Research On Three-phase Unbalance Governance Of Distribution Transformers Based On Phase Change Switch And SVG

When the distribution transformer is in three-phase load imbalance,the load side will generate zero sequence current and harmonic current,due to the disturbance of both,the distribution transformer will generate a lot of heat,increase copper loss and reduce power output capacity,which seriously affects the power quality.At present,the most commonly used three-phase imbalance management method is to install phase change switch on the load side or SVG(Static Var Generator)on the power side.In addition to ensuring that the power quality is up to standard,the installation method of the management device must be considered to achieve the best management effect and economic effect.In this paper,we use phase change switch and SVG to manage the three-phase imbalance of distribution transformer.For the three-phase imbalance on the load side of distribution transformers,this paper adopts the management method of installing phase change switches at specific nodes.To face the three-phase load imbalance distribution problem,this paper establishes a model with the minimum three-phase current imbalance and the minimum number of operating switches as the objective function,and solves the optimal load distribution model by using an improved particle swarm algorithm.Finally,it is verified through Matlab simulation that the load distribution scheme solved by the improved particle swarm algorithm can effectively reduce the three-phase unbalance degree on the load side,reduce the number of phase change operations,and distribute the load in a balanced manner;in order to improve the effect of three-phase unbalance management,this paper takes the lowest line loss and the lowest distribution transformer loss as the objective function to establish the model,and uses the improved genetic algorithm to find the optimal installation position of phase change switches on the load In order to improve the effect of three-phase imbalance management,this paper establishes a model with the lowest line loss and the lowest distribution transformer loss as the objective function,and uses an improved genetic algorithm to find the best installation position of the phase change switch on the load side.For the three-phase imbalance on the power side of distribution transformer,this paper adopts the installation of SVG on the power side of distribution transformer for reactive current compensation management.The combination of instantaneous reactive power theory and current detection method is used to separate and detect the unbalanced load current.It provides a theoretical basis for the three-phase unbalance governance on the power side of distribution transformers.Finally,combining the advantages of phase change switching and SVG governance,we study the scheme of the two together.The feasibility and effectiveness of this scheme is verified by comparing the simulation results of phase change switch + SVG and phase change switch independent governance scheme through Matlab/simulink simulation.This study enriches and expands the theoretical framework and analysis methods for the study of three-phase imbalance governance of distribution transformers.Compared with the traditional method,the use of phase change switch and SVG with governance can effectively solve the current and voltage imbalance caused by load imbalance,greatly reduce transformer losses,improve output power quality,reduce the investment cost of governance,delay the aging of lines,extend the service life of distribution transformers,and reduce power maintenance work.At the same time,the method can guarantee the safety and stability of users’ electricity consumption,and provide the scientific decision-making method and theoretical basis for three-phase unbalance management in the urban and rural power grid transformation projects of the power grid enterprises,and contribute to the cause of energy saving and emission reduction of the society,which has good promotion and application value.