Coordinated Strategy For Reactive Power And Voltage Control In Wind Farm

Wind power generation is developing rapidly in China.The access of wind farm may have a bad effect on the stability of power system.Among the problems brought by connected wind farm,the reactive power-voltage problem of wind farm is especially concerned.Most studies focus on the interaction between wind farm and power system.Compared with the existing power system,the capacity of wind farm is small.In many studies,wind farm are usually equivalent to a load or a wind turbine with the same capacity and the reactive power-voltage problem of wind farm is ignored.However,with the rapid expansion of scale,the increasing capacity of grid connection and the diversification of the layout and operation mode of wind farm,reactive power and voltage problem in wind farm are increasingly prominent.Therefore,it is of great significance to study the coordinated strategy of reactive power and voltage control in wind farm.The main work of this paper is as follows:First,the reactive power and voltage characteristics of main equipments in wind farm are studied.The reactive power and voltage regulating equipment in wind farm includes various wind turbines and reactive power compensation equipments.The reactive power loss in wind farm mainly includes the reactive power loss of the transformers and the transmission lines.The calculation method of reactive power generation limits of doubly fed induction generator set is given.Secondly,the natural distribution of voltage and the effect of the reactive power compensation equipment on voltage distribution in wind farm are studied.The natural distributions of voltage under different conditions,such as different active power output of wind turbine,different power fators of wind turbine,different line types of power collection system,are analyzed.The influence of the reactive power compensation equipment on voltage level of each node in wind farm is analyzed.Finally,a coordinated strategy of reactive power and voltage control in wind farm is proposed.First,according to the prediction results of the wind farm active power output,the total reactive power demand of the wind farm can be estimated.Then according to the principle of reactive power allocation,the output of each reactive power equipment is allocated.This is first voltage adjustment.In actual operation,if there is any node's voltage in wind farm exceeds the specified range,the equpment with reactive power margin in wind farm will be used to carry out the second voltage adjustment.An example is applied to verify the strategy,and the result shows the effectiveness of this strategy.