Study On Reactive Power And Voltage Optimization Of Grid Connected Wind Farm Considering The Decentralized And Coordinated Control Of Dfig

With the development of industrialization and the need of environmental protection,the dependence of human on clean and renewable energy is gradually deepened.The proportion of wind power generation in the power grid is gradually increasing.However,the regions with abundant wind energy resource in China are generally at the end of the power grid.The wind power is intermittent and volatile,and the power output is not stable,which also has an impact on the voltage quality of the system.The optimization of the voltage and reactive power in the wind farm is carried out with the voltage and reactive power regulating equipment under the decentralized coordination control of the doubly fed induction generator(DFIG).At the same time,with the extensive development the effect of wind power storage system on voltage and reactive power can’t be ignored.The main contents of this paper are as follows:At first,the characteristic of the reactive power and voltage of the wind farm are analyzed.The relationship between the voltage and power of the wind farm is studied by establishing a simplified model of connection between the wind farm and the grid.According to the "double reaction theory",the decoupling control of the active and reactive power of DFIG is carried out,then the reactive power limit is calculated.The reactive power flow distribution in the wind farm is expounded which is caused by the transformer and the line.The principle of reactive power compensation in wind farms is studied.Six kinds of regulation equipment of voltage and reactive power are introduced,and the selection of reactive power compensation capacity is carried out.Moreover,the method of power flow calculation in the wind farm is researched.The objective functions,which separately consider the security and the economy,are analyzed.The optimization model is established to minimize wind power loss and voltage deviation,with each DFIG reactive power,dynamic reactive power compensation device and transformer tap as the variable,which combined with the constraints in the wind farm operation process.The principle and solving steps of the linear decrement weight particle swarm optimization(LinWPSO)algorithm are studied,and a method for dealing with discrete optimization variables is proposed.The steps of decentralized coordinated control of voltage and reactive power optimization in wind farm are analyzed.The effectiveness of static and dynamic optimization is verified by example simulation.At last,the centralized and decentralized energy storage system is analyzed in the light of the situation of installing the energy storage system in the wind farm.The hybrid energy storage system including the super capacitor and the battery group is determined,and the power distribution is carried out.On the basis of considering the power constraints of energy storage system,a reactive power optimization model with energy storage wind farms is established.Wind farms with centralized and decentralized energy storage systems are respectively built.The simulation results verify the effect of energy storage system on voltage and reactive power optimization.