Low Computational Cost SHE Procedure in Cascaded H-Bridge Inverters for Real-Time Applications

An analytical formula, applicable to l-level Cascaded H-bridge (CHB) inverters with l = 2s + 1, s = 2n, number of DC sources, is proposed for computing the switching angles of the converter, which allows n harmonics and their multiples to be eliminated from the output voltage waveform while imposing the amplitude of the fundamental harmonic. To reduce the computational cost of the arccos function in the switching angles formula, it is expressed using first- and second-degree least squares polynomials. The proposed analytical selective harmonics elimination (SHE) procedure has been validated on a nine-level cascaded H-bridge inverter with four DC sources and switching angles in single-phase and three-phase configurations. An experimental setup was built and the results obtained were compared with those from simulation, revealing good agreement.