Closure to discussion of "voltage stability analysis: V-Q power flow simulation versus dynamic simulation"

Abstract

of each allele represents the number of blocks of fixed capacity that are being added to the existing circuit. The representation of other situations, such as replacing the existing circuit for another one with different technology, or different voltage, would require the use of more than one allele for the respective circuit (let call them as “sub-alleles”) as well as the implementation of a rule that tells the GA to turn off the effect of one sub-allele to let the other take place. For instance, if one wants to analyze the expansion of a given circuit at two different voltage levels, say 230 kV and 500 kV, two sub-alleles should be set up: one representing the number of blocks of expansion at 230 kV and the other at 500 kV. The aforementioned rule should ask the GA to fix to zero either one of the sub-alleles to let the other influence in the chromosome’s fitness. Even though we did not implement such an option, we believe that it can be successful. Concerning the second issue, even though a GA for finding optimum dynamic expansion plans could be developed and implemented, it should be mentioned that considering the uncertainties, the amount of information that is no longer available for the public and the decentralization of decisions in a competitive market of electricity supply, the effort of implementing a GA-based, dynamic expansion model, would not be worthwhile. In our opinion, the dynamic of the expansion (dating of new installations) is defined by complementary studies such as stability and reliability assessment and short-circuit analysis. However, among the set methodologies, methods and programs for the expansion planning, a static integer transmission expansion model is necessary to pick up major interconnections and facilities that will be present in most of the scenarios. A short-run, market-driven expansion model will never foresee those large-scale projects. Regarding the third issue, in a market based on physical bilateral contracts with short-term transactions, the long-term view about the problem should be replaced by a short-term view, whose emphasis is to manage congestion through prices. Nevertheless, if the interest is focused on the long-term analysis of the transmission expansion under such a market of contracts, a GA-based algorithm could be used, if multiple scenarios of load, dispatch and bilateral transactions are considered.