Research On Independent Microgrid Parallel Inverter Based On Drop Control Strategy

With the rapid development of the world economy,global environmental problems and energy shortages have become an important issue in the process of world history.Developing environmentally friendly renewable energy microgrid has become the first way to solve the energy crisis and environmental pollution in the world.In recent years,with the increasing installed capacity of renewable energy such as photovoltaic and wind power,distributed generation technology has been widely used.As a kind of distributed access power,microgrid can give full play to the advantages of distributed generation technology and reduce its impact on the power grid.As a typical example of integrated distributed generation,microgrid can realize grid-connected operation and independent operation by integrating advanced power electronics technology,control technology and communication technology,which improves the reliability and flexibility of power supply to a certain extent.Inverter is the core unit of microgrid,and its operation stability has a significant impact on the output characteristics of microgrid.However,too many inverters in the micro-grid will make the inertia of the micro-grid system smaller,and it is very vulnerable to instability.Therefore,in isolated cases,whether the micro-grid system can maintain small disturbance stability is one of the important criteria to judge whether the independent micro-grid system has stability.Therefore,in this paper,the droop control strategy of the inverters in the independent microgrid system is taken as the research object.It is of great significance to study the operation control and stability mechanism of the independent microgrid system for promoting the development of distributed generation technology.The main work and conclusions of this paper are as follows:(1)Summarize the development status of microgrid at home and abroad,introduce the control method of microgrid system and the control strategy of microgrid converter systematically,and model and simulate the independent microgrid system on the basis of droop control strategy.(2)According to the mathematical model of droop control strategy of independent microgrid system,the small signal model of independent microgrid system is established.Based on eigenvalue analysis method and Lyapunov criterion,the small signal stability of independent microgrid system is analyzed,and the approximate range of control parameters to maintain stable operation of the system is obtained and preliminarily optimized.The stability of the system is judged by comparing the eigenvalues before optimization and the eigenvalues before optimization.Based on the simulation platform of MATLAB/Simulink,the simulation analysis before and after optimization of the control parameters of the independent microgrid system is carried out to verify the validity of the small interference analysis results.(3)The main circuit,control circuit,system software and hardware circuit of the independent microgrid system are designed in the laboratory,and the experimental verification before and after the optimization of the control parameters of the independent microgrid system is carried out.The validity of the theoretical analysis and simulation results is verified from the experimental aspect.