Research On Optimal Dispatch Of Electrical Power System With Renewable Energy Sources Integration Of Virtual Power Plants

In recent years,the energy crisis and environmental problems have become the important factors that restrict the sustainable development of economy and society in the world.Renewable energy sources,such as wind energy,are advantageous over traditional thermal generation both economically and environmentally,and it is an inevitable trend that power supplies need to rely on more and more renewables.However,the integration of random and intermittent renewable energies will carry new challenges in the secure and economic operation of power systems.Virtual power plant(VPP)can integrate large-scale geographically dispersed and various types of distributed renewable energies and loads effectively,break the boundaries between power side and load side and improve power supply reliability,it is an effective way to solve the problems that renewable energies were integrated into the grid.How to make full use of the aggregated output characteristics of VPP,and use these characteristics to improve renewable energy utilization are important and valuable research topics.Considering the renewable energy power system optimal scheduling problem with VPP,the scheduling model and the solutions of the strategy are in a great difference,when comparing with traditional ones.One specific performance is that there is little research or application in the aggregated output characteristics of VPP,which connected with different power units of the electric power dispatching process.And the other one is that research in both power side and load side has not been considered in traditional dispatch model,such as the demand flexibility and environmental benefits.To cope with the above problems,this paper carried out three aspects of research work.Firstly,against the problems when small scale renewable energies were connected to the grid.A two-phase economic dispatch model considering the aggregated VPPs is presented for wind-thermal power systems.In phase 1,outputs of VPPs consisting of several wind and thermal generators are decided by the grid operator,with characteristics of such VPPs obtained by aggregating those of individual generators.Then in phase 2,an output dispatch is performed among individual generators within each VPP by its aggregator.We analyze the impacts of aggregated output characteristics and operation strategies in a VPP.Analyses are made under different decision horizons and intervals by using practical wind power data.Results show that compared with conventional economic dispatch models,our model leads to substantial improvements in wind power utilization,and lower generator costs.Secondly,considering the diversity of generators aggregated in a VPP,this paper analyses the power generation cost of the distributed generator(DG)in the VPP.And a VPP optimal dispatch model with wind power,photovoltaic power,small hydropower and micro gas turbine is established.With the goal of actual output of VPP tracking planning output and minimizing generation and environmental cost of VPP in each period,the output power of the DG in the VPP is obtained by the simulation of laboratory data.Results show that with the environmental benefits and reasonable operation strategies,the involvement of VPP in the optimization of renewable energy power systems can reduce the effect of output fluctuations on the power grid and the total generation cost.Last but not least,against the different effect from power side and load side of operation strategies in a VPP,two different models were carried out on the basis of analyzing aggregated output characteristics of VPPs,respectively,generation cost and flexible demands.What's more,two different operation strategies were presented on the basis of analyzing different optimal objectives of VPPs,respectively,self-supply strategy and benefit maximization.For the maximum profit strategy,an operating strategy of VPP based on the time-of-use power price was designed.The output power of each energy resource of VPP is obtained by the particle swarm algorithm.The simulation results show that VPP based on time-of-use power price can get better economy and power quality through using pumped storage and energy storage battery for joint operation and load optimal dispatching when large scale renewable energy is connected to the grid.