Phase Sequence Optimization And Energy Efficiency Evaluation Of Low Voltage Distribution Network Under Unbalanced Three Phase Load

For the low-voltage distribution network,long term of three-phase unbalanced state will lead to the increase of the loss of the distribution line,the reduction of the output power of the transformer,the increase of the loss of the transformer and so on,which will reduce the comprehensive energy efficiency of the low-voltage distribution network.Therefore,it is of great significance to put forward effective measures to reduce the line loss caused by three-phase load imbalance in low-voltage distribution network,and to establish appropriate indicators to analyze the energy efficiency of low-voltage distribution network under three-phase imbalance,so as to achieve the carbon neutral goal of the low-voltage distribution network.In this paper,the phase sequence optimization and comprehensive energy efficiency of low-voltage distribution network are analyzed and studied.The main work is as follows:Firstly,based on the line loss calculation of three-phase unbalanced low-voltage distribution network,this paper proposes to use the outlet current curve substitution method to establish the user load model,and then calculate the split phase power flow to obtain the theoretical line loss calculation method of low-voltage distribution network.Then,from the perspective of artificial commutation,an artificial phase sequence optimization method based on load forecasting and non-dominated sorting genetic algorithm(NSGA2 algorithm)is proposed,which mainly forecasts the operation parameters on the day of phase modulation,and then establishes the phase sequence optimization model of low-voltage distribution network by comprehensively considering taking the minimum line loss and the minimum number of phase modulation as the objective function based on the prediction operation parameters.The model is solved by using the method of NSGA2 algorithm.The effectiveness of the proposed method is verified by comparing the line loss and three-phase load imbalance of a low-voltage distribution network in Anhui power grid under the original state,this optimization scheme and other platform optimization schemes.Finally,from the perspective of energy efficiency evaluation,according to the selection of energy efficiency evaluation index of low-voltage distribution network in Technical guide for energy efficiency evaluation of medium and low voltage power distribution networks(GB / T 31367-2015),considering the impact of three-phase load imbalance on low-voltage distribution network,a comprehensive energy efficiency evaluation system of low-voltage distribution network under three-phase load imbalance is proposed,The comprehensive weight method of AHP-EWM is used to calculate the weight of each index,and the energy efficiency level of low-voltage distribution network under unbalanced three-phase load is quantified.Through the energy efficiency evaluation of the scheme before and after the phase sequence optimization,it is proved that the energy efficiency evaluation system constructed in this paper is feasible and scientific in evaluating the energy efficiency level of low-voltage distribution network under three-phase imbalance.