Research On Power System Static Security Risk Assessment Method

Electric power industry is the foundation of the national economy. Secure and stable operation of the power system is the major premise guarantee of the economic development, social progress and national security. Modern society's unceasing development prompts burgeoning of electricity demand. The scale of the power system is increasingly expanding, and it presents the trend of large power system's interconnection. This brings huge economic benefits, and in the meanwhile produces a series of security and stability problems to the power system. It is of important significance for the secure and stable operation of the power system to establish a set of real-time effective online safety assessment warning system and preventive control and decision support system.This paper thoroughly discusses static security analysis of the power system using risk assessment method which based on the risk theory. It not only can consider the uncertainty factors of the system, but can combine the probability and consequences of the accident occurrence as well. By establishing the probability model of network components, taking the influences of uncertain factors in the power system into consideration (including uncertainty of generator outputs, uncertainty of system loads and electrical equipment failure, etc.), this paper applies probabilistic load flow(PLF) and semi-invariant to analyse the uncertainty of the system operation and the uncertainty of the line flow they caused. Then establishes risk assessment indices for line overload and voltage security, and quantificationally analyzes the static security risk of the power system. From these, the dispatchers can sufficiently understand the operation condition of the system and make the key link clear. Finally, in order to improve the operation safety of the power system, according to the grid risk minimization goal, through genetic algorithm provides the reasonable risk prevention and control strategy.This paper uses two semi-invariant based PLF methodes. One is Gram-Charlier expansion theory based on semi-invariant, and the other is the method proposed in this paper which combines the semi-invariant and improved Von Mises method. And the two methods calculation results are also analyzed and compared. In order to reflect the real-time security situation of the grid more accurately, anticipated accident list based on the current operating condition that is influenced by the uneven distribution of time and territory domain is constructed, and combines the total probability theory with PLF, a probabilistic load flow algorithm considering static security risk of power system is proposed in this paper. The calculation on the IEEE RTS 96-node test system indicates that this algorithm can effectively reflect the operation risk of the power system. Simutaneously, on account of the influence of the grid operation safety caused by the stochastic capacity and intermittent fluctuation new energy produced, this paper establishes steady-state probability model of the wind-driven generator, analyses the impact of the operating characteristics of the power system after wind turbine insertion, and explores the technical requirements of wind power generator's sychronization and operation.