Research On Influence Of Integrated DFIGs On Power System Transient Angle Stability

Under my country’s fast-developing economic system,the energy crisis and the deterioration of the environment have posed a great threat to us.As one of renewable clean energy,the development prospect of wind energy is very good.In recent years,wind power generation has attracted great attention among the new power generation technologies.At the same time,the scale of power system is becoming larger and larger.With the introduction of a series of new power equipment,the stability of the power system becomes more prominent.The large-scale introduction of doubly-fed induction generator into the power system will undoubtedly lead to the transient stability of the power system.Therefore,the influence of grid connection of doubly-fed induction generator on power system transient angle stability is deeply studied in this thesis.This thesis studies the influence of grid connection of doubly-fed induction generator on power system transient angle stability.According to the transient characteristics of doubly-fed induction generator,an impedance equivalent model and a controlled current source equivalent model based on doubly-fed wind turbines are established,and the influence of grid connection of doubly-fed induction generator transient power angle stability of power system is analyzed.The main research contents of this thesis are as follows:The influence of grid connection of doubly-fed induction generator on power system transient angle stability under symmetrical and asymmetrical faults is analyzed.The extended single machine infinite bus system for grid connection of doubly-fed induction generator,establish impedance equivalent models of doubly-fed induction generator under symmetrical faults and asymmetrical faults respectively.Based on the law of equal area to determine the theoretical method of grid connection of doubly-fed induction generator to the system transient power angle stability analysis.With the change trend of the four influencing factors such as the proportion of wind power,grid connection position of the doubly-fed induction generator,the fault location,and the load access position.The influence laws of the above four factors on the transient power angle stability of power system are summarized.In the analysis of asymmetric fault,different types of doubly-fed induction generators are selected to the applicability of the influence law.In PSD-BPA,the simulation model of extended single machine infinite bus system of doubly-fed induction generator under symmetrical fault and asymmetric fault is established,and verify the accuracy and validity of its theoretical analysis.Influence of doubly-fed induction generator participating in system frequency modulation on power system transient angle stability.Extended dual machine system for grid connection of doubly-fed induction generator,the doubly-fed induction generator are equivalent to a controlled current source model.Based on the law of equal area to determine the theoretical method of integrated doubly-fed induction generator to the system transient power angle stability analysis.The limit cut-off angle under different influencing factors is deduced in detail,the influence laws of the above four factors on the transient power angle stability of power system are summarized,and the grid-connected doubly-fed induction generator has an impact on the power system under the two conditions of whether the wind turbine is involved in the system frequency modulation.In PSD-BPA,before and after the doubly-fed induction generator participates in the system frequency regulation,the extended dual machine system simulation model of grid connection of doubly-fed induction generator is established,and the accuracy of the theoretical analysis was verified.