Modular Multilevel Converters for Large-Scale Grid-Connected Photovoltaic Systems: A Review

Abstract

The use of photovoltaic (PV) systems as the energy source of electrical distributed generators (DG) is gaining popularity, due to the progress of power electronics devices and technologies. Large-scale solar PV power plants are becoming the preferable solution to meet the fast growth of electrical energy demand, as they can be installed in less than one year, as compared to around four years in the case of conventional power plants. Modular multilevel inverters (MMIs) are the best solution to connect these large-scale PV plants to the medium-voltage (MV) grid, due to their numerous merits, such as providing better power quality, having higher efficiency, providing better reliability, and their scalability. However, MMIs are still progressing and need some improvement before they can be implemented safely in the industrial, medium, and high voltage networks. The main purpose of this paper is to review the present MMIs topologies when used in PV applications. The review aims to present a comprehensive study of the various recent submodule circuits associated with MMI topologies. Maximum power point tracking (MPPT) control schemes for PV inverters will be explored extensively. Then, the different control strategies of PV MMIs will be presented and compared to give a holistic overview of the submodules balancing techniques, ranges, and capabilities under balanced and unbalanced grid conditions. In addition, the paper will discuss the future of PV MMIs systems in electricity networks.

Power Converter Topologies for Grid-Tied Solar Photovoltaic (PV) Powered Electric Vehicles (EVs)—A Comprehensive Review

“…Therefore, in EV fast and ultra-fast charging applications, multilevel converters (MLCs), including Cascaded H-Bridge (CHB) [46,47], Flying Capacitor (FC) [48,49], and Neutral Point Clamped (NPC) [50][51][52][53] converters have been preferable in some publications (see Figure 12). Their outstanding advantages include low THD, smaller dv/dt, minimized magnetic components, less voltage stress across the semiconductor devices in high-voltage applications (e.g., 100 V rated switches within the 400 V voltage battery range), low electromagnetic interference (EMI), and a low rated switch, in addition to reduced voltage transition between levels [132][133][134][135][136][137][138][139][140][141][142][143]. However, reliability, voltage balancing, high cost, and complex structure and control are some concerns related to MLCs.…”

A Review on Power Electronic Topologies and Control for Wave Energy Converters

“…Several research papers considered the design and the control of modular and cascaded configurations instead of the conventional back-to-back converter in different RESs including PV and WTs [68][69][70][71][72][73][74][75][76][77][78][79][80]. Taking the large-scale PV (LSPV) systems, for example, modular converters emerged as a promising candidate where the power conversion stage is formed from several submodules (SMs) instead of one bulky centralized power converter.…”

An Improved Sliding Mode Control with Integral Surface for a Modular Multilevel Power Converter

“…Due to its feature, this converter is suitable for medium-and high-voltage applications, e.g., high-power motor drives [7], high-voltage direct current transmission (HVDC) [8], unified power flow controller (UPFC) [9], and static synchronous compensators (STATCOM) [10,11]. Moreover, for gridconnected PV systems [12], modular multilevel inverters are the preferred solution to connect large-scale PV plants [13] to the medium-voltage (MV) grid because then the costly and bulky transformer can be removed.…”