Research On Control Mode Of Bidirectional Full-bridge DC-DC Converter

With less and less available fossil energy,the requirements for research and application of new energy technologies are becoming more and more urgent.At present,accelerated research in photovoltaic power generation systems,microgrids,power electronic transformers and electric vehicles is to improve the energy structure.A very good way.However,the problem of photovoltaic power generation is that it is greatly affected by the weather environment and the output voltage is unstable.It needs to be combined with an energy storage device with adjustment capabilities and a module circuit that can allow bidirectional energy flow.Compared with ordinary transformers,power electronic transformers have the advantage of being able to complete reactive power compensation to reduce grid harmonics,and have their own protection functions,without the need to install other relay protection devices.The two-way full-bridge DCDC circuit plays an important role in the electronic electronic transformation.For electric vehicles,the energy bidirectional flow device is used to feed back the kinetic energy when the vehicle is braking to the vehicle battery,which greatly improves the working efficiency of the electric vehicle.These applications require high power density bidirectional DC-DC converters as energy flow control devices.The isolated bidirectional full-bridge DC-DC circuit can flow energy in both directions,and the power density of the circuit is high.Due to the characteristics of the circuit structure,the switch tube is easy to realize soft switching during operation,so it has been widely used in many occasions.The traditional control method of the bidirectional full-bridge DC-DC converter is single-phase shift control.This control method has big problems in some cases,such as when the circuit is working at a voltage transfer ratio that is not equal to 1.There will be a large return power,which means that the current needs to be increased when the same power needs to be transmitted.Increase the loss of the device,which is obviously not conducive to the working efficiency of the circuit.Therefore,it is very necessary to improve the control method of the bidirectional full-bridge DC-DC converter to improve the operating characteristics of the circuit.This article first explained the working principle of the circuit under SPS control and DPS control,and detailedly described the current conditions of each stage of the circuit under the two control modes.According to the characteristics of the inductance,the current expression of each stage was deduced,and then calculated The current characteristics and power characteristics of the circuit under the two control modes are presented,and the working range of the circuit soft switch under the corresponding control mode is analyzed.Although the current stress and return power under DPS control are reduced compared to those under SPS control,the effect is still not good.In this paper,the derivation of Lagrangian equations proposes that in addition to a hybrid control method,the current stress and return power of the circuit under this control method are significantly reduced,and the circuit’s anti-interference performance is also better.In this paper,the SPS control mode,the DPS control mode and the hybrid control mode are obtained through the simulation of the inductor current waveform and the return power waveform.Through the comparison between the waveforms,it is found that the results are basically consistent with the theoretical derivation.The current stress and return power in the case of hybrid control are significantly reduced,which improves the working efficiency of the circuit.At the end of the article,an experimental prototype was also made,and the actual waveforms obtained from debugging also verified the correctness and feasibility of the theory.