Research And Development Of Power System Voltage Stability Assessment System

Seventies in the last century, there were several power utilities related to voltage instability in the world, and the instability resulted in large economic loss and significant social influence. After that, the study of voltage stability has gradually become experts and scholars' concerns, but compared to the study of power angle stability, the study of voltage stability is still not enough depth.With the rapid development of our country's economy, power grid construction has become more urgent. There has raised some new challenges at the some time meet the balance between supply and demand for the grid. With the huge interconnected power network, many complex dynamic phenomena appear in operation and the destructions caused by voltage instability have a great affect on the whole society and the national economy. So we should search for a method which can assess the voltage stability of a power system quickly and accurately. The main work and contents of this thesis are as follows:In this thesis, we summarize the definition of voltage stability, the classification of voltage stability, the mechanism of voltage collapse and the content of voltage stability's analysis. We introduce several commonly used static and dynamic voltage stability analysis methods, and introduce several representative voltage stability indexes in detail.Voltage instability often starts from a weak load node or a weak area of the power system, and generally spreads to the entire system, and results in the voltage landing or even voltage collapse. According to the nature, we use local voltage stability index L to determine the weak load nodes, and the load nodes constitute a set of weak load node.The whole power system can be seen as a collection of power transmission paths. Although power transmission paths are very complex in practical power systems, the voltage stability degree of power systems can be represented by the voltage stability of the power transmission path which is the most prone to voltage instability due to the local nature of voltage instability problems. So we can find the weakest power transmission path first, and then obtain the index of voltage stability with the equivalent of the transmission path. With regard to the complexity of actual systems, this thesis uses the local voltage stability to search the weak load nodes. Then, we search the participative nodes and key power sources with the directions of the actual power flow which gain from the power flow calculation. Those participative nodes and key power sources can make up the transmission paths set, and it is easy to calculate the voltage stability index of a transmission path and key generator reactive power reserves.On the base of this method, we produce software to assess the voltage stability of a power system with Visual C++. The users can calculate the common power flow and the voltage stability of a power system. The software can provide the list of weak load nodes, system weak path, and reactive power reserve of the key generators for the users. The simulation results of the New England test system demonstrate that the accuracy and interoperability of the system is very satisfactory.At last, we use the software to assess the voltage stability of the Shandong electrical network.