Dispatch of wind-thermal power system by using aggregated outputs of virtual power plants

Usage of renewable energy sources, such as wind power, is of major importance in future power grids for economic and environmental reasons, while the intermittent and stochastic nature of such energy brings challenges to system dispatch. Application of the virtual power plant (VPP) concept is one of the most promising ways to better accommodate and utilize renewable power in the grid. Among the many issues of applying VPPs in practice, the aggregated output characteristics of a VPP containing several wind and thermal generators have not been well studied yet. In this paper, a two-phase economic dispatch model considering the aggregated outputs of VPPs is presented for wind-thermal power systems. In phase 1, outputs of VPPs are decided by the grid operator, with characteristics of such VPPs obtained by aggregating those of individual generators. Then in phase 2, a local dispatch among individual generators within each VPPis performed by its aggregator. Both of the above two phase shave linear programming formulations, and numerical tests are performed on an illustrative 3-bus system. Results show that compared with conventional economic dispatch models, our model leads to substantial improvements in wind power utilization and lower generator costs.