Voltage stability constrained optimal dispatch in deregulated power systems

Voltage stability is a challenging problem for independent system operators because of less regulation in power flow patterns and more intensive use of available transmission facilities in deregulated power systems. An equitable and effective scheme for rescheduling pool generation and adjusting contract transactions is proposed in order to ensure adequate voltage stability margin (VSM). A linear optimisation methodology with the objective of minimising the social benefit loss because of generation rescheduling and transaction curtailment is formulated with consideration of the static functional operating constraints and VSM requirements with respect to normal condition and contingencies, and then solved by a linear programming technique. Since the pattern of load increase is difficult to be predicted in new market environment, the system loadability of the locally closest bifurcation is computed and used as the VSM in the proposed method. The effectiveness of the proposed method has been verified using a modified 39-bus New England test system. A study on the effects of post-contingency corrective capability of the system on social benefit loss and voltage stability performance is also presented.