Optimum Power Flow for Systems with Area Interchange Controls

In this paper, the hourly operating cost of an interconnected power system constrained by prescribed area interchanges is minimized. The scheduled area interchanges act as constraining equations in the economic optimization procedure. The hourly cost minimization is performed with respect to active and reactive generation and is subjected to constraints on voltage and power flows. This minimization is carried out under several assumptions, notably: optimum operation of some area k of the interconnected system, optimum economic operation of the whole system with the interchange constraints satisfied, and optimum operation of the whole system with the interchange constraints disregarded for increased overall economy. These three assumptions are encountered in the operation of power pools. A numerical example involving a 30-node system, real and reactive power with adjustable transformers and three areas is solved by two optimization procedures: the Penalty Function method and the Generalized Reduced Gradient. A system equivalent that includes the effect of the area interchange controllers upon the flow is developed.