Numerical Simulation of Output Characteristics of Photovoltaic Module with Short- and Open-Circuited Bypass Diodes

In recent years, decarbonization efforts have advanced rapidly, especially in developed countries, due to climate change and rising energy costs. Photovoltaic (PV) power generation is being widely adopted as an effective energy source, but increasing penetration brings operational problems such as failures. For example, bypass diode (BPD) failures in PV modules can cause heating, burning, fire, and electric shock risks. BPDs protect against electrical continuity problems and hot spots under partial shading, but failures are difficult to detect when modules are roofmounted. Failed BPDs exhibit different electrical characteristics, ranging from short- to open-circuit failures, with varying heat generation. The authors previously clarified the correlation between resistance and heat generation using a single PV module, but verification for systems with multiple modules requires large-scale testing, making simulations desirable. We propose a model that simulates the output of a PV module string with a failed BPD at various fault resistances. The model reproduces the output when one BPD fails in a PV module with three cell strings and is validated against measured data from a failed BPD module. The study successfully reproduced outputs of PV modules with shortcircuit failures (0.1–50 Ω) and open-circuit failures, and also situations with partial shading. The model is expected to support understanding failure mechanisms and diagnosing PV system faults.