Transient Stability Constrained Optimal Power Flow Based on Multi-time Scale Power System Models

Abstract

This paper is focused on the transient stability constrained optimal power flow (TSC-OPF) problem and its application for determining the optimal dispatch of active and reactive powers of distributed synchronous generators. In order to relieve the mathematical complexity of the TSC-OPF problem with respect to its dimensionality, this paper proposes a decomposition of the power system model in a two-time scale model which is constituted by two smaller-order subsystems denoted by the fast and slow subsystems, where only the equations of the fast subsystem are transformed in algebraic equations by means of the implicit trapezoidal technique and incorporated in the TSC-OPF formulation. The TSC-OPF is then solved by considering in its formulation the lowest amount of time steps in post-fault period that guarantee the rotor angle first swing (FS) stability of the fast subsystem, and this aspect also contributes for reducing the dimensionality of the TSC-OPF problem. Tests were made for a 31-bus distribution network with two synchronous generators and for a 51-bus distribution network with nine synchronous generators.