The Negative Modulation Index: A Key for Augmenting Solutions in Selective Harmonic Elimination and Mitigation Strategies

This article explores the innovative application of the negative modulation index (NMI) as a means to broaden the range of viable options for selective harmonic elimination (SHE) and selective harmonic mitigation (SHM) strategies. Conventionally, the use of a positive modulation index has been standard practice to attain the required magnitudes and phases of fundamental components. However, the research discloses that integrating NMI, which induces phase inversion while preserving magnitude, unlocks additional solutions, particularly in areas previously considered intractable. A critical reassessment of the phase-reversal region is conducted, uncovering its untapped potential for unique solutions. Despite the phase inversion introduced by NMI, the article proposes a novel implementation strategy that retains the original phase. The validity of this approach is established through graphical analysis, simulations in MATLAB/Simulink, and practical implementation on an FPGA-based experimental prototype for two, five, and seven switching angles per quarter. A range of case studies are presented that demonstrate significant enhancements in the SHE and SHM techniques through the utilization of NMI, thereby marking a new phase in the progression of harmonic control methods.