Advanced graphical and sliding mode techniques for enhanced selective harmonic control in two level inverters

Abstract

Harmonic distortion in power electronic converters significantly affects power quality, posing challenges in meeting standards like IEEE 519-2022. This thesis presents several novel approaches to Selective Harmonic Elimination (SHE) and Selective Harmonic Mitigation (SHM), emphasizing the reduction of Total Harmonic Distortion (THD) and optimizing two-level inverter performance. First, a novel graphical method for SHM is introduced, offering a straightforward and computationally efficient means of mitigating multiple harmonics simultaneously. By simplifying the identification of optimal switching angles, this approach achieves significant THD reductions and meets grid standards. The graphical framework also adapts well to systems with variable DC voltages, making it highly applicable to renewable energy systems. The thesis then introduces a Second-Order Twisting Sliding Mode Control (SOT-SMC) technique for SHE, which formulates harmonic elimination as a sliding manifold problem. This method efficiently eliminates target harmonics without inducing chattering and computes switching angles in less than 1.5 µs, making it ideal for real-time applications in dynamic power systems. Further extending SOT-SMC to SHM, the approach mitigates a wider range of harmonics while using fewer switching angles, compared to traditional methods. This enhancement results in reduced THD and improved system efficiency. Lastly, the thesis explores the use of a Negative Modulation Index (NMI) in both SHE and SHM, unlocking new harmonic elimination solutions. The NMI approach allows for greater flexibility in harmonic control by leveraging phase inversion techniques to correct for negative modulation, leading to enhanced harmonic performance and reduced THD. All proposed methods are rigorously validated through simulations and experimental testing using an FPGA-based hardware prototype, demonstrating their effectiveness and potential for real-world applications in power converters and renewable energy systems.