An Enhanced Low Switching Frequency Modulation-Based Symmetric Multi-Level Inverter for Harmonic Mitigation

Multi Level Inverter (MLI) converts DC into nearsinusoidal AC with low Electro Magnetic Interference (EMI) and component stress, making them appropriate for medium and high-voltage applications like Renewable Energy Systems (RES). This study presents an enhanced Low Switching Frequency Modulation (LSFM) approach for an MLI to efficiently provide high-quality output voltage for mediumpower applications. The LSFM-based MLI produces a stepped voltage waveform that closely approximates a sinusoidal, lowering Total Harmonic Distortion (THD) and improving overall system performance. A new switching angle calculation approach for the proposed modular MLI is presented. The suggested method eliminates initial guessing in switching angle computation and guarantees ideal switching angles for minimal THD. In contrast to previous methods, this approach solves difficult transcendental equations and optimizes switching angle calculations. Its THD reduction potential and computational efficiency are compared to the Nearest Level Modulation (NLM) switching algorithm. The THD values for 5, 9, 15 and 25 level inverters are found to be 17.06%, 8.82%, 4.97% and 2.73% using NLM, whereas for LSFM scheme 16.39%, 8.38%, 4.97% and 2.66% were obtained. The simulation outcomes ensure the efficacy of the proposed system in mitigating the harmonics compared to traditional methods.