Research On Stability Of Microgrid Based On Droop Control Lnverter

At present,distributed power generation technology has been widely used as countries around the world begin to focus on the development of environmentally friendly renewable energy.The micro power supply can convert the generated electric energy into AC through the inverter and incorporate it into the power grid.Therefore,the inverter is the key link of the micro grid,but it is easily affected by disturbances and loses stability.These disturbances,such as heavy load switching,short-circuit fault,input and withdrawal of some power generation devices,etc,will have a certain impact on the stability of the system,thereby endangering the stability of the microgrid.Therefore,it is particularly important to study the stability of the microgrid based on the droop control inverter.Firstly,this dissertation systematically introduces the research status of microgrid stability and several common control strategies of microgrid inverter,and analyzes the principles and characteristics of droop control of microgrids.Mathematical modeling and experimental simulation analysis are carried out for the microgrid system.Lyapunov theory and analysis methods are introduced.Then,according to the mathematical model of the droop control microgrid,a small signal model is established and linearized,and the corresponding state space matrix is obtained from the linearized model.Combining the Lyapurov criterion and the eigenvalue analysis method,the stability of the system is analyzed by using the state and distribution of the eigenvalues of the matrix.Through the trajectory change of the eigenvalues,the influence of each parameter on the stability of the small signal is studied,and each parameter is optimized.The system is simulated by MATLAB/Simulink simulation platform,and the experimental platform is built to verify the correctness of the method.A large-signal nonlinear mathematical model of the system is established and the model is reduced in order.The Lyapunov function corresponding to the large-signal model is obtained by the T-S multi-model method(Takagi-Sugeno Fuzzy Model,T-S).Using the Lyapunov stability theory,the stability of large signals is analyzed,and the stability domain of the model is obtained,and the simulation is carried out on the MATLAB/Simulink simulation platform,which proves the correctness and conservativeness of the method.The influence of parameter changes on large-signal stability is analyzed.In this dissertation,a large-signal model of a droop-controlled inverter with a DC side is designed and constructed,and the effects of DC voltage and capacitance on the large-signal stability of the system are quantified by changing the stability domain.Simulations show that nonlinear stability analysis is a feasible method to analyze the stability of microgrids during large transient events such as power generation losses or intermittent power generation,and to give system design optimization methods.