Method and device for maximum power tracking of photovoltaic cell modules based on knee point equal power method

Abstract

The invention discloses a photovoltaic cell pack maximum power tracking method and device based on a knee point equipower method. Due to the fact that in an actual photovoltaic power generation system with photovoltaic assemblies connected in series, when multiple photovoltaic cells are blocked or blocked to different degrees, a plurality of knee points can appear in the I-U characteristic curve of a whole photovoltaic array, a plurality of peak points can appear in a corresponding P-U characteristic curve, a multi-peak-value curve characteristic is achieved, and a traditional maximum power tracking algorithm is likely to lose efficacy. Through the relation of the voltages of all the knee points and the peak points of power curves, the maximum power tracking algorithm with a constant voltage tracking method and a disturbance observation method combined is adopted, the maximum power points, blocked by shadows, of a series-connection photovoltaic cell pack can be accurately tracked better, and energy losses caused by overlong-time non-maximum power point area search can be eliminated.

Description

technical field [0001] The invention relates to the technical field of solar photovoltaic power generation, and more specifically, to a method and device for tracking the maximum power of photovoltaic cell components based on the knee-point equal power method. Background technique [0002] In actual photovoltaic system applications, the installation and application environment of photovoltaic modules seriously restrict the conversion efficiency of photovoltaic modules, especially the problem of photovoltaic shadow shading seriously affects the conversion efficiency and reliability of photovoltaic modules. As the environment of photovoltaic power generation systems becomes more and more complex, especially in areas with relatively dense buildings, or limited by the appearance of photovoltaic arrays, it may not be possible to ensure that sunlight is not blocked throughout the day, resulting in the generation of photovoltaic arrays. Partial shadows, or even full-sky occlusion i...

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Problems solved by technology

[0004] (1) Two-step method, control the operating point of the photovoltaic array near the maximum power point from the equivalent load of I-U, and then use the single-peak MPPT algorithm to complete the maximum power tracking. This method has the problem of misjudgment, and it is likely to find The minimum value point, the accuracy is not high;

[0005] (2) The global scanning method scans the voltage and power of each peak point, and then determines the maximum power point. Although this method can accurately search for the maximum power point, too long non-maximum power point area search will cause corresponding energy loss;

[0006] (3) The improved fixed voltage proportional scanning method is similar to the global scanning method, except that the voltage step adopts the working voltage of one of the n molecules closest to a peak point at the open circuit voltage value, and the voltage step of this method will vary with the peak value. The voltage change at the point, there is a possibility of missing the maximum power point

However, the number of fish schools, that is, the number of iterations n, will directly affect the number of search times in the non-maximum power point area. Too long search times will cause corresponding energy loss, and too short global search will lead to a decrease in the accuracy of the peak point.

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