An enhanced approach for probabilistic evaluation of transient stability

Due to the high penetration of renewable energy resources leading to the enhancement of uncertainty, the probabilistic assessment of the transient stability has become more important than deterministic assessment. In a previous method published by the authors, an algorithm to find the probability density function of the transient stability margin of the power system was published. This present paper presents a modified algorithm to find the probability density function of critical clearing time for each generator for the whole power grid for a certain contingency and during the fault-on period. First, the critical corrected kinetic energy is calculated based on a modified sensitivity-based algorithm at each step of the simulation during the fault-on period. Since the total kinetic energy of the generators does not contribute in the critical kinetic energy of the whole system, a new criterion - based on the rate of change of kinetic energy - is utilized to classify severely disturbed generators from less disturbed generators. Utilizing critical corrected kinetic energy of the whole power grid, an index based on the critical clearing time, so-called network critical clearing time, is calculated. Eventually, the proposed algorithm is applied on the optimal placement of a superconducting magnetic energy storage unit. It is shown that utilizing the proposed objective function for locating superconducting magnetic energy storage units effectively results in the improvement of the transient stability margin of the power system.