Optimized Selective Harmonic Elimination for Three-Phase Cascaded Multilevel Inverters with Unequal DC Sources

Ebrahimi, Javad and Nasr Esfahani, Fatemeh and Eren, Suzan and Bakhshai, Alireza (2025) Optimized Selective Harmonic Elimination for Three-Phase Cascaded Multilevel Inverters with Unequal DC Sources. In: 2025 IEEE Energy Conversion Congress & Exposition Asia (ECCE-Asia) :. IEEE, IND, pp. 1-7. ISBN 9798331518875

Abstract

This paper presents a switching technique designed to eliminate specific lower-order harmonics in the output voltage of a three-phase cascaded multilevel inverter with unequal DC voltage sources. Traditional switching techniques focus on selecting switching times to approximate the fundamental sine wave in the output voltage. In three-phase inverters, triple-order harmonics do not appear in the line-to-line voltage, which allows for additional optimization in the switching strategy. The proposed technique incorporates a triple-order harmonic into the fundamental sine wave to enhance harmonic elimination. Furthermore, a method is introduced for selecting appropriate DC voltage source values to regulate the output voltage through DC voltage control. This approach is demonstrated for cascaded multilevel inverters, providing flexibility in source selection and harmonic management. Simulation results confirm that the proposed method effectively eliminates higher-order harmonics, improving output voltage quality. It is important to note that this technique is exclusively applicable to three-phase inverters and is unsuitable for applications that require triple-order harmonics, such as certain operational modes of Dynamic Voltage Restorers.