Research On Distributed Coordinated And Switching Control In Microgrid

With the rapid development of economy and the increasing of population,the demand of electric power is growing,and the reliability and quality of power supply are getting higher.But the traditional centralized power generation has many problems,such as the long transmission distance,high operating costs,difficult maintenance,and environmental pollution seriously and other issues,it is difficult to adapt to the needs of users of electricity.Facing the current situation and challenges,the development of microgrid construction is an effective method to solve the problems of energy and environment in our country.Grid-connected operating mode and islanding operating mode are included in microgrid.The stability of the distributed power supply voltage in islanding operating mode and during the microgrid mode switching are the key and difficult problems in the research of microgrid.The two problems of microgrid are studied in this paper,and an effective control scheme is designed to ensure the stable operation of microgrid.Firstly,the distributed coordinated control based on multi-agent system is proposed to improve the voltage of micro-grid.In lower-level agent,the decentralized control is designed as double-loop controllers through the inverter of each distributed energy resource,including an outer-loop power controller based on droop control and inner-loop voltage and current controller based on the fractional order PID.In upper-level agent,the distributed coordinated control is designed to make voltage consensus and proportional power sharing of all distributed energy resources.Secondly,in order to deal with the voltage and frequency mutation caused by the switching mode of the grid connected to the islanding operation mode,a microgrid operation mode smooth switching control strategy based on equal-time interval switching is proposed.The concept of switching system is introduced,and the switching controller is designed.Switching controller according to the voltage measurement device determines the operation mode of the microgrid and the control strategy of the master unit,and ensures that the micro grid can be smoothly switched from the grid mode to the islanding mode.The master unit is controlled by PQ control in the grid connected operation mode,the V/f control is adopted in the islanding operation mode,and the other distributed power supply is controlled by PQ control.Finally,the correctness and validity of the control strategy are verified by MATLAB.