Robust Model Predictive Control For Voltage Stability Of DC Microgrid With Interconnection And Coupling

In the DC-MG system,the bus voltage is an important indicator reflecting the balance of energy supply and demand in the microgrid.Due to the randomness of the output power of solar power and wind power in the DC-MG system,the sudden change of DC load,and the interconnection an d coupling caused by the input and withdrawal of distributed power generation units,the DC-MG bus voltage will fluctuate and the DC-MG will be damaged.The power balance of MG threatens the safe and stable operation of the microgrid.Therefore,studying t he voltage stability of the DC microgrid in the case of interconnection and coupling is of great significance for improving the power supply quality and safe and reli able operation of the microgrid.In view of the interconnection of multiple DGUs to form a DC microgrid system,when the load changes suddenly and the distributed power generation unit is switched on and out,the voltage stability of the DC microgrid system will be destroyed.In order to maintain the stability of the DC bus voltage,this paper firstly writes the state equations for the DC microgrid system composed of two DGUs interconnected and coupled,and establishes the pseudo-steady state mathematical model of the DC microgrid system.Then the distributed robust model predictive control strategy is introduced into the DC microgrid,and the corresponding local controller is designed for each distributed power generation unit according to this control strategy,and the voltage fluctuations appearing in the microgrid under interconnection coupling are predicted It also analyzes the stability of the distributed robust model predictive control system of the DC microgrid in the case of interconnection and coupling,derives the establishment of convex optimization problems and solves the feedback gai n,so that the DC microgrid system can meet the plug-and-play of distributed power generation units.Use operation.When the DGU is switched on or out of the DC microgrid system,the DGU connected to it at most needs to update its corresponding controller,and other controllers can ensure the stability of the system without any action.In addition,the design of the controller only needs to DGU and the parameters of the transmission line connected to it.Finally,the designed partial controller was simulate d and checked in Matlab,and the simulation results verified the effectiveness of the control method.For a DC microgrid system composed of multiple distributed power generation units interconnected and coupled,sudden load changes and DGUs input or withdrawal will cause voltage fluctuations in the microgrid system.Based on the robust one-step set,the thesis studies the Tube-RMPC method of DC microgrid in the case of interconnection and coupling.Firstly,the offline design is based on the polyhedral invariant set,and the extended terminal constraint set of the polyhedral invariant set sequence is obtained.Then,on the basis of extending the terminal constraint set,the Tube-RMPC strategy based on the robust step set is introduced into the DC microgrid,and the model predictive controller based on the robust step set is designed.This method not only expands the initial state allowable area of the robust model predictive control,but also improves the robustness of the DC microgrid system.Then the stability of the robust model predictive control system of the DC microgrid is analyzed under the condition of interconnection and coupling.When the load changes suddenly and the DGUs are switched on or out,the DC microgrid system under the condition of interconnection and coupling will converge to the minimum robust positive invariant set centered on the origin,ensuring the stability of the bus voltage of the system.Finally,the simulation verifies that the control strategy has a better control effect on the interference system.