System security enhancement against voltage collapse via coordinated control

In this paper, the problem of analytically coordinating dissimilar voltage control actions to prevent voltage collapse in a large power system is addressed. A framework for hybrid control based on coordination of controls with different response time and dynamic characteristics is presented. The proposed method is based on a security constrained steady-state approach. The minimum distance from the operating point to the bifurcation boundary is used to evaluate system security. The optimal corrective control direction towards adequate security is then obtained by calculating the sensitivity of the minimum distance with respect to controls. The actual dispatch of controls along the optimal direction, which takes into account impacts of economic cost and control availability, is determined as the solution of a multiple stage optimization problem using differential dynamic programming. The algorithm is demonstrated for a system with dynamic load models representing the main grid of the New South Wales, Australia.