Research On Microgrid Energy Storage Capacity Optimization And Tie Line Power Fluctuation Suppressing Control Strategy

The uncertainty of intermittent energy such as wind power and photovoltaic power in microgrid increases the difficulty for external grid to dispatch microgrid.Autonomy is an internal control requirement proposed for microgrid's uncertainty characteristic to enhance the controbility of microgrid and improve the friendliness to external grid.For the problem of microgrid uncertainty,the paper proposes the microgrid uncertainty modeling and analyzing method and conducts research on microgrid energy storage capacity optimization and tie line power fluctuation suppressing control strategy while taking auntonomy as constraint.The main contents are as follows:(1)The paper proposes a microgrid uncertainty modeling and analyzing method based on emergence theory.The integration of renewable energy such as wind power and photovoltaic power increases microgrid operation uncertainty evidently,and it is difficult for the probability-distribution-based modeling method to acquire information about the microgrid operation characteristics under the influence of uncertainty factors.To solve the problem,the paper establishes the microgrid model based on emergence theory and enrich uncertainty factors' scene presentation and achieve the analysis of the microgrid operation characteristics under the influence of uncertainty factors.Finally,the examples verify the validity of the proposed modeling and analyzing method.(2)The paper proposes a microgrid energy storage capacity optimization method considering microgrid autonomy constraint.Autonomy is an internal control requirement proposed for microgrid's uncertainty characteristic to enhance the controbility of microgrid and improve the friendliness to external grid.Energy strorage plays an important role in increasing microgrid autonomy through its control for energy flow,however,the present research on microgrid energy strorage sizing mainly aims at peak shaving and price arbitrage,and the consideration for the requirement of autonomy is insufficient,so the paper proposes a microgrid energy storage capacity optimization method considering autonomy constrait.Referring to the achievements of the the information theory about entropy,the paper proposes the entropy-based modeling method for microgrid autonomy constraint.A battery energy storage capacity optimization model considering microgrid autonomy constraint is proposed.The model adds the microgrid autonomy constraint to make the microgrid have a certain ability to maintain autonomous,and considers the influence of operation state variables of battery energy storage such as state of charge and accumulated life loss.Finally,the proposed method is verified by several numerical examples.(3)The paper proposes a coordination strategy of BESS(Battery Energy Strorage System)and DLC to suppress microgrid tie line power fluctuation.The paper treats direct load control as a behavior of energy storage resource control,and proposes the DLC model based on load's energy-storage characteristic.Based on this,considering the effect of DLC,the paper optimizes the microgrid's short-term trading behavior according to two stage stochastic programming to achieve maximum economic benefit.Following the principle of increasing economic benefit and not influencing customer experience of energy consuming,the paper proposes a control scheme to suppress microgrid tie line power fluctuation entirely based on power allocation strategy which considers the operating state of load.Finally the simulation result verifies the validity of the proposed method.