Research On Dynamic Control Strategy Of Cascade Energy Router Based On DAB

With the global energy shortage,environmental pollution and other issues,the energy Internet has gradually become a research hotspot in universities and research institutes at home and abroad.Energy router is the core component of the energy Internet,which directly determines the energy scheduling,voltage level transformation and other core functions of the energy Internet.Cascaded energy router topology has the characteristics of small volume and weight,flexible control and high power quality,which is an important part of future power development.Aiming at the complex application scenarios of cascaded energy router topology,the output voltage of rectifier stage is unbalanced,and the output stage has higher requirements for dynamic performance,the control strategy is studied.Specifically,firstly the structural characteristics of the energy router are summarized and selected from a macro perspective,focusing on the classification and introduction of the core component of the energy router-isolated bidirectional DC/DC converter.The dual active full bridge DC/DC converter which is the most matching with the energy router is selected as the isolation stage,and finally the cascade energy router circuit topology which is the most matching with the energy Internet attribute is determined as the research object of this paper.Subsequently,the topological equivalence of cascaded energy routers is analyzed,and the hierarchical control idea is used to control the rectifier level and isolation level of cascaded energy routers respectively so as to facilitate topological equivalence.In order to control the output voltage balance of the cascaded H-bridge in the rectifier stage and make the cascaded energy router equivalent to the independent input parallel output topology,the control strategy of the isolation stage is designed in this paper.The rectifier stage is modeled and analyzed.On this basis,a voltage and current double closed-loop control strategy with output current feedforward is proposed,and its feasibility is verified by experiments.Then,the working principle,working mode,power transmission characteristics and other electrical parameter models of three different phase shift control of DAB converter are analyzed.At the same time,it is concluded that the traditional single phase shift has serious power backflow phenomenon and small control range,and then the extended phase shift and double phase shift control based on single phase shift control are proposed and simulated.The experimental results are consistent with the analysis,which greatly improves the power backflow phenomenon and greatly expands the control range and improves the control flexibility.Finally,in order to facilitate the following experiments and the formulation of control strategies,the parameters of the main devices of the isolation stage are designed,and the small signal modeling and transfer function derivation and analysis of the DAB converter are carried out.The traditional voltage closed-loop design of the system is used as the basis of the traditional voltage closed-loop control design of the independent input parallel output equivalent topology.The analysis shows that its dynamic performance improvement of the DAB is limited.In order to further improve the dynamic performance of the output of the cascade energy router when the load condition of the output is abrupt and the input voltage is abrupt,and then aiming at the independent input parallel output equivalent topology of the cascade energy router,based on the single phase shift control and the direct power control idea in the field of motor control,the load current feedforward is introduced,and the voltage closed-loop control and power balance control are combined.A composite control strategy is proposed and compared with the traditional closed-loop control.