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Optimisation of DC/AC Ratio in Different Climatic Zones: A Technical Analysis on a Sub-Hourly Level
I. Meyer, A. Salles, J. Tellez Mejia, V. Vorasitchai, S. Chitiva Bocanegra, N. Cherdsanguan
LCOE, DC/AC Ratio, Sub-Hourly Modelling, GHI Fluctuations, Inverter Clipping
PV Systems and Storage – Modelling, Design, Operation and Performance
Subtopic: Design and Installation of PV Systems
Event: 37th European Photovoltaic Solar Energy Conference and Exhibition
Session: 5CV.4.6
1610 - 1615
ISBN: 3-936338-73-6
Paper DOI: 10.4229/EUPVSEC20202020-5CV.4.6
0,00 EUR
Document(s): paper, poster


The DC/AC ratio is a key design parameter of solar PV plants. In recent years, the cost reduction in PV modules has led to increased DC/AC ratios. Our experience shows that such designs are often mis-optimised because the impacts of sub-hourly irradiation fluctuations and PV module degradation are not adequately accounted for using standard industry software. Seven sites located in tropical and temperate climate have been analysed, along with an eighth control project located in a desertic climate where minimal cloud cover is present. To estimate the DC side inverter clipping losses of each system, hourly and sub-hourly (10min and 5min) yield modelling of a standardized 1MWAC system was performed in PVsyst, varying the DC/AC ratio from 1.2 to 1.7. The clipping loss was calculated over the 25-year life of the plant taking the module degradation into consideration, and the LCOE for each site and system configuration was found based on simplified CAPEX and OPEX assumptions. The analysis performed shows that yield modelling on an hourly basis, underestimates the DC side inverter clipping of systems in tropical and temperate climates where moderate to high variation in cloud cover occurs. Systems optimised on sub-hourly basis may therefore result in lower installed DC capacity, in the range of 2-6%, thus an overall lower CAPEX, and higher financial returns for developers.