Power System Transient Stability Analysis Based On Phase Trajectory Method And Considering Wind Power Grid Connection

As the scale of the power system continues to expand,the structure becomes more complex,and the power transmission between regions increases,the transient stability problem faces more challenges.In order to ensure the safe and stable operation of the system,it is particularly important to find a fast and accurate power system transient stability assessment method.In this paper,the following research work is carried out on the rapid assessment of transient stability margin of power system and its emergency control scheme:Firstly,based on the phase plane analysis theory,based on the correspondence between phase trajectory and transient stability,the single machine The infinity(OMIB,one machine infinite bus)system is used as an example to analyze the variation characteristics of the phase trajectory and convexity index in the transient process.It is found that the extreme value of the concave and convex index can quantitatively reflect the stability of the system,thus defining the basis Transient stability identification method for phase plane trajectory characteristics.And in order to increase the accuracy of the temporary stability identification,a supplementary criterion related to the system energy is proposed.Secondly,a quantitative cutting machine load shedding emergency control method is proposed to improve the transient stability of power systems.Based on the analysis of the interaction mechanism between power angle instability and voltage instability,considering the coupling relationship between voltage instability and power angle instability,the influence of voltage and power angle changes on power variation on key branches is analyzed.Based on this,the relationship between the cutting load ratio and the dominant mode of system instability is derived.According to the characteristics of the phase plane trajectory,the minimum quasi-cutting capacity of the system to restore the stable region to the stable region is analyzed and calculated.The amount of load shedding was obtained according to the degree of voltage drop.Based on the relationship between the system instability mode and the minimum cutting capacity and load shedding,the cutting machine load shedding scheme of the multi-machine system is comprehensively obtained.Then,considering the influence of doubly fed fan(DFIG)access on the transient stability of power system,the large capacity of renewable energy is connected to the power system.The fan is connected to the power system in the form of negative impedance;then,according to the power flow equation of the system,the electromagnetic power characteristic curve of the two-area generator is obtained and further equivalent to the single-area electromagnetic power;the equivalent mechanical power of the two-area synchronous machine is obtained according to the difference of the wind power access amount and the distribution rate of the two-area synchronous machine;and the network topology is considered from the principle of equal area.The influence of structure,wind power access location,ratio of inertia of two-area generator,output adjustment of two-area synchronous machine,wind power access amount and wind power electromagnetic power output during fault on system transient stability.Finally,because the random excitation of wind power will affect the stability of the system after it is connected to the system,this paper studies the limit of the influence of wind power random excitation on the system based on Taylor expansion method.