Research on Early Aging Fault Identification of Photovoltaic DC Combiner System

In order to detect typical faults in the photovoltaic Direct current (DC) system, this paper first compared and analyzed the frequency domain responses of two typical faults in the photovoltaic DC system at different insulation aging stages based on the early insulation aging theory and the insulation aging characteristics of DC transmission cables. A fault identification method based on the harmonic trajectory of the primary and secondary switch frequencies for pole-to-pole short-circuit faults was proposed. The feasibility of this fault identification method was verified through the controller algorithm and combined with the hardware experimental platform. This method utilizes basic mathematical theorems, and the code configuration is easy to implement. At the same time, adjusting the sliding-window coefficient and the threshold coefficient can change the sensitivity and false-alarm rate of the algorithm, achieving different levels of fault-identification accuracy and leading to the best results. A 90% accuracy and a false-alarm rate lower than 10% can be achieved, opening up new ideas and methods for photovoltaic fault identification. Experimental results show that this method has a fast fault identification speed, with an identification time ranging from 10 to 20 ms, and can achieve different levels of identification accuracy by flexibly adjusting the control parameters.