Research On Dual-Buck Bidirectional DC-AC Converter

Bidirectional DC-AC converter technology of power electronics is one of the most important parts in the research fields,such as the micro-grid,interaction between the electric vehicle and the power gird,and the braking energy regeneration of railway locomotives.The dual-buck inverters have been used to solve the disadvantages of shoot-through,dead-zone design and free-wheeling body-diode of the full bridge topology,and the high efficiency and high reliability of bidirectional converter is implemented.1)Combining with the background of the bi-directional DC-AC conveter,the typical topology structures have been analyzed,and the disadvantages of the conventional bridge circuit have been discussed.The research status of the dual-buck inverter is reviewed,and the advantages of without shoot-through,dead-zone design and free-wheeling body-diode of dual-buck inverter are analyzed in this paper.2)The theoretical and experimental analysis of conventional dual-buck inverter is presented.According to the analysis of dual-buck inverter,infers which have some shortcomings,such as high input bus voltage,poor quality of bipolar modulation waveforms and so on.In order to solve these problems,a two switch dual-buck inverter used into the bidirectional DC-AC converter have been analyzed,the simulations are given,and the common mode current model of the circuit is established.It is concluded that there are without shoot-through and dead-zone design in this structure,but exist the problems of common mode current and large free-wheeling body-diode loss.Therefore,two-switch dual-buck bidirectional DC-AC converter is proposed.To solve the problems of free-wheeling body-diode current and common mode current interference,two independent free-wheeling diode is added into the converter,then the current can not flow through the body-diode and the common mode current loop is shorted.3)The operating principle and the control strategy of the two switch dual-buck bidirectional DC-AC converter are analyzed respectively.In the grid connected inverter mode,using predictive current control to eliminate the impact of grid voltage disturbance,improve the dynamic response speed of the inverter link,and enhance the ability of current tracking reference.In the rectifying PFC mode,the common mode current model of the circuit is eatablished,and the advantage of the low common mode current is obtained;the small signal model of PFC circuit is given,which is used to design the stability of the voltage PI controlled outer loop;the predictive current control strategy is used to enhance the ability of the input current tracking reference,and improve the dynamic performance of the system.4)The parameters of the main power circuit are analyzed in detail and the corresponding design process is given.At the same time,the analysis process of the device selection method and loss calculation is given.The realization of the digital control of bidirectional converter by using the DSP TMS320F28069,the reference design of the bypass auxiliary circuit is added,and the whole system of the prototype is built.Finally,the simulations and experiments of the dual-buck bidirectional DC-AC converter have been completed by the PSIM software built the simulation system and the Altium Designer designed the experimental prototype respectively.The simulation and experimental results demonstrate the feasibility of the theoretical analysis and the design method.