Research On Small Disturbance Stability Of Microgrid

Microgrid,also known as distributed energy island system,as an important technology of the future energy chain,efficiently integrates various types of distributed power sources.Microgrid has many advantages,such as energy clean,flexible regulation,compatible environment and low line loss.It has a far-reaching impact on the construction of global power grid.As the penetration rate of distributed power sources continues to increase,the scale of the system becomes larger and more complex.the small disturbance events in the microgrid operation show strong randomness and uncertainty,which brings serious challenges to the operational stability of the microgrid.Studying the stability mechanism of microgrid under small disturbance is not only the basic task of ensuring the reliable operation of microgrid,but also the inevitable demand for giving full play to the advantages of microgrid.Therefore,the work of this thesis focuses on the study of the small disturbance stability of microgrids.The main research work is as follows:First,considering the characteristics of multiple micro-source forms and multiple control modes coexisting in micro-grid,this thesis studies the composition and working principle of typical distributed power sources such as photovoltaic system,wind system and energy storage system in micro-grid,A complete mathematical model describing the dynamic behavior of each subsystem is established.Based on Matlab/Simulink simulation software,the micro-source model construction and simulation analysis are carried out to study the effects of environmental disturbances such as illumination changes and wind speed changes on the operating characteristics and output characteristics of each micro-source.Secondly,based on the mathematical model of microgrid,the small disturbance stability analysis model of the system is studied.In this thesis,the detailed and quantitative mathematical derivation and analysis of the distributed power state space in the microgrid are carried out,The general characteristics of the state space after micro-disturbance of microgrid are studied from the perspective of mathematical model.based on the eigenvalue analysis method,the typical distribution of the eigenvalues of the microgrid is analyzed by Matlab simulation,and the characteristic root stability analysis is carried out on the key parameters affecting the operating characteristics of the microgrid.Through parameter changes,tracking the trajectory of the characteristic root of the system coefficient matrix,studying the cause mechanism of the system root distribution,and obtaining the general law of the system stability change with the parameter.Thirdly,an innovative research on the small disturbance stability research method is proposed.A small disturbance stability evaluation technique based on the “fuzzy-cloud” model is proposed.On the basis of the previous research,the key influence parameters are selected to construct the micro-grid small disturbance stability evaluation system.The interaction matrix design method is used to describe the possible coupling relationship between the evaluation indicators,and the influence degree of the evaluation index on the system stability is reasonably determined.To the problem of ambiguity and randomness of data and indicators in the evaluation process,the cloud model is applied to obtain the stability level of each indicator,further improving the accuracy of the evaluation system and realizing the stability determination of the microgrid.It provides a new way of thinking and solution for the identification of the operating state of the microgrid.