Brand-new photovoltaic grid-connected inverter multi-wave-crest MPPT algorithm

Abstract

The invention discloses a brand-new photovoltaic grid-connected inverter multi-wave-crest MPPT algorithm. The brand-new photovoltaic grid-connected inverter multi-wave-crest MPPT algorithm includes determination of a working voltage meeting formula of a photovoltaic system, determination of a shadow judgment formula and shadow scanning and comprises the specific steps of firstly determining the working voltage meeting formula of the photovoltaic system, determining the shadow judgment formula according to the determined working voltage meeting formula of the photovoltaic system after the working voltage meeting formula of the photovoltaic system is determined, and performing shadow scanning after the judgment formula is determined. When a local shadow is produced, a local best working point is possibly located on the right side or the left side of the best working point in the last minute, but it is unknown whether a current working point is the best working point of the system or not at the moment, scanning is required to be performed again, other local best working points are found out and compared, and then the position of the highest one of the powers of the best working points found out in the comparison process is the best working point of the system.

Description

technical field [0001] The invention relates to an inverter multi-peak MPPT algorithm, specifically a brand-new photovoltaic grid-connected inverter multi-peak MPPT algorithm, which belongs to the application technical fields of computer network, graphics and image processing, computer performance improvement, encryption and decryption, and Chinese character input. . Background technique [0002] Every photovoltaic power generation system has a PU curve, which is a parabolic function P=f(U), which means that each voltage corresponds to a unique power value. As the control center of the photovoltaic system, the photovoltaic grid-connected inverter One of the main functions of the inverter is to control the working voltage U of the photovoltaic system at a reasonable value Umax, so that the output power P of the system is at the maximum output point Pmax. However, in actual use, due to shadow occlusion and other reasons, the PU curve of the original system will produce two or...

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Problems solved by technology

[0003] At present, with the gradual popularization of domestic distributed photovoltaic systems, some local shadow problems will inevitably appear in reality, such as fallen leaves, light poles, trees, parapets, etc., so in order to better face such problems, we can To minimize the loss, it is necessary to have a completely different algorithm that can greatly improve the efficiency of MPPT in the case of partial shadows. Based on the actual application characteristics, it is necessary to greatly improve the software calculation for judging whether the maximum value of the current operating point is the maximum value of the system. Efficiency. In most cases, the photovoltaic system itself does not have shadow problems. If it is compatible with shadow tracking, the system without shadow occlusion must be forced from the maximum value of the system to zero every once in a while, and then it will take a while to restart. In the process from zero to maximum voltage, this will bring additional power loss, causing the normal system to lose power every once in a while, and the accumulation is not a small number

The reason for this situation is that the fixed-period scanning method does not realize the judgment of whether there is shadow or no shadow, but only realizes the problem that the system avoids falling into the local maximum operating point within a certain period of time.

In addition, when shadows occur, the shadows are not static. When the shadows change, the photovoltaic system tracking also needs to follow up the changes. The photovoltaic system may switch between partial shadows and no shading at all. In the east, the photovoltaic system will have partial shadow problems in the morning, but in the afternoon, the photovoltaic system will be completely unblocked, so the full-cycle scanning method cannot perform this state conversion, so it cannot meet the actual application. When the shadow occurs , the full-cycle scanning method also has very big defects. The full-cycle scanning method is passive and cannot achieve real-time performance. It can only realize actions within a certain period of time after the shadow occurs, rather than immediately. At the same time, when When it starts to act, it takes a long time. The entire scanning range covers from zero to the maximum voltage of the system. The scanning range is large, without optimization, and the algorithm is relatively simple, so whether it is from the change of shadow conditions, the real-time response of the system or the optimization of the scanning range On the one hand, the original full-cycle scanning method cannot meet the application of the actual situation. Therefore, a new multi-peak MPPT algorithm for photovoltaic grid-connected inverters is proposed to solve the above problems.

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