Title:	Precise On-Site Power Analysis of Photovoltaic Arrays by Self-Reference Algorithm
Author(s):	M. Scheler, D. Daume, D. Sojitra, T. Neumeyer, S. Steinbach, T. Beck, A. Schulze, B. Hüttl
Keywords:	Environmental Effect, Evaluation, Performance, PV Array, Experimental Methods
Topic:	PV Systems Engineering, Integrated/Applied PV
Subtopic:	Operation, Performance and Maintenance of PV Systems
Event:	8th World Conference on Photovoltaic Energy Conversion
Session:	4DO.1.4
Pages:	1070 - 1073
ISBN:	3-936338-86-8
Paper DOI:	10.4229/WCPEC-82022-4DO.1.4
Price:	0,00 EUR
Document(s):	paper, presentation

Abstract/Summary:

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To detect degradation of photovoltaic systems at an early stage, precise performance determinations are essential. Current-voltage measurements on single modules in indoor labs under well-defined conditions are state-ofthe-art. However, this method causes a logistical and economic effort. On-site measurements reduce the effort but are prone to error because of poorly determinable test conditions: The detected temperature on the backside of modules as well as the irradiance detected by pyranometer in tilted module plane usually differs from the actual operating conditions. In consequence, the accuracy of measured current-voltage characteristics is poor. A precise on-site power determination is achieved by a self-reference algorithm. Improvements by self-referencing are not achieved by correcting the raw electrical data, but by replacing the measured test conditions (temperature and irradiance) with effective data. These effective values correspond better to the actual module irradiance and temperature values. Furthermore, precise power determination of photovoltaic arrays requires to identify and exclude temporarily deformed current-voltage curves from consideration, as it can arise from non-uniform irradiation within array like shading. In this paper, the application of a digital curve filter is reported and performance determinations by a self-reference algorithm are demonstrated on a photovoltaic array. We review and discuss the measurement concept in terms of its ease of use.