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Modular Multilevel Converter for Photovoltaic Applications

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A2: Solar Energy and Photovoltaic Systems".

Deadline for manuscript submissions: closed (1 June 2022) | Viewed by 10737

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Special Issue Editor

Dr. Ahmed Darwish

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Guest Editor

School of Engineering, Lancaster University, Lancaster LA1 4WY, UK
Interests: renewable energy system; power quality; DC/DC converters; electric vehicles; multilevel converters
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The consumption of fossil fuels is leading to increasing concerns about the environment and is pressing for more efforts to promote renewable energy sources. Solar photovoltaic (PV) systems are a promising solution to replace the coal, oil and natural gas electricity generators, especially when they are close to reaching price parity. Multi-megawatt large-scale PV electricity plants became a favourable choice for meeting the rapid growth in electrical demands, as they can be installed in a short period (6–12 months). Large-scale PV power plants are expected to have power higher than 5 MW and can be connected directly to medium voltage networks. To achieve this, modular multilevel converters (MMCs) are expected to play an important role in these PV power farms, in order to build compact and efficient power conversion systems. The aim of this Special Issue is to receive scientific contributions regarding large-scale PV power systems in terms of new modular power converters, stability analysis, design and control of modular converters in the context of PV energy systems, and grid support functions from PV plant systems, as well as other similar topics.

Dr. Ahmed Darwish
Guest Editor

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Keywords

Modular converters
Photovoltaic energy sources
DC/AC inverters
Grid support functions
Power electronics control

Published Papers (4 papers)

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Research

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25 pages, 10156 KiB

Open AccessArticle

PV/Battery Grid Integration Using a Modular Multilevel Isolated SEPIC-Based Converter

by Fatemeh Nasr Esfahani, Ahmed Darwish and Ahmed Massoud

Energies 2022, 15(15), 5462; https://0-doi-org.brum.beds.ac.uk/10.3390/en15155462 - 28 Jul 2022

Cited by 5 | Viewed by 1478

Abstract

Photovoltaic (PV) plants can be built rapidly when compared with other conventional electrical plants; hence, they are a competent candidate for supplying the electricity grid. The output power of the PV modules can be used in plug-in electric vehicles (PEVs) DC charging stations to reduce the burden on the electricity grid, particularly during peak load hours. To integrate PV modules and electric vehicles (EVs) with the electricity grid, the modular multilevel converters (MMCs) topologies producing staircase voltage waveforms are preferred as they are able to deliver less total harmonic distortion (THD) and higher efficiency in addition to lower voltage stress on semiconductor switches. In conventional centralized MMC topologies, a direct connection to a high-DC-link input voltage is required which is not appropriate for PV plants. A new MMC topology for PV/EV/grid integration is proposed in this paper, where the individual PV arrays are directly connected to each phase of the AC grid to harvest the maximum available power point. A current-source converter (CSC) based on a single-stage isolated SEPIC converter is adopted as the submodule (SM) for the proposed MMC topology given its outstanding features, such as low input ripple current, high efficiency, high power factor, and flexible output voltage higher or lower than the input voltage. The single-stage SMs can operate in both DC/DC and DC/AC operating modes. Proper controllers for each mode of operation are designed and applied to supply constant current from either the PV modules or the battery cells by eliminating the second-order harmonic component. The performance of the proposed converter is verified by simulations and a downscaled prototype controlled by TMSF28335 DSP. Full article

(This article belongs to the Special Issue Modular Multilevel Converter for Photovoltaic Applications)

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18 pages, 6176 KiB

Open AccessArticle

Dual Isolated Multilevel Modular Inverter with Novel Switching and Voltage Stress Suppression

by Saud Alotaibi, Xiandong Ma and Ahmed Darwish

Energies 2022, 15(14), 5025; https://0-doi-org.brum.beds.ac.uk/10.3390/en15145025 - 09 Jul 2022

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Abstract

This paper presents an improved structure for the submodules (SMs) in the three-phase modular inverter (TPMI) based on a dual isolated SEPIC/CUK (DISC) converter for large-scale photovoltaic (LSPV) plants. The DISC SMs can offer several advantages, including increased efficiency, reduced passive elements, and galvanic isolation via compact-size high-frequency transformers. The SMs can also provide a wide range for the output voltage and draw continuous currents with low ripples from the input source. However, the high dv/dt value across the switches during hard switching can cause current oscillations and voltage spikes, which will impair the operation of complementary switches and affect the safety of the power devices. For this challenge, the DISC SM is improved by replacing the output switches with diodes and adding a bypassing switch. In comparison to the conventional DISC SM, the improved DISC SM reduces the switch’s voltage spikes; hence, it can increase the overall efficiency. Thus, the DISC SM’s will be able to suppress voltage spikes in the TPMI inverter and therefore the total reliability will be improved. The work will detail the analysis of the proposed system along with design guidelines. Additionally, the simulation and experimental results to validate the operation of proposed DISC SM are presented using MATLAB/SIMULINK as well as a scaled-down experimental prototype. Full article

(This article belongs to the Special Issue Modular Multilevel Converter for Photovoltaic Applications)

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Review

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28 pages, 6940 KiB

Open AccessReview

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

by Fatemeh Nasr Esfahani, Ahmed Darwish and Barry W. Williams

Energies 2022, 15(13), 4648; https://0-doi-org.brum.beds.ac.uk/10.3390/en15134648 - 24 Jun 2022

Cited by 22 | Viewed by 3329

Abstract

The transport sector generates a considerable amount of greenhouse gas (GHG) emissions worldwide, especially road transport, which accounts for 95% of the total GHGs. It is commonly known that Electric vehicles (EVs) can significantly reduce GHG emissions. However, with a fossil-fuel-based power generation system, EVs can produce more GHGs and therefore cannot be regarded as purely environmentally friendly. As a result, renewable energy sources (RES) such as photovoltaic (PV) can be integrated into the EV charging infrastructure to improve the sustainability of the transportation system. This paper reviews the state-of-the-art literature on power electronics converter systems, which interface with the utility grid, PV systems, and EVs. Comparisons are made in terms of their topologies, isolation, power and voltage ranges, efficiency, and bi-directional power capability for V2G operation. Specific attention is devoted to bidirectional isolated and non-isolated EV-interfaced converters in non-integrated architectures. A brief description of EV charger types, their power levels, and standards is provided. It is anticipated that the studies and comparisons in this paper would be advantageous as an all-in-one source of information for researchers seeking information related to EV charging infrastructures. Full article

(This article belongs to the Special Issue Modular Multilevel Converter for Photovoltaic Applications)

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30 pages, 5824 KiB

Open AccessReview

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

by Saud Alotaibi and Ahmed Darwish

Energies 2021, 14(19), 6213; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196213 - 29 Sep 2021

Cited by 22 | Viewed by 3647

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. Full article

(This article belongs to the Special Issue Modular Multilevel Converter for Photovoltaic Applications)

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