Study On Control Technology For Multi-Microgrids System With Electric Vehicles

The more and more extensive application of new energy is presented in the power system,especially in the microgrid.The participation of distributed generation and electric vehicles(EVs)brings randomness and uncertainties to the operation of microgrid.Therefore,the study of the control technology for microgrid system is of great significance.The anti-interference ability of islanded microgrid is weak.In this paper,a multi-microgrids system with several microgrids interconnected is built to improve the stability of microgrid.In this paper,on the basis of robust model predictive control technology and virtual synchronous generator control method,the integrated control method of multi-microgrids system is studied.The specific research work is as follow:(1)The construction of microgrid model is the basis of integrated control technology research.It is worthy of attention to select the appropriate control method and establish a proper model.Firstly,several inverter control technologies are introduced in this paper.Combined with control theory and the operation characteristics of different equipment,the modeling methods of EV charging station,photovoltaic power generation system,wind power generation system,gas turbine and controllable load are studied,and their operation characteristics are analyzed.Finally,a multi-microgrids system is built with each equipment,and the corresponding simulation is carried out to analyze the operation characteristics of the multi-microgrids system.(2)When the microgrid is in the island operation state,the frequency stability is easily affected by the disturbances such as photovoltaic power generation,wind power generation and load.The regulation capacity of the microgrid is limited,which brings difficulties to the frequency regulation of the island microgrid.In this paper,the equivalent frequency control model is studied according to the structural characteristics of each equipment.Micro gas turbine,EVs and controllable load are added to the frequency regulation of microgrid.The randomness of EV users’ behavior is considered.Based on this,a frequency control model of multi-microgrids is built.Based on the robust model predictive control(RMPC)theory,a new frequency controller based on LQR-RMPC is designed in this paper by adding a linear quadratic regulator(LQR).The LQR-RMPC frequency controller improves the control performance of the whole system.The frequency oscillation is effectively suppressed.And the stability is enhanced in multi-microgrids system.Finally,compared with other control methods,the superiority of the proposed control method is demonstrated through the simulation in different cases.(3)In the operation of microgrid,the ability of the traditional inverter control method to maintain voltage and frequency stability is limited,especially for the islanding microgrid which lacks the support of the main grid.Based on the robust model predictive controller,an improved voltage frequency integrated control method on the basis of VSG is proposed in this paper.The output from the virtual governor module according to the control signal from the improved robust model predictive controller is modified through this method.It is applied to the control module for the EV dynamic simulation of the actual power system,so that the frequency and voltage can restore stability quickly under disturbance.And the robustness and stability of the microgrid system are improved.Finally,the effectiveness of the method is verified through simulation.In the last part of the paper,the summary and the future work are presented.