Study On Probabilistic Analysis And Control Of Power System Transient Stability

With the implement of interregional interconnection and the progress of power industry reform, power system security is playing an increasingly important part. However, power system is in nature a large one with random characteristics. In this sense, it is of theoretical and practical significance to take into account the impacts of statistical factors in system security assessment.Starting from the normalized generators' equations of rotor motion with respect to the center of inertia of system and the concept of normalized transient energy function (NEF), the variation characteristic of the minimum of normalized transient kinetic energy (NKE) in the post-fault duration versus fault clearing time has been studied. Utilizing the above characteristic, an approach named energy translation for assessment of transient stability energy margin (TEM) is proposed. The advantage of energy translation approach is that no identification of critical machine group is required in the evaluation of TEM. On the basis of the ideas of the energy translation and the conservation of NEF, a method to evaluate the capability for absorbing the component of NKE contributing to system separation is presented. Using the theory and approaches of NEF, the software for auto-computation of power system operation mode is developed. It has been applied in many power grids, such as Tianjin power grid, Henan power grid, Hebei power grid and Hong Kong power grid, which greatly improves the precision and reliability of security analysis.By analyzing the statistical property of fault clearing time and the severity order of different types of faults, a probabilistic assessment strategy of transient stability based on the NEF method is suggested. In the analysis strategy, only a small part of system faults, which is severe needs to be carried on the computation, therefore the efficiency of probabilistc analysis could be enormously enhanced and the burden of transient stability computation is greatly lightened.According to the theory of risk-based security assessment (RBSA), a method for evaluating maximum beneficial total transfer capability (TTC) with transient stability constraints is proposed. Probabilities and impacts of system transient instability incurred by contingencies are both considered in the TTC assessment, and risk threshold value is able to be avoided during the risk decision-making process of the TTC. As a result, the optimal balance between the efficiency and security of power...