Converters with AC transformer intermediate link suitable as interfaces for supercapacitor energy storage

Abstract

The paper considers a problem of construction, control and design of converters designed as interfaces between supercapacitor energy storage battery with maximal voltage not higher than 100 V and DC link with voltages corresponding to standard grid voltage (over 600 V). The main feature of this type of converters is the presence of an intermediate AC medium frequency link with transformer permitting the direct voltage fitting. Two types of the converter are investigated showing advantages and disadvantages of both solutions. As more promising the solution with voltage type intermediate DC link on low voltage side has been analyzed and tested in details. The matching of DC capacitance with AC- stray inductance together with proper phase synchronization of DC power controlling converter with AC link voltage permit to obtain a better power factor of DC/AC/DC converters and lower capacitor current, which improved efficiency ensuring the good dynamic. The investigation of the converter circuit and its control is done with the use of exact simulation model and verified on laboratory bench with MOS and IGBT converters and ferrite core transformer.