Passive oscillator based protection scheme for faults within utility-scale photovoltaic arrays

Undetected faults within photovoltaic (PV) arrays can result in permanent power loss and major catastrophic failures. This paper proposes a passive oscillator based protection scheme that detects and classifies string-to-ground, string-to-string, and open-circuit faults in utility-scale PV arrays. A passive oscillator that consists of an inductor and a capacitor is placed on each string. A real-time discrete wavelet transform (DWT) is used to detect the voltage transients generated by the oscillator in less than 3 ms. Some salient features of this method include its capability to distinguish between fault and partial shading conditions, and its independence from meteorological data. The performance of the proposed approach is assessed on a utility-scale grounded PV arrays under various conditions. The results verify the scheme's sensitivity, selectivity, and high speed.