Investigation Of Transient Control Startegy For Power System With Large-scale Wind Power

In rencent years, China has built a batch of million kilowatt wind power base, and the utilization of wind power is centrailized and large-scale. Large-scale wind power integration to the power system brought a series of influence and change the original characteristic of the system, which includes the stransient stability of power system. The fluctuation of the wind power and the transient characteristics of the wind power generator make the transient characteristics of the system change, and have some effect on the safe and stable operation of the system. Therefore, the study of what transient control strategy the power system in the case of large scale wind power integration should take has important significance.Firstly, based on the wind farm model composed of doubly fed induction wind turbine, the influence of large scale wind power integration on the transient stablity of power system is studied. The wind power integration brings some uncertainty, the active power output fluctuation and demand for reactive power could have adverse effects on the system transient stability.Based on this, the control strategy of improving the transient voltage characteristic of wind farm is studied. Based on the analysis of the doubly fed induction wind turbine reactive power output potential, the use of grid side converter with pitch control is studied as the transient voltage control strategy of the wind turbine during a fault. And the control strategy of SVG in the wind farm is studied. The coordinated control strategy of the two reduces the voltage sag of the wind farm outlet bus during the failure of the gid, and the simulation proved the effectiveness of the control strategy.Secondly, aiming at the emergency situation of wind power and thermal power coexist system when a failure happen, the cutting machine is adopted to maintain the stability of the system. Analysis shows that the scheme making in the cutting machine object choice not only should consider the thermal power, but also should take wind power into account, so a cutting machine scheme considering both wind power and thermal power is put forward. The scheme in the premise of ensuring the stability of the system and to the thermal power cut acpacity reduction as the goal, through comparison of output level arranging wind power to enter the cutting machine table, develops appropriate wind power and thermal power tripping proportion. The simulation in two examples verified the effectiveness and feasibility of the proposed scheme.Finally the frequent domestic large scale wind off the net phenomenon is analyzed, using the simulation to reproduce the process of off grid, and the reason mainly lies in the lack of low voltage ride through ability for the unit and the poor reative power management of wind farm. Accordingly, the countermeasures for prevention of large-scale wind power off grid is proposed, which improve the operation ability of large-scale wind power base.