Research Of Micro-inverter And MPPT In Photovoltaic Power Generation System

Today, the whole society is being inevitably faced with increasingly energy andecological crisis due to human’s overexploitation and use of non-renewable energy.On the contrary, solar energy is safe, reliable, noise-free, pollution-free andinexhaustible. Therefore, with the rapid development of PV market and the highefficiency of power electronic devices, solar energy will become an important partthat can not be replaced in new energy. However, in order to effectively use solarenergy, a power converter is needed, and micro-inverter becomes to be the new choicebecause of its small size, high efficiency, ease of integration, convenience ofexpansion and so on. In addition, in order to use more efficiently, it’s necessary totimely follow the maximum power point. So, the study of micro-inverter and MPPT inPV power generation system is of great practical significance and research value.After combining the existing micro-inverter with the characteristics ofBuck-Boost circuit, this paper put forward a new dual Buck-Boost topology, andelaborated the working principle and working modals in terms of energy’s two-waytransmission. Then, in order to avoid the weak points of PID control, a simple andreliable double-loop control strategy was proposed on the basis of studying thelarge-signal model of Buck-Boost circuit. At last, simulation was carried on to analyzethe system’s resistance to input voltage changes and load changes, and simulationresults showed the correctness, rationality and feasibility of the method.Finally, combining the power-tracking curve of the PV panel with the existingMPPT methods, this paper made some improvements to incremental conductancemethod with a result that a multistage variable step method is proposed, and then builtits simulation model in MATLAB/Simulink environment. Through simulationanalysis, the method always could make PV panel work at the maximum power point,whether the environment changed slowly or suddenly, which effectively resolved thecontradiction between tracking speed and control accuracy. At last, simulation resultsverified the correctness, feasibility and superiority of the algorithm.