Research Of Three-phase Unbalanced Control Of Distribution Network

Weinan City distribution network after recent years of transformation,the annual fault repair volume is significantly reduced.However,with the rapid expansion of urban areas and towns,a large number of new three-phase users have unreasonable layout of internal lines,and there are large differences in power consumption habits and time,resulting in the imbalance of three-phase current in some distribution transformers,and even overload and three-phase imbalance in distribution transformers.In this case,the output of the distribution transformer is reduced,the neutral current is large,and the three-phase voltage is correspondingly increased or decreased,resulting in unqualified voltage,potential electric shock of the grounding down lead,burning of the user’s electrical equipment,burning of the distribution transformer and other consequences.Therefore,it is of great practical significance to solve the three-phase load imbalance problem of 0.4kV distribution network in Weinan City.The three-phase unbalance status of zhangdongnan substation in Weinan City is studied.The single-phase load accounts for 81%of the total power load.The randomness of power consumption and the unsatisfactory electrical location distribution of single-phase load are the main reasons for the unbalanced three-phase current in zhangdongnan substation.The more serious the three-phase imbalance is,the more serious the additional power loss of the line and transformer,and the current flowing through the middle line point will also increase,which will cause additional voltage loss and severe heating of transformer and electrical equipment Important issues.Therefore,it is very urgent and necessary to control the three-phase imbalance of zhangdongnan substation in Weinan City.The SVG three-phase unbalance control scheme based on load compensation is presented.The scheme can comprehensively solve the three-phase imbalance,low power factor,harmonic and other problems.It is suitable for the lines with higher requirements for power governance,and can better solve the three-phase imbalance of zhangdongnan substation.The working characteristics,advantages and disadvantages of SVG and SVC in the load compensation method are studied.Compared with SVC,SVG has stronger reactive power compensation ability,faster response speed,filtering function,simple operation and easy maintenance.Simulation results show that the SVG system compensation can effectively control the three-phase imbalance of 0.4kV distribution network in zhangdongnan substation.This paper studies and analyzes the implementation effect of the three-phase imbalance control scheme of zhangdongnan substation.Through the research on the current data of the transformer,the unbalanced current to be compensated is obtained,and the installation method of SVG is determined.The statistical analysis of the data before and after the treatment of the three-phase imbalance problem of zhangdongnan substation distribution network in Weinan City shows that the average three-phase imbalance degree in the whole day is less than 15%,the three-phase unbalance problem of zhangdongnan substation in Weinan has been fundamentally solved.