A GENERAL OVERVIEW OF MULTIPLE OBJECTIVE OPTIMAL POWER FLOW IN HYDROTHERMAL ELECTRIC-POWER SYSTEMS

The minimum loss formulation of the optimal hydro-thermal power flow in electric power systems has recently been introduced and compared with the original formulation of optimal hydro-thermal power flow designed to minimize the total operating costs of the system. A few publications have addressed the latter, using Newton's approach employing the polar coordinates. A formulation of optimal hydro-thermal power flow in electric power systems combining the minimum loss objective with the more conventional minimum fuel cost objective is considered in this paper. The computational implementation is based on a Newton's iterative procedure, with special initial guess and sparsity-based matrix manipulations to obtain improved convergence properties. The strategies are developed using three standard test systems. We discuss the question of assigning an equivalent cost to the loss objective component and compare results obtained using two proposed mechanisms. The first is based on results of conventional dispatch using Kron's loss formula and the second uses the bus incremental costs involved in the OPF solution. The effects of varying the relative weights assigned to each objective component on pertinent system variables such as active and reactive power generations as well as voltages are explored.