The penetration of photovoltaic (PV) systems in power grids has substantially increased since the recognition of renewable energies. In a high solar-integrated network environment, an accurate forecast of the expected solar energy output is vital. One of the important factors that influence such forecast is the failure rates of PV systems. Therefore, a new and realistic reliability model of the PV system is proposed in this study. In contrast to the conventional reliability model, which uses

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... ed values of failure rates in a year, the proposed model considers various weather conditions, detailed PV system architecture, manufacturing quality and other necessary materials to determine the time-varying failure rates of the PV system. Results reveal that the proposed model produces monthly failure rates that are considerably different from the fixed yearly failure rate in which the difference in high latitude regions is more significant than that in tropical climate regions. INDEX TERMS Failure rate, PV system, reliability, time-varying. VOLUME 8, 2020 This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see http://creativecommons.org/licenses/by/4.0/