Research On Coordinated Operation Control Strategy Of AC/DC Hybrid Microgrid

The environmental pollution,energy crisis and other issues caused by traditional fossil fuels,Which makes people draw attention to the development of renewable energy.Microgrid is a efficient way to integrate distributed renewable energy into traditional electric power application.AC/DC hybrid microgrid combines the advantages of the AC microgrid and DC microgrid.which is one of the popular research field in microgrid.This paper selected the AC/DC hybrid microgrid as the research subject and explored the system coordinate operation control strategies.The analysis and design methods from up to down,global to details,and with comprehensive coordination are used in this paper.The main work is as follows:(1)Focus on the insufficient designs of independent DC microgrid and AC microgrid structure,a novel AC/DC hybrid microgrid structure is proposed in this paper.It analyses composition content of the AC/DC hybrid microgrid structure in detail,establish the mathematical model of the AC/DC hybrid microgrid,and analyses design principle of the control methods for distributed generation microsource.The works constitutes the basic framework for the thesis research.(2)For the islanding detection problem in AC/DC hybrid microgrid,a novel island detection control strategy for the converter with active islanding detection was presented in this paper,which realized the fast smooth switch from the grid-connected mode of the converter fast smooth switch to the islanded mode without Non-detection Zone.The simulation and experimental results show the effectiveness of the proposed control method.(3)Aim at the problem of AC/DC interface converter in operation mode,this paper proposes a novel mode transfer control strategy,contains the compensation algorithm for the transient from grid-connected to stand-alone mode transient process,and the pre-synchronization method for the stand-alone to grid-connected mode transient process.The proposed control method realized the seamless mode transfer,the output voltage and current of converter are smooth without impact during the switching of operating modes.The simulation and experimental results verify the validity and reliability of proposed methods.(4)Based on the previous studies,a fully decentralized control operation strategy on DC bus voltage level was proposed.The designs the system operation mode,the work mode switching mechanism and switching conditions.The proposed strategy can use renewable energy efficiently,improve the reliability of the power supply for the critical loads,and operation stably both steady and transient condition.The simulation and experimental results show to verify the effectiveness and feasibility of the proposed control operation strategy.(5)To extend the research about the possible failures of AC/DC hybrid microgrid,This paper developed a VSG(Voltage Sag Generator)in transformer form based on LabVIEW.The VSG controlled by a safe and reliable operation of PC monitor.Accurately set the duration of the voltage sag,simulate various types of voltage sag faults.The AC/DC hybrid microgrid system which is proposed in this paper coordination operating properly.Renewable energy generation is fully used,the design system keep stable during work mode switching.Converter output voltage and current waveforms are smoothness,which protect the important load sustained and stable power supply.The control strategy of each part in the system are tested,validated by experimental platform and meeted the requirements.