Doubly-fed Wind Power Generator Voltage-reactive Power Control Method Of Research

With the increase of the scale of wind farm and wind turbine capacity, the mutual influence between wind farm and power grid gradually increased, the reactive power problem between systems are also increasingly prominent. At present most of the motor in doubly-fed wind farms are run under the mode of unit power factor, reactive power adjustment ability of doubly-fed motor itself has not been fully utilized. First, in the comprehensive analysis of the research background and research status quo, on the basis of doubly-fed motor was established by the mathematical model of steady state and transient. This paper analyzes the reactive characteristic of the doubly-fed motor, especially the reactive power capacity and limitation. In view of the grid voltage unbalance the analysis of the characteristics of doubly-fed motor output, it is concluded that the important role of reactive power on the system stability.Doubly-fed motor from the stator side and network side converter output reactive power, due to the stator side directly connected network, the stator voltage is constant value, and the stator reactive current mainly influenced by the rotor excitation current side. In reactive power control section of the doubly-fed motor is analyzed, based on the improved rotor excitation current controller. Reactive power imbalance caused by power grid voltage fluctuation, adjusting the rotor current change of the stator side output reactive current component to control the stator side output reactive power. But due to the rotor side excitation current and motor running state, control current has some limitations. So they are studied and analyzed the network side converter reactive features, it is concluded that the network side converter can run under the unit power factor, when the grid voltage fluctuation can adjust reactive part of the network side converter to provide power grid reactive power demand or doubly-fed motor itself.Finally, when the grid voltage fluctuation, in combination with doubly-fed motor rotor side and network side reactive power control strategy to provide reactive power needed by the system. And experiment in the Matlab/Simulink software, proves the feasibility of theory and reactive power control strategy. So wind farms can serve as an important reactive power in power grid, can not only stable doubly-fed motor output characteristic changes caused by power grid voltage fluctuation, and make full use of the reactive power regulating function of wind turbines, improve the utilization ratio and can also reduce power grid caused by reactive power imbalance is unstable.