Testbench Converter to Validate Control Algorithms for a High-Cell-Count Cascaded H-Bridge System

Abstract:
This work presents aspects on the design process of the converter cell used in a specific cascaded H-bridge converter. This known modular multilevel converter topology is often proposed for battery electric storage systems intended to be used in the medium voltage grid. For the test of control strategies, fault tolerance, communication solutions and to address further issues, like cell-balancing, a hardware demonstrator is in development, based on the converter cell described in this work. The paper will go into details about the specification of the hybrid DC link, which consists of batteries and capacitors in parallel. In addition, simulations and measurements of the current sharing between batteries and capacitors are presented. Furthermore, the selection process of the MOSFETs and suitable driving circuit will be described, as a fact that the cell hence is operated at a rather low voltage level of 3 to 4.2 V.