Developed AC/DC/AC Converter Structure Based on Shunt Active Filter and Advanced Modulation Approach for Asymmetrical Cascade H-Bridge Multilevel Inverters
Nabil Karania, Mohamad Alaa Eddin Alali, S. Di Gennaro, Jean‐Pierre Barbot
Abstract
This paper presents a free-harmonic AC/DC/AC converter structure using a novel modulation approach for Asymmetrical Cascade H–Bridge Multi–Level Inverter (ACHB–MLI) and, conventional rectifiers combined with a shunt active filter, for grid integration. The novel approach SMT-SHE combines two modulation techniques: the Staircase Modulation Technique (SMT) and the Selective Harmonics Elimination (SHE). SMT-SHE approach achieves a sinusoidal-like output stepping voltage with variable output voltage amplitude and free of wide band or/and specific harmonics to fulfill the sensitive loads specifications; by determining the appropriate SHE switching angles. The precalculated switching angles are optimized to minimize the number of H–bridge modules and lower the DC capacitors rating. Furthermore, a restriction on the switching angles is proposed to prevent the appearance of undesired harmonics (zeros, even) and consequently overcome the limitation of the SHE algorithm applicability. Finally, a real case study in textile factory is conducted, using real measurements provided by power quality analyzer measuring devices, to validate the proposed AC/DC/AC converter supplying a sensitive load of 50 kVA, given by an asynchronous motor drive.