Study On Voltage Stability Margin Based On The Value

In our country, the power system has entered a comprehensive system era, it has the characteristics of large units, ultra-high voltage, AC and DC power coexist and all kinds of distributed generations working in the same time. However, when this kind of power system bring the advantages of high efficient and intelligent, there also bring a series of problems and challenges to the electric power industry, such as the intermittent and randomness of distributed generations, harmonic of the interconnected power and other factors. It’s an arduous task that how to monitor and control the stability of the power system to ensure the power system operate safely and reliable in the face of the increasing complexity power system.Usually,the voltage instability of power system due to one or several weak nodes, then it can spread to the whole system gradually. In defense of power system voltage instability, it’s an important work that how to identify weak nodes of the system quickly and accurately. This paper proposed a ratio voltage stability margin index based on angle index and impedance model index. The proposed method based on the principle of maximum transmission power and using the Thevenin equivalent parameters to realize the online voltage stability margin calculation.Thevenin equivalent is an important method for the voltage stability studying of power system. The Thevenin equivalent parameters is based on the actual disturbance response of the power system, it can simplify the network accurately. The key problem of Thevenin equivalent is how to get more accurate Thevenin equivalent parameters. This paper through the analysis of the mothed based on system topology and the method based on total differential, and looking for a better method to obtain better Thevenin equivalent parameters, then obtain the voltage stability margin based on the obtained Thevenin equivalent parameters. Through the simulation of IEEE9 and IEEE39 bus system, the effectiveness of the proposed method has been proved.