Research On Control Method Of Three-port DC-DC Converter

As society pays more and more attention to environmental and energy issues,traditional energy can no longer meet the needs of current power generation technologies.Solar energy and wind energy have become the core energy sources in the energy Internet.The energy produced by solar cells fluctuates greatly due to changes in light intensity and temperature over time.Therefore,it is essential to supplement an energy storage equipment to the system to regulate the equilibrium of energy furnish and requirement in the system to fulfill the electricity requirement and electricity quality of the load.Three-Port Converter(TPC)has the characteristics of being able to achieve electrical isolation and high power density,and can connect photovoltaic cells,energy storage devices and loads.Therefore,three-port converters are used in photovoltaic power generation systems.As the research focus of the subject.This thesis first presents the fundamental,modulation mode and energy delivery situation of the two-port converter(DAB),and then derives the basic working principle and power transmission equation of the isolated three-port DC-DC converter on the basis of the DAB converter.Secondly,the control strategy of the DAB converter is studied to prepare for the study of the control strategy of the isolated three-port DC-DC converter.Based on the phase-shift modulation strategy,Two control methods are used to control the DAB converter,and simulation software is used to control the system.Simulation is utilized to confirm the accurateness of the control means applied.Under the application background of photovoltaic power generation,the control method of isolated three-port DC-DC converter has been studied in depth.The maximum power point tracking method is applied for the PV port to make the photovoltaic panels always work at the correct working point.For coupling problems,feedforward decoupling is used to simplify the relationship between model variables.In addition,in view of the parallel resonance phenomenon caused by the addition of the LC filter in the previous converter,a virtual resistor is connected in series on the LC branch to solve this problem.After simulation verification,it can be seen that the addition of the virtual resistor effectively suppresses the current resonance phenomenon.In view of the phase-shift modulation tactics,the voltage and current double closed loop is adopted to control the phase shift angle between the ports to adjust the switching state of the three-port DC-DC converter switch tube,and the PI controller and model predictive controller are introduced to control the isolated three-port DC-DC converter respectively.The stable operation of the system under different conditions guarantees that the electricity storage port is charged and discharged in time to maintain the energy transmission balance of the system.Considering economic issues,the isolated three-port DC-DC converter topology based on phase shift control is proposed and controlled by a PI controller.Simulation is applied to confirm the above model,which proves the availability and accurateness of the two control modes.A hardware experiment platform based on the isolated three-port DC-DC converter is established,and the two control strategies are verified.