The DAB-DC/DC Converter Based On Digital Predictive Current Mode Control

The University of Wisconsin Madison first proposed dual-active-bridge(DAB)DC/DC converters.Since then,the DAB-DC/DC converter has developed rapidly.It has the advantages of high power density,wide load range,easy soft switching,high frequency isolation and energy flow bidirectional.It has rapidly used in the field of electric vehicles,uninterruptible power supply(UPS)Micro-grid and so on.In order to improve the response speed of the converter and control the DC bias in the high-frequency inductor current of the transformer,the control algorithm of the converter has been studied in this paper.Traditional closed-loop control often uses voltage closed-loop control or average current mode control.The former can not control the inductor current,which resulting in transformer inductor current DC bias while transient process.the latter voltage loop PI controller response speed limited by the current loop PI controller,resulting in the limitation of converter’s dynamic response.In order to solve these problems,this paper proposes a predictive current mode control algorithm based on Half Switching Cycle Middle Sampling(HSCMS).Based on the inductor current ripple,this method predicts the circuit control variable of the next cycle according to the control variable of this control cycle and the necessary circuit parameters so that the current loop’s response speed has been increased to one switching cycle,thereby the response speed of the voltage loop is greatly improved.At the same time,by controlling inductor’s current on the mid-point of the half switching cycle,the DC offset during transient conditions can be quickly eliminated.In this paper,the working principle of the control algorithm is expounded firstly,the algorithm expression is deduced in detail,and the control performance of the algorithm for DC bias problem is analyzed in detail.Then,this paper established a small signal model of DAB-DC/DC converter,designed the digital controller of the converter.The simulation model is established and the correctness and effectiveness of the proposed control algorithm are verified.Finally,this paper introduces the design of DAB-DC/DC converter experimental platform.The design of hardware and software are introduced respectively.The digital control system of DAB is designed and the low power experiment platform is set up.The experimental verification of current mode control algorithm based on HSMCS is carried out.In order to further study the DAB-DC/DC converter digital current mode Control provides the technical basis.