Research On Reactive Voltage Control Strategy Of Wind Farm Under High Proportion Of Wind Power Integration

With the further deepening of the energy supply side structural reform,high proportion of wind power grid operation is the inevitable trend of the future development of the power system.Wind power output is highly volatile and the capacity of wind turbine to withstand voltage is insufficient.The replacement of traditional power supply with a high proportion of wind power will reduce the dynamic reactive power support capacity of the system,which seriously threatens the safe and stable operation of the power system.Therefore,the voltage stability of power system with wind power has become a key factor affecting high proportion of wind power integration,and the reactive voltage control strategy of wind farms under high proportion of wind power integration needs to be further studied.The specific research work of this paper is as follows:(1)Evaluation method of maximum wind penetration considering static voltage stability constraint.Firstly,the permanent magnet direct drive wind turbine is taken as an example to analyze its mathematical model and operation characteristics.Then,combining with PV curve method,the analytical expression of static voltage of wind power node is deduced,and the influence mechanism of static voltage stability of wind power node is analysed.The time domain simulation method is used to study the influence mode of wind power penetration,fault time,fault location and other factors on the transient voltage stability of wind power node.Finally,according to the static voltage stability margin index based on PQ curve,the maximum wind penetration considering static voltage stability constraint is proposed combined with the study of static voltage influence mechanism,which provides the basis for the planning and maximum consumption of regional wind power.(2)Reactive voltage control strategy for the wind farm considering reactive power adequacy and terminal voltage balance.Firstly,the expression of the maximum reactive power regulation capacity of the wind turbine,namely reactive power adequacy,is derived under the full wind condition based on the mathematical model and operating characteristics of the wind turbine,so as to study the influence of wake effect on the reactive power adequacy of the wind farm.Then,based on the radiative topology equivalent model of wind farm,the voltage of the connection point and terminal voltage are expressed analytically,and the key factors affecting the voltage stability of connection point and terminal voltage balance are analysed.Finally,an adaptive gain reactive voltage control strategy for wind farm is proposed,which comprehensively considers the input wind speed and the electrical distance from the connection point of each wind turbine in the farm to regulate the voltage of connection point and terminal voltage.While supporting the connection point voltage,it maintains the balance of the terminal voltage in the wind farm,thereby improving the friendliness of wind power grid connection.(3)Voltage stability analysis of the power system with wind power based on the thevenin equivalent analytical method.Firstly,the active power and voltage control capabilities of the wind power are considered,and the equivalent model of wind power integration based on the injection current source is analyzed.Then,the system node types after wind power integration are classified.Based on the basic model of Thevenin equivalent,the analytical model of Thevenin equivalent for the power system with wind power is proposed,and the analytical expression of Thevenin equivalent parameters is deduced according to two kinds of equivalent methods,and the action mechanism of wind power integrated on Thevenin equivalent parameters is studied theoretically.Finally,the voltage stability criterion based on impedance mode ratio is calculated by using the analytical value of Thevenin equivalent impedance,and the process for judging the voltage stability of equivalent nodes of the system under different load growth ratios and different wind power penetration ratios is developed,so as to accurately evaluate the voltage stability of the power system with high proportion of wind power.