Power Flow Control And Optimization Of AC Microgrid

Distributed generation has strong flexibility,which can alleviate the increasingly serious power transmission pressure of large-scale power grid.It is one of the effective ways to efficiently utilize renewable energy sources and reduce environmental pollution.In order to give full play to the comprehensive benefits of distributed generation,researchers and scholars all over the world have put forward the concept of microgrid.As the initial form of smart grid in the future,microgrid has become a hot spot in the research of various countries because of the convenience and high autonomy of renewable energy.The power flow control and optimization of microgrid is important to improve the utilization of new energy consumption,and improve the stability of power system.In this paper,the method of power flow control and optimization among distributed microgrid,micro grid and large power grid and multiple microgrid within the same power system is deeply studied.Firstly,the modeling and control of distributed generation in AC microgrid are studied in this paper.This paper introduces the composition and structure of microgrid,and the mathematical model,grid connection strategy and control method of various distributed power sources.At the same time,this paper further studies the operation of micro grid control strategy,based on the concept of hierarchical control,according to the control objectives and control time scales,the AC microgrid power flow control and energy management is divided into three levels of control.The primary control is distributed power and load local autonomous control,and the two level control is the bias compensation control of microgrid voltage and frequency,and the three level control is the upper layer energy optimization and scheduling of microgrid.Secondly,this paper studies the power flow planning and distribution method of single microgrid from the aspect of optimal scheduling.The multi time scale micro grid multi-objective optimization model based on the day before scheduling by improved NSGA-II algorithm is used to solve the multi-objective optimization model of micro grid.In the days of real-time optimization,according to the use of ultra short term prediction on the day before step by step optimization scheduling scheme for rolling amendment.Finally,an example is given to verify the effectiveness of the proposed microgrid optimization model.Finally,a multi microgrid optimal scheduling model based on target cascade method is proposed for the large scale active distribution network with multi microgrid.By decoupling the transmission power of tie line,the parallel and independent solution of the distribution network and Microgrid optimization model is realized.The simulation results of an improved IEEE30 node system show that the proposed method can obtain the global optimal solution accurately and has good convergence characteristics.Compared with the centralized solving method,with the number of micro grid distribution network expansion,the solution method has better efficiency,provides an effective research method for large-scale multi microgrid system flow optimization.