A String-Current Behavior and Current Sensing-Based Technique for Line-Line Fault Detection in Photovoltaic Systems

The normal operation of a photovoltaic (PV) system is undermined by line-line (LL) faults. An LL fault, which establishes an unintentional current path between two points of different potentials, can cause malfunctions and even fire hazards to the PV systems. Although the overcurrent protection devices such as fuses are utilized to terminate the LL faults, the maximum power point tracking (MPPT) controller, partial shading, and blocking diodes are affecting the fault currents and they may be lower than the rated current of the fuse. Therefore, it is necessary to develop an effective LL fault detection technique for the PV systems. In this article, an LL fault detection technique based on the string-current behavior and current sensing is proposed. The characteristics of the LL faults and the string-current behavior under various fault conditions were analyzed to develop the algorithm. The proposed technique could determine the occurrence, type, location, and percentage of the LL faults. It was verified that the fault detection algorithm and current sensors in specific locations could effectively detect the LL faults despite the effects of MPPT, partial shading, and blocking diodes.