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 $l=2s + 1$ , $s=2^n$ , 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.