Numerical Simulation of the Bypass Diode Failure Resistance and those Power Consumption in a Photovoltaic Solar Module with Failed Bypass Diode

The use of photovoltaic systems (PVSs) has significantly increased. However, the number of cases in which accidents or failures in PVS result in burnout has also witnessed a surge. In particular, there have been cases in which the bypass diode (BPD) in a photovoltaic (PV) module fails because of lightning damage. bypass diode failure is associated with the risk of burning. Previously, we reproduced failure cases in which a single bypass diode fails at various resistance values in a three-cluster PV solar module to identify bypass diode failures and their burnout risks. However, when using simulated power supplies that reproduce the output of PV solar modules and PV solar modules, the verification of the risk of burnout owing to bypass diode failure at the string or array level requires a large-scale PVS. In addition, a PVS has a variety of system output characteristics. However, it is desirable to easily verify the risk of burnout owing to the bypass diode failure of PV solar modules under various PVS output conditions. Hence, in this study, numerical simulations were performed using MATLAB/Simulink to simulate the power consumption of a failed bypass diode in a solar module when the bypass diode fails at various bypass diode failure resistance values (RF). In addition, an experiment reproducing the same conditions as were used in the numerical simulation was conducted to investigate both the risk of burnout in the case of the failure of the bypass diode of the solar module and confirm the validity of the numerical simulation. In the numerical simulation, when RF was approximately 4 Ω, the power consumption of RF was maximized at 14.0 W. Therefore, during the maximum power point tracking operation of a three-cell string PV module with one failed bypass diode, the amount of heat generated was high when RF was approximately 4 Ω. In an experiment that used a power supply to simulate PV characteristics, the RF power consumption was also maximized at 14.6 W when RF was approximately 4 Ω. Therefore, the proposed numerical simulation model successfully reproduces the output characteristics of a PV module with a failed bypass diode. Hence, analyzing bypass diode failures in large-scale PV systems is possible, even though it is difficult to perform such experiments.