Masking of photovoltaic system performance problems by inverter clipping and other design and operational practices. (July 2021)

• Record Type: Journal Article
• Authors: Balfour, John; Hill, Roger; Walker, Andy; Robinson, Gerald; Gunda, Thushara; Desai, Jal
• Is Part Of: Renewable & sustainable energy reviews. Volume 145(2021)
• Publication Date: 2021-07
• Subjects: Photovoltaic system performance -- Operation and maintenance (O&M) -- Masking -- AC/DC ratio -- Inverter saturation -- Inverter clipping -- Availability -- Performance ratio; Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.rser.2021.111067
• Languages: English
• ISSNs: 1364-0321

Abstract

Abstract: This paper describes how performance problems can be "masked, " or not readily evident by several causes: by photovoltaic (PV) system configuration (such as the size of the PV array capacity relative to the size of the inverter and the resultant clipped operating mode); by instrumentation design, installation, and maintenance (such as a misaligned or dirty pyranometer); by contract clauses (when operational availability is transformed to contractual availability, which excludes many factors); and by identified management and operational practices (such as reporting on a portfolio of plants rather than individually). A simple method based on a duration curve is introduced to overcome shortcomings of Performance Ratio based on nameplate capacity and Performance Index based on hourly simulation when quantifying masking effects, and inverter clipping and pyranometer soiling are presented as two examples of the new method. With a better understanding of the non-transparency of masking issues, stakeholders can better interpret performance data and deliver improved AC and DC plant conditions through PV system operation and maintenance (O&M) for improved performance, reduced O&M costs, and a more consistently delivered, and reduced, levelized cost of energy (LCOE). Highlights: Consider "masking, " or hiding of performance problems by design and operational practices when interpreting performance data. Sources of masking include plant configuration (AC/DC ratio); instrumentation (soiled pyranometer); and exclusions in availability reporting. A new duration curve is presented and used to qualitify masking by nverter clipping and soiled pyranometers. "Masked" Performance Ratio is typically 2% to 5% higher than the actual Performance Ratio, but may be higher.