Analysis Of Frequency Stability Of Microgrid Based On Droop Control

Micro Grid could increase the efficiency of using renewable energy as a effective way to access the distributed generations.Compared with the traditional grid,the capacity of microgrid is relatively small,the power output and the variation of the load occupy a large proportion of the capacity of microgrid, so the system will be more easily affected by disturbance when the island operation is going on,thus disturbing the stable operation of microgrid.Compared with traditional rotary generators,inverter-interfaced distributed generations and control strategy which are largely used in microgrid have different operation characteristics.The traditional method of stability analysis have some deficiencies in researching on Micro Grid.First,this paper introduce the control strategy of Micro Grid and make a comparing and describing of variable control methods.The control theory of the distributed generations is analyzed.This paper also sums up the theory of power system stability and introduces the latest development of the frequency stability.Then a linear analysis and improvement of droop controller of the distributed generations are maded which enhance the stability and accuracy of the controller.Second,this paper,taking varied circumstances which have mentioned above into consideration,has estabilished the small-signal modeling of microgrid based on droop control,analyzed the frequency and damping characteristics near the operation point. Us ing the model constructed,the eigenvaluse are calculated at different steady state operation points.The frequency stability are analyzed when the line impedance and the droop gains change. While at the same time,using MATLAB/SIMULINK software to do time domain simulation of the model of microgrid,verifying the function of the LCL filter in increasing stability of microgrid when distributed generations are parallelled in short distance.Finally,this paper researches the dynamic stability of Micro Grid System.Experimental results show that the sag parameters greatest impact on the stability of Micro Grid.Large sag parameters will reduce the system’s damping parameters.With sag parameters increasing,The status of Micro Grid system is moving from frequency stability to low frequency oscillation,and instability.