Detection and Classification of Faults in Solar PV Array Using Thevenin Equivalent Resistance

Detecting fault in a solar photovoltaic (PV) array in the presence of protection diodes (bypass and reverse blocking) is complex. This is because variations in the electrical parameters (due to a fault) are often not distinguishable from one type of fault to another or from fault to partial shading. Depending on the fault condition, an open fault may appear like a short-circuit fault and a severe partial shading occasionally may be detected as a short-circuit fault. Identifying a short-circuit fault and separating it from an open fault or partial shading are important as the former demands immediate attention to avoid damage to the PV modules and fire hazard. It is observed that the available techniques, based on transient changes in array parameters and model comparison, cannot identify faults under all practical scenarios. In this article, a fault detection and classification technique using array voltage, current, irradiance, and temperature measurements is proposed. The technique computes Thevenin equivalent resistance of the PV array for accurate fault identification. The simulation results demonstrate that the proposed technique can detect and classify faults correctly and differentiate them from partial shading. The comparative results show its superior performance compared with available techniques. The proposed technique is also validated by the results of hardware experiments.