Coordinated Control Strategy Of DC Microgrid Based On MMC Power Electronic Transforme

Microgrid integrates distributed energy,storage and load,which is considered as an effective way to solve the problem of high permeability of distributed energy.Compared with AC microgrid,DC microgrid eliminates the conversion process.Meanwhile,DC microgrid has the characteristics of simple structure,good controllability and high power quality.As the core of energy interface and management of microgrid,power electronic transformer has received extensive attention and research.Based on this,the optimization control strategy of MMC power electronic transformer and power coordination control of DC microgrid are studied in this paper.Specific research contents are as follows:Firstly,the research background and significance of the subject are introduced,and the current research status of power electronic transformer and DC microgrid power coordination control is discussed.Secondly,the mathematical model of MMC converter is studied Then,the working principle and mathematical model of DAB converter are analyzed in detail.Aiming at the problems such as large current stress and the dynamic response capability to be improved under the traditional control strategy,a comprehensive optimal control strategy considering current stress optimization and output voltage model predictive control is proposed.At the same time,the overall control of ISOP-DAB converter is improved based on the comprehensive optimal control strategy of single-module DAB converter and the input side voltage equalization is considered.The simulation models of single-module DAB and ISOP-DAB converter are established.The simulation results show that the comprehensive optimization control strategy can greatly reduce the current stress of DAB converter and improve its dynamic response capability under the condition of input voltage and load mutation,which verifies the correctness and effectiveness of the proposed optimization control strategy.Finally,the DC microgrid control strategy based on DC bus voltage signal is adopted,and the bus voltage is divided into three sections to make DAB converter work separately.As the control bus voltage,energy storage is added for power compensation and grid-connected through MMC converter and ISOP-DAB converter,the DC bus voltage of microgrid is kept stable and there is no surplus power in the system.