This work presents a computational method for the simulation of wind speeds and for the calculation of the statistical distributions of wind farm (WF) power curves, where wake effects and terrain features are taken into consideration. A three-parameter (3-P) Logistic function is used to represent wind turbine (WT) power curve. Wake effects are simulated by means of Jensen’s wake model. Wind shear effect is used to simulate the influence of the terrain for WTs located on different altitudes. An analytical method is employed for deriving the probability density function (PDF) of the WF power output, based on the Weibull distribution for describing the cumulative wind speed behavior. The WF power curves for the cases of four types of terrain slopes are analyzed. Finally, simulations with the help of the Monte Carlo method with different sample sizes are provided to validate the proposed model. The simulation results indicate that this approximated formulation can be a kind of substitute for WF output power estimation especially for the scenario where WTs are built on a terrain with gradient.