Research On DC Series Arc Fault Detection And Protection Strategy Of Photovoltaic Grid-Connected System

In recent years,China has accelerated the promotion of clean,low-carbon,safe and efficient utilization of energy,making photovoltaic power generation widely used in many fields.The DC side of the photovoltaic system is easily affected by environmental factors,which will produce continuous burning arc,thus causing fire accidents and endangering the safe operation of the photovoltaic system.In this paper,a fast and accurate series arc fault detection method is proposed for the DC side series arc fault of photovoltaic system,and the protection strategy is formulated.In this paper,the characteristics of photovoltaic grid-connected system and DC arc are analyzed.On the theoretical basis of the characteristics of photovoltaic grid-connected system,the main factors affecting the output characteristics of photovoltaic system are analyzed,and the working principle of photovoltaic grid-connected system is studied.Based on the theory of DC arc characteristics,the factors affecting the stable combustion of the arc are analyzed,and the change law of line current when the arc fault occurs is studied,and the characteristic values of the fault arc are extracted.Aiming at the problem of poor accuracy of arc fault detection in time domain,threshold filtering was firstly adopted to remove noise interference in photovoltaic system to highlight the fault characteristics of arc.Then the acquisition of normal and fault arc signal changes from the current effective value,standard deviation and sample entropy analysis,put forward suitable for photovoltaic system series dc arc fault detection method,through the experiment to determine the detection criterion value,at the same time the inverter startup and interconnection,different weather factors,and analyses the effect of different arc clearance,etc,to verify the accuracy and anti-interference performance of the test method.According to the detection method of DC series arc fault in photovoltaic grid-connected system,the protection strategy of DC series arc fault is put forward.The protection strategy does not need to add additional electronic equipment,but only needs to improve the main circuit of the inverter,adding the current acquisition,arc detection,trigger control,locking control,reswitch control and other parts of each series branch,so as to realize the separate operation,real-time detection and protection functions of each series branch.The feasibility of the proposed fault detection and protection strategy for DC series arc in photovoltaic grid-connected system is verified by experiments.