Research On Micro-grid Capacity Allocation Based On Mixed Integer Second-order Cone Programming

In recent years,the sharp increase in energy demand and the contradiction between fossil fuel exhaustion have become more and more prominent.The effective use of clean energy such as wind energy and solar energy has gradually appeared in people's field of vision.The development of distributed generation technology and micro-grid technology has provided an effective way to make good use of large-scale distributed energy.However,large-scale distributed generation access to the micro-grid system will negatively impact the system's active network loss,power flow,harmonics,short-circuit current,dynamic stability,and transient stability.The blind introduction of distributed power supplies may result in System stability,reliability and deterioration of power quality.As the effective use of clean energy and given a large number of important means of distributed energy,reasonable planning for micro grids in the location and capacity of distributed power supply is the most important part of optimized configuration of micro-grids,and is the first job of micro power grid planning and construction.On the basis of clarifying the purpose and significance of the optimal configuration of micro-grid capacity,in order to reduce the negative impact of distributed power access on micro-grid,and improve the system operation economy and reliability.In this paper,the optimal configuration of the capacity of micro-grid with distributed generation is studied systematically from two aspects: the optimization model and the optimization algorithm.Considering that if the distributed power generation unit is directly used as a PQ node or a PV node to access the microgrid system,it cannot reflect the random volatility characteristics of distributed power generation.This paper analyzes the distributed generation from the working principles and characteristics in-depth.Focus on the randomness of wind power generation and photovoltaic power generation,a discrete power state model of wind power generation and photovoltaic power generation is established to describe the randomness of the distributed power supply.Based on this,this paper set up the optimal allocation model of micro grid capacity,which to minimize the loss of network loss,and take the randomness of distributed power supply,the power flow constraint,the voltage limit constraint and access capacity constraint into account.Combining the characteristics of non-convex nonlinearity of constraints in the optimization model of this paper.The second-order cone programming is used to relax the original problem,so that the original problem can be solved effectively by using the second-order cone programming method.A condition that only depends on the network structure to verify the global optimality of the solution is proposed.MATLAB/CPLEX toolbox is used to simulate the 30-node system.The results show that the proposed method has good convergence and can be used to judge whether the original model can be solved by the relaxation model without solving the model.At last,taking a micro-grid system as an example,the optimal configuration scheme without considering the randomness of distributed power supply and considering the randomness of distributed power supply is obtained.The simulation results show that considering the randomness of distributed power generation can allocate the access capacity effectively.This configuration scheme can effectively reduce network losses and enhance the economy and reliability of micro-grid operation.