1 Department of Energy Technology, The Faculty of Engineering and Science, Aalborg University, VBN2 Power Electronic Systems, The Faculty of Engineering and Science, Aalborg University, VBN3 The Faculty of Engineering and Science, Aalborg University, VBN4 Technical University of Catalonia
This paper presents a novel PWM strategy for nlevel three-leg semiconductor-clamped dc-ac converters in the overmodulation region, with dc-link capacitor voltage balance in every switching cycle. The strategy is based on the virtual-vector concept. Suitable reference vector trajectories are selected to obtain low weighted total harmonic distortion and a simple algorithm. A hexagonal-boundary compression factor is introduced to guarantee, at any operating point, dc-link capacitor voltage regulation capabilities in every switching cycle and avoid narrow gate pulses. The detailed PWM algorithm for an easy implementation in a digital control platform is also presented. The good performance of the strategy is verified through both simulation and experiments in a three-level threephase neutral-point clamped converter.
I E E E Transactions on Industrial Electronics, 2013, Vol 60, Issue 5, p. 1872-1883