Research And Application For The Voltage Quality Evaluation And Regulation Method Of The Low-Voltage Distribution Networks

Nowadays,distribution networks of 380 V low voltage level widely adopted in the way of one directional radiant power supply with the tree structure and multi-branches form in our country.These distribution lines feature in low power factor,large power loss and poor end voltage quality.On one hand,because of the high power loss rate of 380 V low voltage distribution networks,it brings a lot of unnecessary economic losses to electric power enterprise.On the other hand,380 V low voltage distribution networks will make a lot of sensitive household electrical appliances,such as air conditioner,television,computer,functioning unnormally and even damaged.In order to improve the voltage quality of low-voltage distribution networks in Shanghai,this paper firstly analyzes the causes of low voltage grid voltage problem,and then introduces some basic voltage regulation measures.At present,the main causes of the voltage problems in the low-voltage distribution area are small wire cross-section area,unreasonable distribution capacity,excessive load rate,unreasonable load power factor,low transformer tap position and three-phase load imbalance etc.The mainly regulation measures are distribution transformer on-load voltage regulation,reactive power compensation and three-phase load adjustment that are commonly used nowadays.Then introduces the principle,method and application conditions of each.This paper introduces the above points.Secondly,this paper designed a voltage quality evaluation and regulation decision system.By means of obtaining the basic parameters of low-voltage areas and calculate the status quo by three-phase current calculation of the weak ring distribution networks based on the modified back/forward sweep method and load sharing algorithm.Then it adopts the low-voltage distribution areas and lines low voltage analysis algorithm to give a reasonable evaluation analysis and regulate schemes.It can effectively support the managers of electric power enterprises to carry out low voltage regulation measures.At the same time,low voltage quality evaluation and regulation model of low-voltage distribution network is established.Finally,some real low-voltage area networks from Shanghai Pudong and Jinshan power company are selected for analysis and evaluation.Then reasonable regulation plans for the existing problems have been put forward.In addition,this paper also selected three low-voltage areas networks for evaluation and analysis,along with onsite regulation verification.Both of these cases achieve a desired effect.By establishing the voltage quality evaluation and regulation decision system,his paper applies it to the low-voltage area networks of Shanghai Pudong and Jinshan,and proposes special evaluation and regulation schemes.It solved the low-voltage quality problems practically,and fundamentally changed the situation that only rely on experience and regulate blindly.Optimal effect has been realized with the minimality of the voltage regulation investment.