Dynamic security-constrained rescheduling of power systems using trajectory sensitivities

In the deregulated environment of power systems, the transmission networks are often operated close to their maximum capacity to achieve transfer of power. Besides, the operators must operate the system to satisfy its dynamic stability constraints under credible contingencies. This paper provides a method using trajectory sensitivity to reschedule power generation to ensure system stability for a set of credible contingencies while satisfying its economic goal. System modeling issue is not a limiting concern in this method, and hence, the technique can be used as a preventive control scheme for system operators in real time.

I. Introduction

P REVENTIVE rescheduling of power systems subject to stability constraints for contingencies has been investigated for a number of years. The earliest work [1] investigated the maximum loadability problem followed by an investigation into interface flow across tie lines [2]. Both used the transient energy margin concept and its sensitivity to change in generation schedules. Since then, a number of papers have appeared along these lines by extending the criteria to include optimal power flow (OPF) which is logical [3] [4] [5]. The other approach is to include the stability constraints as part of the OPF problem by converting the differential equations into algebraic constraints [6], [7]. In this case, the system dynamics are represented as classical swing models. The transient energy function (TEF) approach is limited to cases where a closed form expression for the energy is available and is difficult in the case of hybrid systems such as systems with tap changers or systems containing flexible ac transmission systems (FACTS) devices.