Analysis And Optimal Control For Power System Static Voltage Stability Based On Interior Point Algorithm

With the rapid increasing of power energy demands in our country, and due to the fact that the speed of construction of power generation and power grid is relatively slow, voltage stability issues are becoming more and more severe and voltage collapse is now a big threat to power system. The power system operation and control technologies need to be improved because of the interconnection among large networks. At the same time, the stability margin is also more and more narrow resulting from the separation of grid from generation and price bidding. In addition, the rapid changes of power flow bring many requests for steady and secure operation of power system. As we know, the tighter electric connection is, the larger disturbance area is. So that a single accident may be transformed into an extremely serious fault, if effective control measure is not available, or functions of system operating and supervising are not mature or due to the fact that operators are lack of ability to anticipate the occurrence of voltage collapse. Therefore, the operator should conduct real- time supervision on the condition of system voltage and carry out countermeasures to sustain the secure voltage level in order to prevent power system from voltage collapse. Thus, the major work in this paper is based on the above facts.In this paper, based upon earlier work, two mathematical models for voltage stability margin calculation and voltage stability optimal control are established. And both of them have been analyzed and simulated explicitly with interior point method which is a nonlinear programming method. In the first model, a relative margin index of active load is introduced, and this index is used as the objective function for that model. The present approach has been compared with the existing CPF method, and the result shows that the accuracy and robustness of present method is pretty satisfying to operators. Furthermore, in this paper, voltage stability has been analyzed by CPF method considering dynamic processes of system components, and its results indicate more practical meaning. The optimal control model for voltage stability includes preventive control and corrective control models, both of which consider the smallest margin which steady operation requires. The results of these optimal calculations can satisfy the demands of system operation, which also improve the voltage stability of post- fault system. Furthermore, this optimal control system and AVC system have combined to maintain certain voltage stability and to strengthen voltage security by AVC executive equipment.In Fujian province, an online preventive control system for power system voltage stability has been developed, which includes voltage stability margin calculation and optimal control calculation. That program can figure out system voltage level and provide control measures to system operators so as to enhance voltage stability. Meanwhile, it can show the dispatchers system profiles. Currently, the approach presented in this paper works very well, and this time-tested program will show its power to the power industry.