| In recent years,with the increasing consumption of traditional fossil energy and the increasing demand of global power,the development and utilization of new energy has entered a rapid development period.However,the access of uncertain power load,such as renewable energy generation device,energy storage device and electric vehicle,not only brings the positive impact of peak load reduction and valley filling,but also brings the challenge of large-scale grid connection.In order to connect it with the traditional power system and realize the multi-directional flow of energy between different voltage levels,the concept of energy router came into being.The bi-directional DC-DC converter in energy router is the key part to realize electrical isolation and bidirectional energy transmission.Therefore,it is of great significance to improve the energy transmission efficiency of bidirectional converter for the optimization of energy router.In this paper,the principle and characteristics of the isolated bi-directional full bridge DC-DC converter(IBDC)are analyzed,and the single phase shift control(SPS),dual phase shift control(DPS),triple phase shift control(TPS)are respectively described.The working mode of each control mode is analyzed in detail by stages,and then the formula is deduced according to the working principle.The mathematical model of transmission power is established.It is clear that IBDC under triple phaseshift control has the maximum power regulation range and the highest flexibility of the system.Based on the theoretical analysis and the mathematical model of the return power,it is known that the return power of the bidirectional full bridge DC-DC converter under the single phase shift control can not be eliminated,which will increase the loss of the switching devices and magnetic components,and reduce the transmission efficiency of the system.The dual phase shift control and triple phase shift control can eliminate the reflux power,so the relationship between the reflux power and the shift ratio under each control mode is analyzed in detail,and the corresponding optimization scheme is established.Finally,through the MATLAB / Simulink platform,a simulation model is built to verify the correctness of the control strategy,and three control methods are compared.The results show that the triple phase shift control can make the output voltage stable at a given value quickly,and the return power is the smallest,and the transmission efficiency is the highest.Finally,a three port energy router model is built by Matlab / Simulink platform.The model has high-voltage grid side port,low-voltage DC load port and low-voltage AC load port.The two-way converter adopts cascade IBDC under triple phase shift control.Three different working conditions are designed for simulation.The results show that when the load changes,the bi-directional converter can realize the bidirectional transmission of energy and its output voltage can be stable at a given value.The energy router can realize the conversion between different voltage levels and AC / DC systems to achieve the power balance. |
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