Research On Stability And Control Strategy Of DC Micro Grid

As a new type of energy,renewable power is playing an increasingly important role,but its obvious flaws are always difficult to solve.With the development of power electronics technology,DC microgrid,which can carry distributed power sources,has been highly valued.Compared with AC power supply form,DC microgrid has more advantages in equipment input,power loss,operation difficulty,development prospects.This paper focuses on the stability and control strategy of DC microgrid.After establishing the state space model of the important elements of the DC microgr id,the small signal stability model of the single bus system is derived.According to the control parameters of this system,this paper analyzes the influence of system control parameters on the stability of small disturbance by using eigenvalue analysis method.Then the model of pure resistance and resistance transmission line is established,which improves the small interference model of the DC microgrid.The influence of the topology change,that is,the electrical distance on the small signal stability is analyzed successfully.According to the functional characteristics of each unit of DC microgrid,this paper establishes their respective control models,and the models are built on the MATLAB/Simulink platform for verification.Among them,the photovoltaic unit adopts the MPPT control based on the disturbance observation method,the battery unit adopts the improved droop control method,and the grid-connected converter and the bottom busbar adopt the dq decoupling control and the constant voltage control method respectively.On this basis,this paper builts the radiant stratified bus DC microgrid with various units and designs the coordination control strategy of the whole system.The simulation proves that the system can operate reliably in grid-connected mode and island mode.Based on the established DC microgrid,in order to improve the response performance of the system to the disturbances,this paper simulates several common dynamic processes,including grid-connected AC side short circuit,grid-connected DC side short circuit,island load mutation and unplanned island effect.By changing the parameters of the system,this paper explores the influence law of each parameter on the disturbance process,and proposes the improvement methods and suggestions of DC microgrid for different disturbances according to the observed law.