Research On Optimal Configuration And Economic Operation Of DC Micro-grid

With the booming development of economy,the contradiction between the growing demand of global energy and the exhaustion of traditional fossil resources is becoming more and more serious,and the over exploitation and use of fossil fuels has made the ecological environment deteriorated rapidly.Power system is facing many challenges,and all sectors of society advocate use renewable clean energy and build new smart grid,and distributed generation and micro-grid technologies are gaining more and more widespread use.Currently,the major research about micro-grid focuses on AC micro-grid.However,many advantages of DC micro-grid are prominent after that the DC transmission technology has developed rapidly and DC loads have increased extensively.The network optimal of micro-grid is the key problem to be solved in the planning stage,which affects operating performance of system directly.In this paper,the issue of optimal configuration and economic operation of DC micro-grid is studied in depth.The main contents are as follows:First of all,the structure characteristics and applicable conditions of ring-typed,radiation-type,and feeder-type of DC micro-grid are briefly analyzed,and the radiation-type structure is selected as the object of research.And the working principle and mathematical model of each unit of DC micro-grid,for instance,photovoltaic cells,wind turbines,batteries,and power electronic converters,are studied.And then,the influence mechanism of node voltage and line loss after that distributed generators are connected to the DC micro-grid is studied.Aiming at the change of power flow,this paper proposes loss sensitivity factor and voltage sensitivity factor to optimize the access position.By using MATLAB simulation software,the static mathematical model of capacity optimization is established,and the objective function is to minimize the sum of power loss and total voltage deviation in the DC micro-grid.The liner decreasing weight particle swarm optimization(LinWPSO)is used to verify the example.Moreover,the economic cost optimization problem of DC micro-grid with operating performance is studied.The dynamic mathematical model of the economic cost optimization consider the output fluctuation of photovoltaic cells and wind turbines,and the objective function is to minimize the economic cost with combining the grid inverter and real-time price of electricity.This paper proposes the solar-wind complementary property and the reliability of power supply and the environmental protection as operating performance of system to participate in optimization.The influence of different operating performance on the configuration scheme is obtained by some simulation.Last but not least,based on the optimal configuration of the DC micro-grid,the minimum power supply cost and loss probability of the system is used as the objective function which combines with the time-of-use price factor of the public power grid,to establish a daily economic dispatch model.Taking the typical daily climate data and load data as an example,the output of each unit of the DC micro-grid under both islanding mode and grid-connected mode is analyzed,and the load power supply cost and loss power supply probability of the two operating modes are compared.