An Enhanced Numerical Discretization Method for Transient Stability Constrained Optimal Power Flow

Although many efforts have been made in past years, transient stability constrained optimal power flow (TSOPF) remains one of the most difficult problems in power system. A popular approach to deal with transient stability constraints is the numerical discretization method, in which TSOPF is converted to a generalized large-scale nonlinear programming problem, and interior point method is preferred to solve it. In the numerical discretization and interior point method based TSOPF, more than 80%-90% CPU seconds are used in solving the primal-dual linear system. In order to improve the computational efficiency of numerical discretization TSOPF, an enhanced numerical discretization method is proposed in this paper. The key enhancement of the proposed approach is: considering the truncation error of specific numerical integration algorithm, the transient differential equations are discretized to inequality constraints instead of equality constraints. This key enhancement reduces nearly 50% of the primal-dual linear system´s dimension and greatly improves the computational efficiency of interior point based TSOPF algorithm. Case studies on several test cases up to 678-bus system indicate that the enhanced approach is much more computationally efficient than the conventional numerical discretization method and is promising to solve larger TSOPF problems.