Abstract: Day by day, the popularity of multi-level inverters (MLIs) for applications of high power and high voltage is growing. These MLIs, including solar photovoltaic (PV) systems, are being built into the grid for renewable energy extraction. The MLI induces a low harmonic material staircase output voltage and can pump a sinusoidal grid current with an increased power factor. The MLI-based grid-tied PV system will therefore work with reduced filter requirements at the lower switching frequency. The numerous MLIs, modulation, and control techniques for grid-connected applications are discussed in this article. A detailed classification of different grid-connected Multi-level inverters (GCMLIs) based on the number and arrangement of DC voltage sources is presented. For various MLI-based PV systems that communicate with the utility grid, various control techniques and modulation techniques have also been addressed. For a deeper understanding and reliability of past and future PV system technologies, this paper also provides detailed comparisons and discussion of different control techniques used in single-phase and three-phase grid-connected MLI.

                    Keywords: Multi-level inverter (MLI), Solar Photovoltaic (PV), Control techniques, Modulation strategies, Grid-connected Multi-level inverters (GCMLIs)