Research On AC/DC Converters Based On Three-Port Rectifiers And Sigma-Output Configuration

AC/DC converters are key interface between the main AC grid and various DC loads and have been widely used in electric vehicle charger,energy storage,smart-grid and power supplies for data center,etc.As DC voltage of load varies in a wide range and amount of input harmonic current is restricted by relevant power quality standads,AC/DC converters are required to achieve flexible DC voltage regulation and high input power factor.In addition,high efficiency should be guaranteed over the whole range.In order to meet these requirements,novel AC/DC converter with high efficiency based on Three-Port Rectifier(TPR)and sigma-output configuration is researched in this paper.Firstly,system architecture of the AC/DC converter based on TPR and sigma-output configuration is reserached.By building another power path on traditional rectifiers,TPRs which are composed of an AC input port and dual DC output ports are obtained.Different connection methods are applied to the TPR and DC/DC converter which can be divided into two constructions,i.e.output current and voltage sigma constructions.Control strategy to regulate the dual port voltages and input current in the two constructions is analyzed,respectively.The AC/DC converter with output current-sigma configuration is firstly taken as an example to analyze the operating principle,characteristic,modulatin and control method in detail.Theoretical analysis indicates that most of the input power can be directly supplied to the load within single-stage power conversion,which means equivalent conversion stage can be reduced.In addition,the power losses,switches’ voltage and current stresses of the DC/DC converter can also be reduced significantly.Experiment results prove the theoretical analysis.Furtherly,operation principle,characteristics and control method of the AC/DC converter with output voltage-sigma configuration are researched in detail.Multi-mode control strategy is adopted to realize the power distribution between the dual DC ports.Mode transition control strategy based on the volt-second balance of the inductor ensures smooth transition can be achieved.Output DC voltage can be directly regulated by the TPR.Therefore,the downstream DC/DC converters can always work around the optimized operation conditions.Design methods for the critical paraments and models of the control loop are analyzed.The feasibility and effectiveness of the researched converter is fully verified by the experimental results from a 2kW prototype.