Research Of Voltage Stability Of Power Network Containing Wind Farms

Wind energy is a non-polluting, renewable green clean energy and also a kind of new energy that possesses the absolute advantages of scale development and commercial development. In recent years, wind power technology has been developed rapidly, its level and scale of development has considerably increased. The impact of wind farms on the grid has attracted more and more attention with the occurrence of the large-scale wind farm integration.In this paper, the mathematical models of the wind speed, wind turbine were built first; the dynamic mathematical models of double-fed induction generator (DFIG) under the ABC stationary coordinate system and the dq synchronous rotating coordinate system were deduced to laid a theoretical foundation for the modeling work of the double-fed induction generator unit.Based on the mathematical model of the PWM converter,control strategy of the grid-side converter directed by the grid voltage and control strategy of the rotor-side converter directed by the stator flux were established combining the vector control theory. All-digital electromagnetic transient simulation model of the DFIG unit was built relying on the real-time digital simulation system, the simulation results under fault conditions were basically consistent with the measured results, thus proving the fact that the DFIG model built in the real-time digital simulation system can truly reflect the operation features of the actual system .The method using the nonlinear simplex algorithm to optimize the PI control parameters of the DFIG unit was first proposed, optimization results proved that this method had good practicality and robustness.Regional power grid model containing wind power generators was built for the first time relying on the real-time digital simulation system RTDS. The fact that the Thevenin equivalent voltage stability index is only suitable for the conditions when the load can be ignored or increases by the constant power factor, not suitable for the transient voltage analysis under large disturbance is proved.