DC link balancing and ripple compensation for a cascaded-H-bridge using space vector modulation

Abstract

This paper presents a modulation scheme for the cascaded H-bridge multi-level converter based on space vector modulation. The method is modified from other implementations in two ways. Switching states are chosen to keep the d.c. link voltages on each bridge equal and a modified co-ordinate transformation is employed to compensate for d.c. link voltage ripple. A constraint for minimal switching is obeyed causing only one bridge to commutate between two consecutive switching states in steady state. The algorithm can be extended to a greater number of levels with minimal modification and minimal additional computational cost.