OPTIMAL OPERATION OF LARGE-SCALE POWER-SYSTEMS

A method for optimal operation of large-scale power systems is presented that it is similar to the one utilized by the Houston Lighting and Power Company. The main objective is to minimize the system fuel costs while maintaining an acceptable system performance in terms of limits on generator real and reactive power outputs, transformer tap settings, and bus voltage levels. Minimizing the fuel costs of such large-scale systems enhances the performance of optimal real power generator allocation and of optimal power flow that results in an economic dispatch. To handle large-scale systems of this nature, the problem is decomposed into a real and a reactive power optimization problem. The control variables are generator real power outputs for the real power optimization problem and generator reactive power outputs, compensating capacitors, and transformer tap settings for the reactive power optimization. The gradient projection method (GPM) is utilized to solve the optimization problems. It is an iterative procedure for finding an extremum of a function of several constraint variables without using penalty functions or Lagrange multipliers. Mathematical models are developed to represent the sensitivity relationships between dependent and control variables for both real- and reactive-power optimization procedures and thus eliminate the use of B-coefficients.