The installation of distributed generation (DG) introduces challenges to distribution systems operation. The distribution network operator needs to schedule DG outputs considering some constraints, such as DG characteristics, reactive power control mode of generators, automatic voltage regulation, compensator and power quality standard, etc. Based on an optimal power flow model, this paper proposes a dispatch model for DG embedded distribution systems. The model is proposed basing on energy prices, weather forecasting and load forecasting. The objective is to minimize the electricity supply cost of the distribution company. The proposed model is tested in the 33-buse system. The results show that DisCo's cost and losses of the distribution system can be reduced by enhancing system operation flexibility