Research On Control Method Of Flexible Interconnected Converter Of Hybrid Microgrid

With the increasingly serious problems such as energy crisis and environmental pollution,clean and renewable energy has attracted more and more attention.Hybrid microgrids have the advantages of both AC microgrids and DC microgrids,which can better accept various distributed generations and loads,improve the flexibility of distributed power consumption,and improve the utilization efficiency of new energy,which has become a hot topic in current research.As an important link connecting the microgrids on both sides,flexible interconnected converter plays an important role in coordinating the power balance between hybrid microgrids and the stable operation of the system.Therefore,the research on the control strategy of flexible AC/DC interconnected converter has great practical significance and application value.Firstly,this paper analyzes the working principle of the flexible AC/DC interconnected converter with non-isolated topology,and establishes its dynamic mathematical model based on ABC coordinate system and d-q coordinate system.Secondly,the droop control characteristics of frequency active power,voltage reactive power and voltage active power in hybrid microgrid are described respectively.By explaining the idea of uniting droop characteristics,the droop coordinated control method is proposed.Through the analysis and design of feedforward decoupling control,the droop feedforward decoupling control method of flexible AC/DC interconnected converter is proposed,and the control system is designed to realize the power balance of hybrid microgrids.Then,aiming at the problem of poor stability control of droop control,PI control is selected to replace droop control.Through the judgment idea of subnet bus voltage value,a voltage reference control method is proposed,that is,after the unity treatment of AC bus voltage and DC bus voltage,the current reference value sent into current loop control is obtained through active and reactive links.Aiming at the problems of feedforward decoupling control,a new current loop control method based on internal model decoupling control is proposed.The control system is designed in detail through mathematical theory.Internal model decoupling control effectively reduces the number of parameters set by the controller,greatly reduces the complexity of the controller,and makes the system have ideal dynamic response characteristics and robustness.Therefore,a voltage reference internal model decoupling control method for flexible AC/DC interconnected converter is proposed to maintain power balance and obtain ideal dynamic response characteristics.Finally,according to the corresponding indicators and constraints,the parameters of DC side capacitance and LC filter circuit of flexible AC/DC interconnected converter are designed,and the overall simulation model of hybrid microgrid is built in Matlab/Simulink.Through the comparison of simulation results,the superiority of voltage reference internal model decoupling control of flexible AC/DC interconnected converter is proved,and the effectiveness of the control method is further verified in the simulation results of different working conditions.