Bidirectional Three-level Half-bridge DC-DC Converter And Its Extended Phase-shifting Control Strategy

With the widespread use of distributed renewable energy,DC microgrids that are more suitable for distributed energy are gradually emerging.The bidirectional DC-DC converter,as the main connecting device,plays the role of energy exchange and stabilizing the DC bus voltage in the DC microgrid.However,with the expansion of the application range,it faces excessive voltage and current stress,excessive return power,Problems such as large power transmission loss.The three-level half-bridge structure can effectively reduce the voltage stress of the converter switch tube.This article takes the bidirectional three-level half-bridge DC-DC converter as the research goal,and optimizes the phase shift control to improve the work of the bidirectional DC-DC converter.Performance,including reducing converter switch tube current stress,return power and improving efficiency.This article first introduces the current research status of the DC microgrid and its isolated bidirectional DC-DC converter.The research status of the isolated bidirectional DC-DC converter includes topology,four phase shift control methods and multiple control optimization methods.Secondly,analyze the working principle and working mode of the two-way three-level half-bridge DC-DC converter under single phase shift control and extended phase shift control,and compare and analyze the working characteristics of the converter under the two kinds of control.,Which shows that in most transmission power range,the converter performance under extended phase shift control is more superior and the control degree of freedom is high,which is beneficial to the further optimization of peak current and return power.Then,based on the extended phase shift control,the minimum peak current tracking control and minimum return power tracking control methods are proposed.The comparison and analysis with the traditional peak current and return power optimization control methods show that the effectiveness of the proposed optimization control method is established.Corresponding control structure.Next,for the bipolar DC microgrid,a dual input structure is added to the input of the bidirectional three-level half-bridge DC-DC converter,and the voltage transmission ratio switching method is proposed based on the minimum return power tracking control.The voltage of the positive and negative busbars of the polar DC microgrid further reduces the return power of the converter.Finally,a simulation model of the converter is built through the Matlab/Simulink platform,and the working principle of the converter and the optimized control proposed in this paper are simulated and analyzed.At the same time,the main circuit design,control circuit design,auxiliary circuit design and software programming of the proposed bidirectional three-level half-bridge DC-DC converter and dual-input structure are carried out,the converter prototype and experimental platform are built,and the simulation results are carried out.Further experimental verification and analysis,the results show that the minimum peak current tracking control method,the minimum return power tracking control method and the voltage transfer ratio switching method proposed in this paper can effectively optimize the steady-state performance of the converter.