MIXED-NORM SWITCHING-ANGLE OPTIMIZATION FOR HARMONIC REDUCTION IN CASCADED H-BRIDGE MOTOR DRIVES
Arwa Aldbies, Adnan Alahmad, Adil Adam
Abstract: Cascaded H-bridge Motor Drives (CHBMD) are attractive for medium-voltage motor drives because of their modular structure, reduced semiconductor voltage stress, and ability to generate high-quality output waveforms. However, conventional modulation and selective harmonic elimination methods may not simultaneously maintain the required fundamental voltage and suppress a broad range of low-order harmonics, while high-frequency pulse-width modulation increases switching losses. This study proposes a mixed-norm switching-angle optimization method for improving the harmonic performance of CHBMD. The method combines a fourth-order normalized fundamental-voltage error term with a quadratic harmonic-distortion term to balance voltage regulation and harmonic reduction. The optimization problem is formulated using Fourier-based harmonic modeling and switching-angle constraints, and four conventional objective functions are used as performance benchmarks. The proposed method is evaluated in MATLAB/Simulink and experimentally validated using the same three-phase eleven-level CHBMD topology under fully identical operating conditions. Simulation results show that the proposed objective function achieves a minimum voltage total harmonic distortion of 6.93%, outperforming the evaluated benchmark formulations. The method also maintains stable harmonic performance over a modulation-index range of approximately 0.70–1.00. Experimental results demonstrate a reduction in voltage distortion from 8.6% with conventional sinusoidal pulse-width modulation to 3.3% with the proposed strategy. The findings confirm the effectiveness of the method for low-switching-frequency CHBMD. The present validation is limited to a low-power prototype under fixed operating conditions.
Keywords: Selective harmonic elimination, Multilevel converters, Medium-voltage drives, Fourier harmonic modeling, Objective-function optimization, Total harmonic distortion
DOI: 10.24874/PES08.03B.004
Recieved: 27.02.2026 Revised: 03.06.2026 Accepted: 01.07.2026
UDC:
Reads: 7 
