Abstarct: In this thesis, Volt-Var optimization (VVO) as useful tools for distribution system operator schedules reactive sources to minimize the cost of power losses and maintain voltages within their admissible range. Taking the advantage of smart grid infrastructure, the schedules are decided near the time of power delivery. baxsed on the real-world data, active and reactive power loads are presented through voltage-dependent models. Additionally, uncertainties in power load and renewable sources are presented by two different uncertainty models: i) a single-scenario forecast, and ii) prediction intervals. The VVO problem is converted into deterministic and robust optimization (RO) models by the former and latter uncertainty models, respectively. These two VVO models are implemented in 14- and 69-bus test systems and their results are compared. The results indicate that the schedules made by the RO model is more feasible in practice, but with higher cost.