In-line with smart-grid developments, the need for performing lengthy time domain simulations with intermittent power generation as well as the associated control is crucial. Due to complexity and integrity of practical power systems, it is not practical to analyze them using exact time domain models. In this paper, a new method using quasi-static time-series (QSTS) concept is developed to achieve such simulations. The method assumes transition from one steady-state solution to another during the simulated time frame. The application of this methodology in transmission systems requires optimized control models to be included with the core power-flow engine. Classical power-flow is formulated to account for frequency variation during simulation. Hence, frequency has been introduced as a state variable to account for load frequency control (LFC). Fast economic dispatch (ED), based on loss formula, is integrated to ensure optimized energy supply during the simulation. In a narrow time-frame, between ED and LFC action, participation factors have been incorporated to allocate the small variations of demand among generating units. Wind power penetration is considered with 30% of the energy generation. Numerical results of a day-ahead load curve and wind power profile have been analyzed in a scenario of congested transmission system. The results show the effect of wind power variation in both frequency and other generating units. Moreover, the wind intermittency results in severe fluctuations in system frequency.