DC Link Voltage Balancing Technique Utilizing Space Vector Control in SiC-based Five-Level Back-to-Back-Connected NPC Converters

Paper in proceeding, 2018

This paper presents an improved voltage balancing algorithm of the dc-link capacitors in an electric drive with back-to-back connected five-level neutral-point-clamped (NPC) converters. A properly modified space-vector-pulse-width-modulation (SVPWM) algorithm is developed, which balances the capacitor voltages effectively by utilizing the redundant states of the space vector plane. The dc link voltage balancing is attained by the proper control of the NPC converters without requiring any additional hardware and, thus, the cost of the electric drive can be minimized. This paper presents the theoretical analysis of the proposed voltage balancing technique for all the operating conditions of the converters. A 50kW electric drive is simulated on Matlab/Simulink and modelled using PLECS in order to accurately calculate the losses of the converters. SiC power switches are used for the prototypes of the 5-level NPC converters. Selective experimental results are also shown.