Photovoltaic String Electrical Model Determination With Derivation Effects
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Solution Overview
Problem
Current methods for diagnosing chains of photovoltaic modules are not robust to measurement noise and cannot accurately determine the electrical model parameters, especially in the presence of derivation effects such as partial shading, requiring assumptions about environmental conditions and lacking on-site applicability.
Innovation Solution
A method that detects first and second linear zones in the I(V) characteristic, initializes and optimizes parameters for an electrical model without derivation, and determines the best model with or without bypass diodes, allowing for robust on-site diagnostics without environmental measurement assumptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If derivative effects (partial shading, bypass diodes) are present in the photovoltaic chain, then the I(V) curve becomes more complex with inflections, but existing diagnostic methods cannot accurately determine electrical model parameters under these conditions
Solution Approach 1:
The patent segments the I(V) curve into multiple zones (first linear zone, second linear zone, and intermediate zone) to separately analyze different operational conditions. By dividing the curve analysis into distinct segments, the method can identify derivation effects in specific zones while maintaining accurate parameter determination in other zones, resolving the contradiction between handling complex derivation conditions and maintaining measurement precision.
Solution Approach 2:
The patent performs preliminary detection of linear zones and identification of derivation effects before proceeding with electrical model parameter determination. This preliminary analysis allows the method to adapt its parameter estimation approach based on the detected conditions, ensuring accurate results whether derivation effects are present or absent, thus improving both precision and adaptability.
2Ease of operation
If existing diagnostic methods are used on-site, then environmental measurements and assumptions are required, but this increases device complexity and reduces ease of operation
Solution Approach 1:
The patent enables the diagnostic system to determine electrical model parameters using only the I(V) curve data from the photovoltaic chain itself, without requiring external environmental measurements or assumptions. The method extracts all necessary information from the I(V) characteristic, allowing on-site diagnostics to be performed with minimal equipment, thus improving ease of operation while reducing device complexity.
3Reliability
If derivative effects are present, then bypass diodes make parts of the chain independent, but this prevents existing methods from diagnosing the entire chain effectively
Solution Approach 1:
The patent segments the photovoltaic chain into affected and unaffected portions based on I(V) curve analysis. By identifying which segments are influenced by derivation effects (through detection of linear zones and inflection points), the method can diagnose each segment appropriately and aggregate the results to provide complete chain diagnosis, maintaining reliability despite the chain being divided into independent parts by bypass diodes.
Data Source
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AI summary
One aspect of the invention relates to a method (100) for determining an electrical model of a string of photovoltaic modules from a characteristic I(V) of said string comprising: a step (E2) of detecting a first linear zone and a second linear zone of the characteristic I(V); a step (E3) of initializing the parameters of a non-derivative electrical model corresponding to a first operating condition, called the non-derivative condition; a step (E4) of optimizing the parameters of the non-derivative electrical model from a reference characteristic I(Vref) equal to I(V); a step (E5) of determining the parameters of the electrical model corresponding to a second operating condition, called the condition with derivation, in order to obtain a derivative electrical model from the characteristic I(V);a step (E6) of determining, from the characteristic I(V), the best model among the model without derivation and the model with derivation.;