Research On Voltage Stability Of Power System Containing High Penetration Of Wind Power

With the increasing seriousness of environmental pollution and the gradual depletion of traditional fossil energy, the technology of power grid integrated with new energy dominated by wind power develops rapidly in all countries of the world. As the penetration rate of wind power increases, the range of influence caused by the wind power output in power grid has extended. In a power grid with large penetration of wind power, the load flow is changed, and the power on the transmission line and the inertia of the system are influenced by the operation of wind power. On account of special nature of wind power, the original voltage stability of power system is changed by the characteristics of wind turbines.The voltage stability influenced by wind power in the power systems with the increasing penetration of wind power is studied in this paper, and the main contents are as follows.1.The steady state models and dynamic models of the doubly-fed induction wind turbine are formulated, and the static and dynamic characteristics of wind turbines are studied theoretically. The clustering method based on wind speed and K-means algorithm is introduced and the method shows that a wind farm is equivalent to one wind machine by the average wind speed calculated in steady state and that several equivalent machines are needed in transient state. Through comparisons of external characteristic such as voltages and power between equivalent models and the actual wind farm, it proves that the precision of models in K-means method is beyond90%.2.The method of P-V and U-Q curves are used in analysis of quiescent voltage stability. Since the traditional P-V curves do not reflect the volatility of wind power, by calculating the static voltage stability limit in different kinds of wind power penetration and in the Hainan2015power grid, the safe operation region made of three-dimension P-V surface is established to represent the safety margin of wind farms. By means of index of sensitivity analysis, in both strong and weak systems, the impact on system voltage stability of the increasing penetration of wind power is analyzed considering different operating modes.3.The time-domain simulation is an effective method in the study of voltage stability problems. The supporting role doubly-fed wind turbines reveal on the transient voltage is inferred, and the impact of DFIG on transient voltage stability is analyzed and testified in the single machine infinite bus system. The influence on transient voltage stability by changing the wind power penetration rate is analyzed in simulation through the access of equivalent wind farms on the Hainan2015network. Combined with the expression of terminal voltage of wind turbine, the effect of wind power penetration, grounding resistance, short circuit location and the access forms on transient voltage stability is studied.