Research On The Comprehensive Control Technology Of Unbalanced Three-phase Load In Low-voltage Area

Three-phase load imbalance in low-voltage station is one of the common and difficult problems in power supply enterprises.At present,most of the low-voltage three-phase four-wire power supply lines in China are prone to three-phase load imbalance due to unbalanced single-phase load distribution and asynchronous use.Serious three-phase load imbalance not only affects the safe and reliable operation of transformers,motors and lines in the distribution network,but also increases the loss of lines and reduces the power quality.It is of great significance for improving power quality,safety and economy of distribution network to study the three-phase load imbalance control scheme in low-voltage station area.Firstly,the background and significance of the research on three-phase load imbalance are described.Through the research at home and abroad,it is found that in addition to the manual commutation,the current three-phase load imbalance treatment methods mainly include distribution network reconstruction method and reactive power compensation method.Through research and analysis,these two methods have some problems,such as imperfect functions,large floor space,high cost and certain influence on power grid,which limit their wide use.Secondly,the measurement automation system is used to monitor the load in the common station area of Huizhou Power Supply Bureau and collect the three-phase unbalance data,extract the sample of typical stations and load characteristic data,and study and analyze the current situation and causes of the three-phase unbalance station area of Huizhou Power Supply Bureau.At the same time,a theoretical calculation model of low-voltage distribution network was established based on distribution transformer operation parameters,user load quantity data and low-voltage network structure parameters,so as to quantitatively analyze and evaluate the harm and influence of three-phase load imbalance on the safety,reliability and economic operation of low-voltage distribution network.On the basis of summarizing and analyzing the cause of three-phase load imbalance,the harm and the limitation of the current treatment technology,the paper focuses on the application of two new technologies.Firs,to compare all kinds of reactive power compensation device to control the three-phase unbalanced load effect,the building load reactive power compensation and give attention to two or morethings balanced three-phase load coordinated control algorithm,the optimization design to adjust theunbalance current of converter type reactive power compensation device,and through software simulation modeling and analysis to evaluate the unit management to improve the effect of three-phase unbalanced load.Second,based on the analysis of user load characteristics,research and develop intelligent load balance calculation and control strategy to maximize the realization of intelligent commutator with reasonable equalization of three-phase load according to load changes,and analyze and evaluate the improvement effect of the device on the treatment of three-phase load imbalance through software simulation modeling.At last,two typical low-voltage stations are selected as the pilot,and the three phase load imbalance is treated by using the converter type reactive power compensation device and the intelligent commutation device respectively.Combining with the practice and application of typical platform area,the economic evaluation is carried out on it,and the comprehensive control measures are put forward from the aspects of technology and management.