Research On Voltage Stability Evaluation Methods Of Wind Power Integration

Distributed generation using renewable energy sources is preferred and rapidly developed by various countries, because of its advantages of energy conservation & environmental protection and flexibility & efficiency. However, the growing integration of new energy changes the one-way feature of energy flow in power grid, which significantly affects the voltage stability of current power grid. For example, with the integration of wind generation, the power grid is changed from the single power source system to the system of multiple power sources. Besides, it is also changed that the direction & quantity of power flow, the type of nodes, the voltage distribution. Meanwhile, due to the randomness of wind generation and the probability of unit faults, the reliability of power system is decreased. Therefore, in order to utilize the distributed generation more efficiently and to monitor & analyze the stability of power grid, it is necessary to find a voltage stability index suitable for power system with wind generation. In order to achieve the purpose of this thesis, the following work has been carried out:Summarize the features and application status of various types of distributed generation. Introduce the voltage stability in different stages and its classification. Explain the voltage instability from the perspectives of static and dynamic mechanisms, respectively. Analyze the advantages & disadvantages and the applicability of static and dynamic stability analysis methods, respectively, as well as the superiority & inferiority of state & margin indexes in different issues.Based on the impedance modulus margin proposed in the comprehensive dynamic analysis method for power system static voltage stability, firstly, the equivalent conversion is performed for the load model in power grid to achieve only the constant power load is included. Secondly, the impedance modulus margin is computed by the equivalent model. Because, the voltage of load node is invariant after the equivalent conversion, the impedance modulus margin of equivalent model can reflect the voltage stability of the original model. A stability assessment algorithm for wind integration is proposed, based on the impedance modulus margin index, which can real-time monitor the voltage stability of load nodes in whole power grid and take different solutions according to the value of the impedance modulus margin index. By means of simulation and engineering application, it is indicated that the voltage stability assessment method based on the impedance modulus margin can be used to realize the real-time, rapid and accurate evaluation of the voltage stability of power grid.