## 1 Introduction  
In order to achieve lower harmonic content in the output waveforms and lower filtering requirements at the grid side, multi-level inverters would have been the future trend in grid integration applications. To boost the efficiency and performance of grid-connected systems, multi-level inverters would have been integrated into renewable energy applications. Recently, a topology, that is, the modular multilevel converter (MMC) evolved from the multi-level family that has a profound application in photovoltaics, offshore, onshore wind energy, and medium voltage motor drives STATCOM, and UPQC, etc. The advantages of MMC are handled for high voltage applications, compact construction, stability, and reliability, whereas the PV is integrated into the grid. We could see some special characteristics like peak power capacity, fault ride-through, power quality, and higher redundancy capabilities popularly in MMC PV-based inverters [1]. One of the key topics that has been in current research is how to improve the efficiency and performance of photo-voltatic systems in the field of advanced power electronics for the energy conversion stages. There are various publications directed toward improvements and future implementation areas of before and after MMC studies. Many of those studies mostly focused on the various sub-module arrangements. The idea of a unidirectional sub-module has been explored in [2]. The efficiency of the MMC has been tested and compared to traditional two-level cells using various cell configurations, such as neutral point clamped and flying capacitor topologies. DC-MMC-based systems have been used as PV conversion systems with two stages with MMC-based HVDC [3, 4], where high irradiance is available at longer distances from the consumption centers. Generally, in some MMC-based PV systems, it is required to provide each dc-dc converter without independent MPPT to supply for the SM capacitor balance, which in turn helps in constant production of output required voltage levels without any power fluctuations [5]. Having said that, by maintaining lossless energy conversion, we have had MV grid integration of PV using MMC [6], because the individual MPPT arrangement in MMC and multi-string central inverter have lower MPPT losses when compared to a central inverter. In addition, a high-power hybrid-MMC was used for PV grid integration to provide reliable performance, even though under partial shading condition, because of the presence of individual MPPTs in each SM [7]. Thus, some of the MMC-based PV-BESs (photovoltaic-battery energy storage systems) [8] and energy distribution areas [9] had also been potential options for handling power mismatches and smoothening the output power. In addition, for applications where high power and medium voltage requirements, we can have some topologies of inverters without any need for the line-frequency transformer are given in [10]. The organization of the paper is as follows: Section 1 deals with the introduction. Section 2 explains the MMC and its submodule variants. Section 3 details the control of MMC. Section 4 illustrates the modulation strategies for MMC. Section 5 discusses the results. Finally, the paper is concluded in Section 6.