Research Of Voltage Stability Problem In The Power Grid With New Energy Plants

As the effective method to solve the problem of energy and the environment,new energy power generation technology has been widely used now.Wind power and photovoltaic power generation technology are the most mature ones,so that national policy has a bias to wind power and photovoltaic power generation.Under the lead of the policy,two types of power generation capacity grow rapidly in recent years.New energy,however,may bring a lot of problems to the grid operation when operate with the grid,mainly in pow er quality deterioration,power supply reliability,voltage stability,the scheduling difficulties,etc.So,studying how to reduce the negative impact of the new energy grid generated will further promote the development of new energy power generation tec hnology.In view that the wind power has caused substantial impact to operation of power grids,because of its output volatility,this paper mainly consider the randomness of the wind power,combine with the reactive power regulation characteristic,discus s its reactive power optimization theory of distribution network.Firstly,this paper introduces and analysis development trends of voltage control technology,the reactive power optimization model and related algorithm at home and abroad.Then discuss the influence of new energy power active power and reactive power output to the grid from the perspective of power flow.In addition,analyze the reactive power regulation characteristic of wind turbines,photovoltaic battery and reactive power compensation devices.Then put forward a two-layer optimization model which considered two time scales based on existing AVC mode.To solve the proposed model,this paper propose a combined algorithm including branch and bound method and the constrained function method.In order to verify the correctness of the above theory,this paper build an eleven-node network model and three of them are the wind farms.In the case of grid connected and off-grid,contrast and analysis the influence of wind power to the network operation,and then set up different scenarios,verify the effectiveness of the two layers of optimization respectively.Finally,in order to analyze the adaptability of proposed method,the worst case of optimization results were obtained.Results show that the proposed method can not only reduce the influence that new energy caused on reactive power distribution and voltage of power grids,but also can reduce the number of switching and capacity of the capacitor.