Fault Diagnosis and Control Strategies in Photovoltaic Systems: Recent Advances in Reliability Improvement, Lifetime Extension, and Waste Reduction

The continuous growth of photovoltaic (PV) installations worldwide has increased the need for reliable and sustainable energy conversion systems. Failures occurring in PV modules, power electronic converters, and control units can significantly reduce energy production, accelerate component degradation, and shorten system lifetime. This structured narrative review synthesizes the literature published primarily between 2015 and 2026, with particular emphasis on studies from 2020 to 2026; earlier publications are included selectively when they provide foundational or normative concepts relevant to contemporary PV systems. The review examines recent developments in fault detection, diagnosis, and control techniques, including electrical and model-based methods, thermal and luminescence imaging, artificial intelligence, maximum power point tracking, and fault-tolerant control. Particular attention is given to the integration of diagnostics with predictive maintenance, remaining useful life estimation, digital twins, and operational decision-making. Rather than considering these areas independently, the review links fault occurrence, detection, diagnosis, prognostics, control or maintenance action, reliability improvement, service-life extension, and waste reduction within a common lifecycle-oriented framework. The available evidence indicates that early fault detection, targeted maintenance, and appropriate control can limit secondary damage, reduce unnecessary component replacement, and improve resource utilization, although direct quantitative evidence linking diagnostic actions to additional service years or avoided waste remains comparatively limited. The review also identifies current challenges related to cross-site generalization, multimodal data fusion, edge deployment, second-life qualification, and the integration of reliability and circular-economy indicators.