Research On Stability Analysis And Control Strategy Of Time-varying Power System

With new energy of large scale connected to the grid and the implementation of Project "Interconnecting the whole country", a large-scale interconnected power grid is forming in our country. And the problem of operation and control is also more and more severe:the time variation of output of wind generator due to the change of wind speed and time variation of system structure due to cascading failure has become a major factor affecting the power system stability. Therefore, there is an urgent need for research on stability analysis and control strategy of time-varying power system. The main contribution of this paper is as follows:An analysis method of time-varying stability of power system considering time variation of wind speed and cascading failure respectively is proposed in this paper: 1) The analysis method considering time variation of wind speed is based on continuous Markov theory. Robust stochastic stability criterion of power system under the influence of time variation of wind speed is deduced and this criterion is effective and correct in discriminating power system stability without the limitations of single mode linear model.2) The analysis method considering cascading failure is based on discrete Markov theory. Robust stochastic stability method of power system under the influence of cascading failure is deduced and this method is effective in discriminating power system stability without the actual running track of system. Simulation results show the science and correctness of the above analysis methods of time-varying stability of power system.Based on the above method of discriminating stability, adaptive robust control strategy of time-varying power system considering time variation of wind speed based on continuous Markov and cascading failure based on discrete Markov theory is proposed respectively:1) Adaptive robust control strategy of time-varying power system considering time-variation of wind speed is based on continuous Markov robust stochastic stability criterion of power system, matching controller of each model in the collection of state model is solved, stochastic gradient method is used to do online identification of the system and weighted control based on weighted index is realized. This method can realize smooth-switch between controllers in fully consideration of coupling relationship of each model.2) Adaptive robust control strategy of time-varying power system considering cascading failure is based on discrete Markov stochastic stability criterion of power system, the minimum variance robust control theorem under discrete Markov system is deduced and adaptive control is realized with online identification of the system. Rapid and effective control can be done with this method in a wide range of operation states change of system. Simulation results show the above adaptive control strategy can realize effective control of the system and restrain oscillation rapidly.