On-line Voltage Stability Monitoring System Based Security Region

In the past decades, several disastrous blackouts caused by voltage instability have occurred around the world. More and more attentions have been paid on power system voltage stability study. The traditional approaches for voltage stability analysis are'point-wise'type. They perform power system voltage stability analysis by case by case simulation based on a pre-defined system operating condition and a pre-given contingency list. The simulation process is time-consuming so that'point-wise'methods are difficult to be applied in the on-line assessment. Further, few information on system security can be provided by such methods, which is essential for the operators to find appropriate preventive control strategies. Recently, a so-called'region-wise'method has drawn more concerns. It can provide systematic and global security information for the operators. After parameters fluctuating, it does not need to be calculated again so that it is very suitable for on-line stability assessment. In this thesis, an on-line voltage stability monitoring and assessment system is designed and developed based on the theory of voltage stability region on the interface power flow space (abbr. CVSR, cut-set voltage stability region). The system now is applying in the power grid of Liaoning province in China. Main works in this thesis are as following:1. The mainframe of the on-line voltage stability monitoring and assessment system is designed. It can be divided into two parts: foreground and background. The two parts are developed respectively and integrated together by raw data files. This scheme not only can guarantee the stability and reliability of the whole system but also can make it possible to maintain or upgrade one component independently.2. The background subsystem is developed. It includes the following calculation components: data conversion, CVSR calculation, interface thermal limit analysis, system voltage margin assessment. And it also stores and maintains all the system data. All components in the background are designed into individual programs and coded by ANSI C/C++. The aim is to guarantee the efficiency, stability and transplant ability of the background subsystem.3. The foreground subsystem is developed. It covers the following components: graphic user interface (GUI), result publishing, system setting and visualization. Qt technique is applied to develop an OS independent GUI. All widgets are designed into individual components and provided by dynamic link libraries (DLLs) to make graphic system more stable and expansible. Some 3D/2D visualizations based on Qt/OpenGL are developed to show the voltage stability information more vividly.4. The on-line monitoring and assessment system is applied to the Liaoning province power grid in Northeast China.