Robust approach for capacity benefit margin computation with wind energy consideration for large multi-area power systems

Abstract

Capacity benefit margin (CBM) represents the tie-lines transfer capability margin for power interchange between interconnected areas. Accurate evaluation of CBM is essential for available transfer capability (ATC) determination. Most of the existing methods for CBM computation rely on complex optimization techniques. In these techniques, for every step increase in power transfer, to improve supply reliability of the deficient areas, the reliability must be recalculated and checked through optimization. Thus, for a large number of interconnected areas, these techniques might not scale well. Another shortcoming of these techniques is the simplifying assumption of only one deficient area with a fully connected network (i.e., all the areas have a direct connection or tie line with each other). In this thesis, a robust graph-theoretic approach is proposed to calculate CBM in a multi-area network with multiple deficient non-directly connected areas. Unlike the existing approaches, multiple deficient areas are considered and some of the areas are not fully connected. From literature, previous techniques only considered conventional generating units in the loss of load expectation (LOLE) computation. A strategy for the incorporation of wind power generating unit is proposed using Weibull probability distribution. This is important since the supply reliability of an area is measured using LOLE of the area and considering the random nature of wind generating systems which has a great effect on the supply reliability. In addition, LOLE which is commonly used as an index for the CBM computation is usually evaluated by using the area peak load demand and the available reserve capacity. The system peak demand usually occurs within a few weeks in a year; therefore, the period of off-peak demand is not efficiently accounted for in the LOLE evaluation. Hence, demand side management (DSM) resources; peak clipping and valley filling are employed to modify the chronological load model of the system which subsequently enhances the CBM quantification. Finally, the results of the CBM are incorporated in ATC computation to study the influence on the ATC evaluation. The proposed technique has been evaluated using IEEE RTS-96 test system because the system has all the required reliability data for LOLE computation. The technique can evaluate and allocate CBM among multi-area systems consisting of two deficient areas. The influence of renewable energy on LOLE has been efficiently evaluated and the DSM technique was efficiently employed to improve three-area test system generation reliability. The generation reliability of the interconnected areas has been improved by an average of 35%. This improvement is very significant in terms of the generation facilities and the financial implication that may be required to be put in place if the proposed DSM technique was not applied. The results and the performance evaluation showed that the proposed technique is simple and robust compared to the existing methods. The technique can also be used as a feasibility tool by utilities to verify the possibility of wheeling power to a deficient area using maximum flow algorithm.