Research On Control Strategy Of Three-phase Photovoltaic Grid-connected Inverter

With the problem of the environmental pollution and depletion of fossil fuel becoming moreand more serious, the development of renewable clean energy has become an inevitable trend.Research and practice have proved that the solar radiation energy-rich, no pollution andrenewable, has promising prospects for the development. Photovoltaic power generationbecomes main trend of the use of solar energy and the photovoltaic system, which turns intofocus of the study. The main research object is the grid-connected photovoltaic inverter, which isthe key equipment of photovoltaic power generation system. The control strategy of the inverteris in-depth discussed.First, the article describes the domestic and international research status and main controltechnology of grid-connected inverter. According to product demand, selection of neutral pointclamped three-level topology as the inverter main circuit structure, design the main circuit andcontrol circuit and simulation and experimental verification on the prototype circuit.Secondly, in order to study the three level pulse width modulation, the topological structureand working principle of neutral point clamped inverter circuit is analyzed. Also, two maincorresponding pulse width modulations are introduced: triangular carrier cascading method(SPWM) and space vector modulation method (SVPWM).Then an improved three-levelSVPWM simplified algorithm is proposed based on relationship between unified. The algorithmovercomes the shortcomings of traditional SVPWM algorithm with high complexity, largeamount of computation. This paper also analyzes the various neutral-point potential balancingcontrol strategy of the corresponding simplified algorithm.Then, the paper established a mathematical model of the neutral point clamped tube inverterunder the two-phase stationary coordinate system and the two-phase rotating coordinate systemand design current closed-loop PI controller of the grid-connected inverter. The paper also usestraditional methods and bacteria foraging algorithm tuning of the PI parameters respectively. Thedifference of bacterial foraging algorithm and genetic algorithm is compared.Finally, simplified SVPWM Algorithm, midpoint potential balance control strategy and PIcontroller are simulated by MATLAB/simulink. The simulation result is consistent with thetheoretical analysis, which verifies the feasibility and practicality of the design.