Incipient Fault Identification-Based Protection for a Photovoltaic DC Integration System

In a photovoltaic (PV) DC integration system, a DC line-to-line short-circuit fault will cause all converters to be quickly locked. This can result in the sustained outage of the system. In this study, to address this problem, a protection method based on incipient fault identification is proposed to quickly identify and isolate the faulty branch, and to prevent the incipient fault from developing into a short-circuit fault. By analyzing the frequency characteristics of the incipient fault current, a disturbance injection start criterion is formed. Then, by using the converter to inject small disturbance signals to form obvious fault characteristics, the location and isolation of the faulty area can be achieved in time. The loop simulation results based on real-time digital simulator (RTDS) hardware demonstrate that the proposed method accurately recognizes the incipient fault without affecting the system power quality, and can simultaneously isolate the incipient fault. These factors provide guarantees for the safe and efficient operation of PV DC integration systems.