International Journal of Scientific Research and Engineering Development

The efficiency of power conversion systems is critical to the global transition toward decentralised renewable energy grids. This paper presents a comparative analysis of three modulation strategies applied to a three-phase, five-level Neutral Point Clamped (NPC) inverter in a grid-tied photovoltaic (PV) context: Phase Disposition Sinusoidal Pulse Width Modulation (PD-SPWM), Space Vector Pulse Width Modulation (SVPWM), and Selective Harmonic Elimination (SHE). All techniques are implemented in MATLAB/Simulink environment and evaluated against IEEE 1547 and IEC 61727 standards using Total Harmonic Distortion (THD), DC-bus utilisation (Voltage Utilisation Factor, VUF), and Common-Mode Voltage (CMV) suppression as primary metrics. A key finding is that, under the LCL filter optimised for the carrier-based methods, five-level SVPWM does not meet the IEEE 1547 THD limit, yielding an 8.43% filtered THD; a sensitivity analysis (Section IV.F) shows this non-compliance is filter-bound rather than intrinsic to the modulation strategy. PD-SPWM achieves the lowest filtered THD of 1.01% and the highest VUF of 49.75%, while SHE achieves 2.69% THD, the lowest peak CMV of ±72 V, and the lowest switching frequency of 450 Hz, making it thermally optimal. This trivariate comparison, THD, CMV, and VUF measured simultaneously across all three strategies under an identical five-level NPC topology, consolidates within a single model metrics that prior work has examined only separately or in pairs. SHE is recommended as the thermally optimal strategy for utility-scale PV systems; PD-SPWM is recommended where power quality is the primary constraint.

J. Ozuem, "Comparative Analysis of Modulation Techniques for Five-level Inverters in Grid-Tied Photovoltaic Applications" International Journal of Scientific Research and Engineering Development, V9(4): Page(179-186) May-June 2026. ISSN: 2581-7175. www.ijsred.com. Published by Scientific and Academic Research Publishing.