An Efficient String Current Correlation-Based PV Array Fault Detection Technique

Standard protection devices, such as overcurrent protection devices (OCPD) or ground fault protection devices (GFPD), fail to detect faults due to the presence of series blocking diodes in a series–parallel configured solar photovoltaic (PV) array. This is because, the blocking diode limits the fault current below the respective threshold of the OCPD or GFPD fuses. Several techniques are available in the literature, which attempt to overcome the ineffectiveness of the protection devices in the presence of series blocking diodes. However, the common limitation of these techniques are that they fail to distinguish a fault from partial shading conditions. This can lead to false positives affecting productivity. To overcome the shortcomings of the available techniques, this work proposes a string current correlation-based fault detection technique for PV arrays, which is also effective under partial shading conditions. This work also computes a threshold value of the anticorrelation between the string currents that separates faults from partial shading. MATLAB simulations considering various fault types and weather conditions show its effectiveness in detecting faults and separating it from partial shading. A small-scale hardware set-up is also developed to establish the applicability of the proposed technique in a real-world scenario.