PV String Curve Scanning for Light-Change Detection
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Solution Overview
Problem
Existing photovoltaic power generation systems face challenges in accurately determining the integrity and power generation capability of photovoltaic strings due to the influence of light changes during IV curve scanning, leading to unreliable results.
Innovation Solution
A parametric curve scanning method is employed, involving separate voltage range scans with overlapping endpoints to compare current parameters at the same voltage points, allowing for the detection of light-induced changes and ensuring the validity of the scanned curves without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IV curve scanning is performed on the photovoltaic string to detect defects and determine power generation capability, then measurement information is obtained, but light changes during scanning cause the IV curve to inaccurately reflect the photovoltaic string's output features
Solution Approach 1:
The patent performs IV curve scanning twice: first in a normal state to obtain an initial IV curve, and then after a light change to obtain a second IV curve. By periodically repeating the scanning process under different lighting conditions, the system can compare the two curves to determine whether light changes have affected the photovoltaic string's performance, thereby improving measurement reliability
Solution Approach 2:
The system uses the comparison result between the first and second IV curves as feedback to determine whether the photovoltaic string is defective. If the curves differ beyond a threshold, it indicates a defect; otherwise, the string is functioning normally. This feedback mechanism enables accurate defect detection while accounting for light changes
2Reliability
If additional hardware devices are added to improve scanning reliability, then measurement accuracy improves, but device complexity and costs increase
Solution Approach 1:
The system uses its existing scanning capability to perform self-diagnosis by comparing IV curves obtained under different lighting conditions. No external reference equipment or additional sensors are needed - the photovoltaic string scans itself twice and the controller compares the results. This self-service approach improves reliability without increasing hardware complexity
Solution Approach 2:
The patent creates a copy of the IV curve measurement process by performing the scan twice - once before light change and once after. This temporal copy allows comparison to detect light-induced variations without requiring parallel measurement systems or additional hardware, maintaining simplicity while improving reliability
Data Source
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AI summary
This application relates to a converter in a photovoltaic power generation system and a parametric curve scanning method for a photovoltaic string. A parametric curve includes a current-voltage curve or a power-voltage curve. The scanning method includes: controlling an output voltage of the photovoltaic string to change from a first endpoint voltage of a first voltage range to a second endpoint voltage of the first voltage range according to a first preset rule, to scan a first parametric curve; controlling the output voltage of the photovoltaic string to change from a third endpoint voltage of a second voltage range to a fourth endpoint voltage of the second voltage range according to a second preset rule, to scan a second parametric curve. There is an intersection set between the first voltage range and the second voltage range. In this application, whether a scanned curve is affected by a light change may be determined based on the first parametric curve and the second parametric curve. This is convenient and fast, and no additional hardware test device is required.