Research On Transient Dc Bias Suppression Of Dual Active Bridge DC-DC Converter

Dual Active Bridge(DAB)DC-DC converters have been widely used due to their unique operating mode and excellent performance.Phase-shift control is commonly used to control power transmission in DAB converters.Due to the inability to meet the theoretical prerequisites for steady-state analysis during the phase-shift value update and adjustment process,transient DC bias occurs.Compared to steady-state optimization and dynamic control,transient DC bias has received less attention.Aiming at the transient DC bias problem under phase-shift control,this paper focuses on two specific topologies,traditional DAB converter and three-level DAB converter,and conducts research on transient DC bias suppression strategies.Firstly,the principle of phase-shift control and steady-state operating characteristics of DAB converters are analyzed,with emphasis on classifying the operating modes under triple-phase-shift control.At the same time,based on the phase-shift principle and current characteristics,the transient DC bias phenomenon and transient power transmission characteristics of DAB converters are briefly analyzed.Then,a transient suppression strategy based on dual equivalent decoupling is proposed for the transient DC bias problem of traditional DAB converters.A new classification concept is proposed based on the relationship between switching signals and carrier timing positions,and a quantitative model of transient current is established.The transient DC bias under the equivalent action of each phase-shift value is processed through dual equivalent decoupling,and transient suppression is achieved through half a cycle.Transient adjustment constraints and actual switching signal generation are analyzed.The effectiveness of the strategy is verified through simulation.Further,a transient suppression strategy based on carrier symmetric update is proposed for the transient DC bias problem of three-level DAB converters.By analyzing the operational constraints of five-level modulation,a general constraint condition for transient suppression adjustment of three-level DAB converters is defined.Adjust the equivalent symmetrical neutral position of the output voltage waveform on the three-level full-bridge side,and use equivalent decoupling suppression on the two-level full-bridge side.Transient suppression is achieved through half a cycle.Based on the carrier symmetric update strategy,the operating characteristics of the current are analyzed,and a quantitative transient current model is established.The effectiveness of the strategy is verified through simulation.Finally,an experimental verification of the proposed strategy is carried out.By designing and constructing experimental prototypes,the effectiveness of the transient DC bias strategy is verified,which can effectively reduce current overshoot and achieve transient DC bias suppression.