in the field of photovoltaic power generation. In addition, due to the gradual popularization of distributed photovoltaic power generation in recent years.Therefore many higher requests are put forward to the inverters. Due to the features of its small size, flexibility, easy to install, high efficiency, and can be directly integrated into a single module with independent photovoltaic panel battery, so the micro-inverter is gradually applied to distributed generation. Based on such a development background,so this paper will research on the micro-inverters.Firstly, by comparing the traditional flyback and double way interleaved parallel flyback topology, highlight the characteristics of double way interleaved parallel flyback that can reduce the input current ripple and output current THD. So this paper adopted a double way interleaved flyback topology based on discontinuous mode, then verified the feasibility and effectiveness of the proposed model, by building Matlab system simulation.Secondly, researched on the control strategy of micro-inverter grid-connected inductor current emphatically. For PI in tracking AC signal can not completely eliminate the steady-state error and PR easily affected by the frequency fluctuations of the power grid and other defects. So proposed an adaptive PR controller, based on a "mountain climbing" band pass filter. At last, the system simulation results show that the adaptive PR controller can ensure the quality of the current and the tracking performance when the frequency fluctuation of the grid.Thirdly, designed the partial hardware circuit of the system in detail, and based on the hardware design, calculated the loss, established the mathematical model of the loss,analyzed the influence of current and frequency on the loss by simulation, finally selected the same current and the frequency of operation mode to reduce the system loss.Fourthly, developed a prototype of micro-inverter with a rated power 250 W, and verified effectively the key waveforms of the system and the control strategy. The experimental results show that the designed controller has better control effect.