Impact of the transformer tap-ratio control on the electricity market equilibrium

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In this paper, the primal-dual nonlinear interior point method has been used as a basis for the derivation of a novel supply function equilibrium (SFE) algorithm for modeling the strategic interactions in the electricity market, using the ac network model, which incorporates modeling of the transformer tap-ratio control. The algorithm is used to investigate the impact of transformer tap-ratio control on the electricity market equilibrium and the effect of the interactions between network constraints and transformer tap-ratio control. The interior point social welfare optimization problem is combined with the optimization problem for maximizing the profit of each strategic generating firm in the market. The final combined single-level SFE problem is solved iteratively based on solution techniques of the interior point method. Numerical examples illustrate the effect of network constraints and especially the impact of transformer tap-ratio control on market equilibrium.


Original languageEnglish
Pages (from-to)65-75
Number of pages11
JournalIEEE Transactions on Power Systems
Issue number1
Publication statusPublished - 1 Feb 2008


  • power systems, interior point algorithm, power transmission economics, power transformers, power system economics, electricity market equilibrium, AC network modeling, supply function equilibrium, market power, power generation economics, transformer control, power system modeling