Direct nonlinear primal-dual interior-point method for transient stability constrained optimal power flow

The modem deregulated environment has driven utilities around the world to operate their power systems closer to their stability boundary for better use of transmission networks. A new approach of transient-stability-constrained optimal power flow (OPF), which can be used for the maximising system efficiency without violating any transient-stability limits, is presented. With the technique of equivalent transformation, transient-stabihty constraints are incorporated into the conventional OPF formulation. Jacobian and Hessian matrices of the transient-stability constraints are derived for the application of the direct nonlinear primal-dual interior-point method with quadratic convergence. A novel concept referred to as the 'most effective section of transient-stability constraints' is introduced to reduce the massive calculation of the Jacobian and Hessian matrices of the stability constraints. The validity and the effectiveness of the proposed method have been fully verified on two test systems based on the WSCC 9-bus and UK 686-bus systems.