Static Voltage Stability Analysis Of Islanded Microgrid Based On Holomorphic Embedding Method

Micro-grid technology can effectively integrate the advantages of distributed generation,and also provide a new technology scheme for the large-scale application of new energy and renewable energy grid connected generation.At the same time,as an effective complementary form of traditional large grid,it can improve the reliability of power supply and power quality.The operation mode of micro-grid is divided into grid connected and island connected.The control mode of islanded micro-grid mainly includes master-slave control and peer-to-peer control.The operation mechanism of master-slave control islanded micro-grid is similar to that of traditional large grid,and peer-to-peer control islanded micro-grid is also called droop control islanded micro-grid,but its structure and operation mechanism are unique compared with traditional grid.The voltage stability of power system is of great significance to its planning and operation,so it is necessary to carry out the static voltage stability analysis and research of the droop control islanded micro-grid.Power flow model and power flow algorithm are the basis of static voltage stability analysis,and the convergence of power flow calculation is always a challenging problem.The holomorphic embedding method(HEM)can ensure that the system solution converges when it exists,and the system oscillates when there is no solution,meanwhile the signal without solution is given.Therefore,this paper studies the application of HEM to the steady-state analysis and static voltage stability analysis of islanded micro-grid system.In this paper,firstly,the mathematical theory of HEM is introduced,and based on the master-slave control islanded micro-grid system,the basic principles of traditional HEM and an improved HEM are explained.The application of HEM on IEEE33 node master-slave control islanded micro-grid system is analyzed.Then,based on the basic principles and ideas of the two algorithms,this paper proposes a holomorphic embedding power flow calculation model for the droop control islanded micro-grid system to solve the problem of the uncertainty of the power flow steady-state solution of the Newton Raphson method(NR).Aiming at the accuracy problem of HEM,this paper adopts the method of combining HEM with NR to ensure the accuracy of power flow calculation solution.Taking IEEE16 nodes and IEEE33 nodes droop control islanded micro-grid system as examples,the superiority of HEM in convergence is verified by comparing HEM with NR on calculating the steady-state solution of the system.Furthermore,by comparing continuous power flow(CPF)method and HEM to get PV curve,the correctness of HEM in the static voltage stability analysis of droop control islanded micro-grid is verified.Finally,based on the algorithm proposed in this paper,the influence of droop parameters on the static voltage stability of the system is analyzed.