Research On Key Technology Of Comprehensive Efficiency In Medium And Low Voltage Distribution Network

The construction and operation management of medium-low voltage distribution network is the weak link in the construction of power grid in China.Its loss reduction and efficiency is a focus of energy conservation and emission reduction work but also a difficult point for power loss reduction.The power loss of the medium-low voltage distribution network occupies a large proportion in the whole power system.Due to the relatively weaker structure,there is a gap in the domestic distribution network loss and equipment utilization level with the developed countries.The comprehensive benefits of the distribution network need to be further improved.Over the past decade,the distribution network construction investment has reached one trillion yuan,distribution network investment construction and operation management is lagging behind,the medium-low voltage distribution network comprehensive efficiency work is facing enormous challenges.Based on the current situation of the energy saving and loss reduction measures for distribution network and concluded on the previous studies,this paper summarizes the key technologies of medium-low voltage network in the comprehensive efficiency,distribution transformer selection,low voltage reactive power compensation and equipment utilization evaluation,mainly for the following work:Firstly,the mechanism of the loss of the medium-low voltage distribution network is analyzed briefly,and the power flow calculation model is established.Secondly,the method of decreasing loss and increasing the efficiency in distribution network is studied from two major aspects.On the one hand,choosing the type and capacity of distribution transformer scientifically and rationally.On the other hand,the dynamic reactive power optimization method for distribution network considering the maximum allowable number of times of the capacitor bank is studied.In the aspect of distribution transformer selection:Based on load data acquisition level,an optimization method of distribution transformer considering data acquisition difference is proposed and different loss cost models are built respectively.This paper establishs an optimization principle of the lowest distribution transformer life cycle cost(LCC),taking into account initial cost and later operation maintenance cost.The change trend of LCC with capacity under different distribution types is analyzed.Dynamic reactive power optimization of medium-low voltage distribution network:The mathematical model of reactive power optimization considering the adjustable number of equipment is established,and the minimum power loss as the objective function,so that the reactive power compensation device can avoid the frequent operation while following the load reactive power compensation device too frequent action with the load fluctuation.The corresponding calculation program is compiled in MATLAB platform by genetic algorithm,the strategy of daily switching of reactive power compensation device is proposed,the group has made full use of the capacitor.The reactive power compensation scheme are analyzed from the aspects of investment cost and profit loss In this paper,the time value of capital is considered in the cost and benefit.Finally,from the aspects of management efficiency,a comprehensive efficiency evaluation model based on equipment utilization is proposed.Through the analysis of the factors affecting the utilization of equipment,the evaluation index of distribution transformer and reactive power compensation equipment utilization is established,and then put forward measures to improve equipment utilization,which is of great theoretical reference and practical application significance to improve the construction and management level of the distribution network in China.