Researches On Voltage Stability In Power System Based On PSS/E

Voltage stability analysis is one of the important subjects in modern power system research, which greatly extends the connotation of power system stability. For a long time, people have carried out a large amount of research on the rotor angle stability, clarified the mechanism of angle instability, and set up a relatively mature theory of analysis and control that widely used in the power system. But the mechanism of the voltage instability or collapse are still not at all clear as compare with that of the rotor angle instability. Not only the relations of voltage instability to rotor angle stability have not established, but also the relatively intact analysis and control theory of voltage stability have not set up. This dissertation, has carried on the research in mechanism, analytical methods and influence factors of voltage stability on the basis of summarizing forefathers' research results, focus on the following two respects, and has made some progress in application.Determine the voltage stability limit is an important job for the static voltage stability research. At present, there are many algorithms for computing the voltage stability limit, but the existed problem in them is the high computation burden. It is necessary to improve the algorithm. Power system analysis and computation technology entered a new era with the help of the comprehensive power system simulation packages. PSS/E supply a user-defined language-IPLAN, which can make it possible to realize the computation of voltage stability limit. A method, which is for computing the voltage stability limit based on PSS/E, is presented in this dissertation. This method, adopting admittance model in load bus and using the activities supplied by PSS/E, can compute the voltage stability limit effectively. The difficulties connected with the singular load flow Jacobian matrix are overcame in this algorithm. Moreover, this algorithm is simpler for application, faster in calculation and clearer on physical conception than other algorithms. The effectiveness of this method is examined and proved in some standard IEEE nodes network.Referring to the longer-term (mid-term and long-term) course is the characteristic of voltage stability. According to time, voltage stability can be divided into longer-term voltage stability and transient voltage stability. It is necessary to carry out dynamic simulation in the course of longer-term voltage stability analysis. In this dissertation, correlative research of longer-term voltage stability have been carried out, including some slow dynamic elements, such as On-load tap changer (OLTC), Maximum excitation limiters (MEL), etc. The effects of these slow dynamic elements on thecourse of voltage instability or collapse are revealed from the point of view of time-domain simulation. Studies were performed with the Extended Term Dynamics module in Power System Simulation (PSS/E) program. It shows that the action of On-line tap changer in the load bus has an important influence on the voltage stability of the system.