Middle And Long Term Voltage Stability Analysis And Emergency Control Studying Combined With Power System Partition

Throughout the development process of the power system, the network reflected different characteristics at different stages. For example, in the early stage of power system, the network mainly performed the angle and frequency problems because of its weak grid structure. However, with the rapid development of power system, the structure of grid was optimized to strengthen, and the size of system was expanded. These work made the power system step into period of saturation. For the time beginning, the problem of voltage stability highlighted. Now, the trend of development of China is power system interconnection. It can promote the exchange of the regional grid and make the energy be fully used. However, it will also bring many negative effects. Not only can it exacerbate the complexity of the system but also it can greatly increase the probability of voltage instability incidents.At present, China’s electric power workers have been achieved fruitful results in the static, small interfering and transient voltage stability analysis. But we haven’t carried out depth research in middle and long term voltage stability field. Especially for voltage emergency control, there is not mature theory used into practice as the most important means to prevent voltage collapse. Therefore, studying of middle and long term voltage instability mechanisation, and completing theory of voltage emergency control, have significant meaning in research and practical applications.Firstly this paper explains the significance and the main content of the voltage stability studies. Then it analyses the current research status about voltage stability and emergency control and points out the direction and main content of the studies.The middle and long term voltage stability problem demonstrates typical slow-dynamic characteristics. Combining with quasi steady state (QSS) simulation ideas, this paper establishes the QSS simulation model by ignoring the fast transient progress. Meanwhile, it also analyses the general progress of middle and long term voltage instability on the Dymola, which is good at modeling and simulating. In addition to, it observes the influence of continuous and discrete measures to voltage stability. The model of studying middle and long term voltage stability also turns out to be right and applicative.In recent years, people has also made breakthrough in the voltage emergency control field. MPC (Model Predictive Control), which is an online rolling-horizontal optimization method, is the most suitable method to study voltage control. MPC requires a lower level of mathematical model. Besides, it can correct the error after each rolling-horizontal optimization on the basis of the actual control. So MPC can adapt to the variability of the complex power system. However, traditional MPC is centralized control technology. Its optimization speed is hard to meet the online requirement for large-scale systems. Therefore, this paper uses fuzzy clustering analysis method to partition the power system. This method reduces the solution scale and improves the control flexibility ratio. Then this paper combines Dymola and Matlab, and realizes the optimization control process by programming in this platform. At last, the paper verifies this method’s veracity and rapidity in the39-nodes system.