| In the past,climate change caused by the large consumption of fossil fuels was considered to be one of the major threats to life on earth.It affected the oceans,atmosphere and land widely.Nowadays,clean and environmentally friendly renewable energy has become one of the main sources of energy supply.For Liaoning Province of China,the installed capacity of distributed photovoltaic power has reached millions of kilowatts,and supported by national policies,the installed capacity and energy share of distributed photovoltaic power will be further increased.The random fluctuation of solar irradiance is one of the main disadvantages of large-scale application of photovoltaic in distribution network.Due to the increasing penetration of photovoltaic in distribution network,the power quality of distribution network is seriously affected.Therefore,this paper will make a detailed study on the different ways of connecting distributed photovoltaic power generation into the distribution network and the impact on the distribution network,aiming to solve the adverse impact of photovoltaic on the distribution network.The specific research contents are as follows:Firstly,this paper studies the grid connection mode and current situation of distributed photovoltaic power generation,analyzes the specific characteristics of distributed photovoltaic power generation,and studies the characteristics,rules and requirements of grid connection of photovoltaic power in the distribution network considering different grid connection modes(special line grid connection and T-connection grid connection).The equivalent circuit model of photovoltaic power generation is studied,and its power generation principle is modeled,and then the impact of grid connected on power quality(voltage distribution,voltage fluctuation and voltage harmonics),distribution network structure,electrical equipment and economic operation is analyzed.Secondly,the equivalent circuit model of distributed photovoltaic power generation after grid connection is studied,and the mathematical model and calculation steps of common calculation methods of distribution network are given,and the power flow calculation method of distribution network after grid connection of distributed photovoltaic power is proposed.Through simple 13 node distribution network model,the influence of distributed photovoltaic on voltage distribution of low-voltage distribution network is studied After the grid connected,the voltage of each node along the feeder will rise.Finally,this paper studies the 10 k V distribution network in a local area of Shenyang City,Liaoning Province,considering the situation that a single node is connected to photovoltaic with different capacity,when the photovoltaic output is constant,when the photovoltaic output is constant,and when multiple nodes in the distribution network are connected to photovoltaic at the same time.In addition,the influence of load fluctuation on distribution network and the influence of photovoltaic output fluctuation on distribution network voltage distribution are also considered.At the same time,in order to suppress the impact of photovoltaic grid connected on the voltage fluctuation of distribution network,the solution of reducing voltage fluctuation by photovoltaic inverter is proposed. |
