A Pseudo Spot Price Algorithm Applied to Short-Term Hydrothermal Scheduling Problem

Abstract

In this paper, a lossy electric power system, which contains thermal and hydraulic units, is considered. The total cost of thermal units in an operation period is minimized under some possible electric and hydraulic constraints. The operation period is divided into time intervals where the system loads are assumed to remain constant. The proposed technique has two main parts. In the first part (outer loop), pseudo active generation incremental cost values of hydraulic units are determined according to their respective water usage. In the second part, active generations in all time intervals are determined by using units' active generation incremental costs and pseudo spot price of bought active powers. Calculation of active flow of transmission lines, which are used in the determination of optimal active generations, are obtained by means of Newton-Raphson AC load flow analysis. The proposed dispatch technique considers minimum and maximum reservoir volume constraints, starting and ending reservoir volume constraints, upper and lower active generation constraints of generating units, and maximum transmission capability of transmission lines in a lossy power system. W e tested our proposed technique on an example power system. W e solved the same dispatch problem by using another dispatch technique based on gradient method, and results obtained from both techniques are compared.