The Stability Analysis Of Microgrid Based On Impedance Modeling And Analysis

With the gradual development of renewable energy,micro-grid has become a trend for the rational use of renewable energy.However,because the micro-grid is a power system based on power electronic converters,from the perspective of grid stability,there is a big difference between the stability analysis of the traditional power grid and the stability analysis of micro-grid.Until now,the theory of system modeling and stability analysis of micro-grid still need more improvement,which has brought challenges to the large-scale popularization of micro-grid.Based on the theory of impedance analysis and the modeling of a converter,the impedance modeling method is applied to a series of micro-grid topological structures.First,impedance modeling of inverter viewing from DC side is presented,and the effectiveness of impedance viewing from DC-side is verified by simulation and experiment.The results show that DC-side output impedance has an obvious influence on the stability of the system.Second,impedance analysis of the inverter with different control strategies shows that the controller design and controller parameters have some influence on the DC-side impedance expression,which further reflects the stability margin of the DC-side bus voltage.Then,Impedance modeling of cascade system is carried out,the analysis and simulation verify the correctness of impedance criterion of cascade system.Finally,a DC micro-grid system including converter control is established,and the impedance criterion of multi-machine system is introduced.The instability of multi-machine system is caused by the change of line impedance,verifying the correctness of impedance analysis.The influence of line impedance inductor on multi parallel converter is also verified.