Abstarct: In this thesis, the effect of generation technologies on market power is studied from a structural perspective in a short-term period. The technological features of thermal power plants, such as upper and lower production limits, ramp up and down rates, and minimum up and down times are considered. Additionally, wind production uncertainty is modeled with considering spatio-temporal correlation among wind farms. In order to evaluate structural market power, market concentration problem is solved. This problem seeks to minimize and maximize market concentration measure, while considering operational constraints of a day-ahead market clearing problem. The nonlinear optimization problem is transformed into a mixed-integer linear programming problem. Using this simulation tool, the effect of generation ownership structure, technical characteristics of power plants and network constraints on market power is assessed. The results drawn from an illustrative example and a case study are presented and discussed.