Optimal Scheduling Method For Active Distribution Network With Seawater Pumped Storage And Micro Grid

The integration of seawater pumped storage stations,renewable energies,distributed power sources,electric vehicles,elastic loads and chemical energy sources to the distribution network has posed great challenges to the reliable operation of the coastal and island distribution networks.Based on a large number of articles and field researches,this thesis focuses on the scheduling modeling of the active distribution network with seawater pumped storage stations and micro grids.Then,a dispatch optimization program for the source/grid/load of the active distribution network with seawater pumped storage stations and micro grids is proposed.By using the coordinated optimal dispatch of the adjustable power supply,load and energy storage in the active distribution network,the power characteristic curve of tie-line and the reliability of the network are improved.The main contents and achievements of this paper are shown as follows:1.The integration of seawater pumped storage stations and renewable energies to the distribution network brings some opportunities to the operation of distribution networks.On the basis of studying the mechanism and operation mode of seawater pumped storage stations,distributed generations and chemical energy storages,this thesis proposes an equivalent model of the seawater pumped storage station,and then the model of distributed generations and chemical energy storages are established.Based on the theory of economics and electricity price elasticity,the mathematical model of the elastic load is established.These models construct a foundation for building the scheduling models in subsequent chapters.2.The active distribution network contains elastic loads,interruptible loads,distributed power supplies,electric vehicles,renewable energies and energy storages.When there is no applicable scheduling method and model,the enthusiasm of each unit to participate in the dispatching will decrease,and the economic and reliable operation of the distribution network will be affected.Accordingly,a multi-time period optimal scheduling method is proposed for the active distribution network.First,an electric vehicle charging model based on elastic electricity price is built.Meanwhile,a day-ahead economic scheduling model of the active distribution network is established.Secondly,in the real-time scheduling stage,the impact of the error of renewable energy forecasts are reduced by using energy storages and electric vehicles.Based on the renewable energy forecasts and the study of the influence of the elastic electricity price on electric vehicle charging process,the optimal operation of electric vehicles,storages and flexible loads are obtained.Simulation results show that the proposed method has reduced the cost of electric vehicles charging and purchasing electricity from the distribution network,weakened the influence of the errors of renewable energy forecasts on the distribution network and optimized the characteristics of loads.3.The outstanding regulation characteristics of seawater pumped storage units are able to support the coastal and island power distribution network with the renewable energy and distributed power supply.Therefore,this thesis proposed a two-stage bi-level optimal scheduling for the active distribution network with seawater pumped storage stations and micro grids.Firstly,in the upper-level,the real-time price is determined by the equivalent load of the network.Then,according to the obtained real-time price,the economic optimal scheduling model is formulated in the lower-level.The seawater pumped storage stations,elective vehicles,interruptible loads,elastic loads,distributed generations and chemical energy storages are optimized in the lower-level scheduling model.In the real-time stage,based on the ultra-short-term prediction of loads and renewable energies,the seawater pumped storage station and chemical energy storage are used to compensate the forecast errors of loads and renewable energies.As a result,the impact of the forecast errors on the distribution network is reduced.The simulation results show that the proposed method optimizes the load characteristic curve of the tie-line of the distribution network and the charging load of electric vehicle,and reduces the impact of electric vehicles and renewable energies on the distribution network.In summary,this method achieves the source/grid/load optimal scheduling for active distribution network at multiple levels.4.Based on the above research and studying the reserve capacity that the seawater pumped storage station,chemical storage and distributed power supply can provide for the distribution network,this thesis proposes a two-stage bi-level optimization scheduling for the active distribution network including seawater pumped storage stations and micro grids.Firstly,in the upper-level,a dispatching model with the minimum fluctuation of tie-line power is established.Based on the equivalent load of active distribution network,the real-time price of the active distribution network is optimized.Then,in the lower-level,the interacted power between the seawater pumped storage station and the micro grid group is considered.Based on the real-time price,an optimal dispatching model for minimizing the operation costs of the seawater pumped storage station and micro grids is built.At the upper-level optimal scheduling model,the total power of the tie-line between the distribution network and seawater pumped storage station and micro grid is considered as a factor of the decision in the lower-level optimization model.Finally,in the real-time scheduling stage,according to the ultra-short-term forecasts of renewable energies and loads and the standby offering game model of seawater pumped storage station and micro grid group,a real-time scheduling model of multiple power sources,energy storages and main network coordination is proposed in this thesis,which can reduce the prediction errors of the renewable energy.The simulation results show that the proposed method reduces the influence of the renewable energy on distribution networks further,improves the voltage quality of the active distribution network,optimizes the load characteristics and declines the peak valley difference of tie-line in distribution networks.