On-line Security Assessment and Control of Interconnected Power Systems Using Sensitivity Concept

Summary

Algorithms have been proposed for solving the steady state security assessment and preventive rescheduling problems using the sensitivity concept. The assessment algorithm uses a linearized model obtained from the inverse of the Jacobian of the normal state and other sensitivity matrices. Starting from the normal state voltage profile, two’ sensitivity iterations’ and one partially decoupled Newton-Raphson (N-R) iteration are performed to obtain the post contingency state voltage solution of acceptable accuracy. The algorithm is 4 to 5 times faster computationally than that using the N-R method. The validity of the algorithm has been verified by applying it to a typical 20 bus power system for both single and multiple line outages. The algorithm for preventive rescheduling problem uses the same linearized model in a linear programming format to determine a corrective reschedule of generations and loads, satisfying all the line flow security constraints and the engineering constraints on controllable generations and correctable loads and minimising a suitable cost function. Because of the more accurate linearized model used in the algorithm, for most of the systems, a secure state may be obtained within about two iterations of the algorithm. For the 5 bus example used in the paper, only one iteration was needed to obtain a secure state.