Combined active and reactive despatch. I. Problem formulation and solution algorithm

A fully coupled active-reactive despatch using linear programming is presented. The purpose of combined active and reactive despatch (CARD) is to achieve the overall objective of minimum generation cost and/or to improve other system parameters, subject to constraints that ensure system security. CARD allows a series of time steps to be considered. The duration of each time stage may be chosen so that despatching points occur at any critical points of the predicted load curve within the despatch period. The problem is expanded such that the linear program variables include the output at the end of each time step, with the objective function value integrated over all stages. System constraints are replicated at each time stage. Dynamic rate limits are also included. The reactive power despatch is regarded as static within each step, but is influenced by the generator active power rate of change limitations