Research On Large-Signal Stability Analysis And Active Damping Methods Of DC Microgrid

As the rapid development of society,people's demand of electricity is increasing day by day.But at the same time,the traditional fossil energy is increasingly scarce,therefore it becomes more and more urgent to find alternative energy sources.Distributed energy sources,such as solar and wind power have received wide attention due to their advantages of cleanliness and inexhaustible.Compared with the direct connection of distributed energy sources to large power grid,the utilization of distributed energy sources can be improved through the stability and control strategy of microgrid.As one of the main ways in microgrid,the DC microgrid does not need to consider frequency,reactive power,phase angle and other issues,which makes the DC microgrid become the main way to connect distributed energy sources to the large grid.Therefore,it has practical significance for the research of the stability of DC microgrid.There are a large number of power electronic converter loads in DC microgrid.The constant power characteristics is shown when these loads are controlled through closed loop control,which will reduce even destroy the stability of DC microgrid.The stable operation of DC microgrid is a prerequisite to ensure reliable power supply to users.At present,the research on stability of DC microgrid mainly focuses on small-signal stability.However,the instability of DC microgrid caused by large disturbances such as sudden load switching or sudden changes in load can not be ignored.In this paper,the large-signal stability of DC microgrid with multiple constant power loads is studied.Firstly,the large-signal mathematical model of DC microgrid is built.Secondly,the Lyapunov eigenvalue method is used to establish the Jacobi matrix and draw out the trend graph of characteristic root changing with constant power load,so as to estimate the power limit value to ensure the safe operating power range of constant power load.finally,the fuzzy model corresponding to DC microgrid is established by using T-S fuzzy model method.The energy function is determined by multiple linear inequalities corresponding to fuzzy model.The influence of initial operating state of DC microgrid on the stability is analyzed.In order to reduce even eliminate the impact of large disturbances,it is necessary to improve the stability of DC microgrid.In this paper,various active damping compensation methods are used to improve the stability of DC microgrid.Large-signal modeling of DC microgrid with various active damping compensation methods is carried out,and the effects of various active damping compensation methods on power limit and region of asymptotic stability are compared and analyzed respectively.Finally,the correctness of theoretical analysis is verified through the establishment of Matlab/Simulink simulation and experiments based on RTLAB hardware in the loop.