Research On Power Grid Of Voltage Stability Analysis

There have been many voltage instability accidents that happened to the local power systems and the state power system within the last few years. Therefore, subjects around the voltage stability such as the mechanism of voltage instability, the indexes of voltage stability, the strategy to avoid the voltage instability and so on, have drawn much attention of researchers. Currently, Shandong power grid (SDPG) is being interconnected with the emphasis on transferring large amount of power from the west region to the east. In operation, SDPG shows complex dynamic phenomenon. Therefore, it is necessary to develop new methods for voltage stability assessment and suggest measures to prevent voltage instability according to the practical operation of power systems. It is of great significance to prevent voltage instability of power systems and improve the reliability of transmission networks.To solve the problem of voltage instability of SDPG, the PSASP analytical tools are used to assess the static and transient voltage stability for SDPG. First, the influence of the load characteristic to the power system voltage stability is analyzed. The load models are identifid for the static and transient voltage stability respectively. Then, the voltage stability of SDPG is analyzed with static voltage stability analysis method and dynamic time-domain simulation. The problems of SDPG about voltage stability are pointed out. Measures to prevent voltage instability are suggested for SDPG.The main works of this thesis are listed as following:1. It elaborates the significance of the research on the voltage stability, the definition and classification of the voltage stability, the development and the current situation about the mechanism of the voltage instability and the analysis methods.2. It describes the existing voltage stability static analysis methods, including continuation power flow method, sensitivity analysis method and so on. Moreover, a method, which can evaluate static voltage stability taking account of the dynamic characteristic of the load and the dynamic element, is recommended. This part lays the foundation for the work of theory research and engineering analysis.3. Based on Thevenin theory, the whole system can be equivalent to a simple 2-bus system. On this basis, the influence of the static load characteristic to the power system voltage stability analysis is evaluated.4. Considering the influence of dynamic load models and parameters in simulation, the voltage stability of 2006 Shandong power system after the increase of load demand and the big disturbance in load center is analyzed and compared with the result based on the original data.5. By use of regional load margin analysis method, the static voltage stability of SDPG using the constant power model under basic operation mode in 2008 is studied. The regional active load margin index is defined and the sensitivity analysis for the influence of N-1 outages of 500 KV AC transmission lines on this index is carried out. The weak region of voltage security and the key transmission lines which mostly influence load margin are identified. A detail voltage stability analysis of the weak region is made, which uses sensitivity index to determine the weak buses of these areas. On this basis, the general measures for improving steady state voltage stability are suggested and analyzed.6. According to the construction of SDPG in 2008, this thesis analyses transient voltage stability in large-scale power system, researchs transient power transfer capability from the west to the east. What's more, the enhancement of voltage stability of SDPG, through static var compensator (SVC) providing dynamic reactive power support, is studied.