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Multilevel Power Converters Control and Modulation Techniques

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "F: Electrical Engineering".

Deadline for manuscript submissions: closed (10 January 2021) | Viewed by 35613

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Prof. Dr. Concettina Buccella

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Guest Editor

Department of Information Engineering, Computer Science and Mathematics, University of L'Aquila, 67100 L'Aquila, Italy
Interests: modulation techniques and control for multilevel power converters for distributed generation; smart grids; HVDC; multiphase AC drives and other related applications

Prof. Dr. Stefano Di Gennaro

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Guest Editor

Special Issue Information

Dear Colleagues,

The Guest Editors are inviting submissions to a Special Issue of Energies on the subject area of “Multilevel Power Converters Control and Modulation Techniques”.

During the last few decades, multilevel converters (MLC) have drawn the attention of power electronics experts gaining applications and reaching good level of performance and popularity. Until now, research has focused on their utilization in high power applications, such as renewable energy sources, distributed generation, smart grids, and large electric drives; however, due to their excellent overall performance, their diffusion is expected in medium and, in future, in low power applications.

Topologies, control, and modulation represent the main research areas for multilevel converters; however, the scopes of this Special Issue are strictly related to last two aspects, whereas topologies will be considered for a future Special Issue.

Often, MLCs implement control algorithms developed for conventional converters. The modulation technique, instead, is strictly connected with MLC, its application, topology, and adopted power devices. Therefore, one of the main scopes of this Special Issue is to publish original manuscripts specifically developed for multilevel converters.

Depending on application, modulation can operate at low switching frequency, thus with very low switching losses but at the cost of limited dynamic performance or at high or relatively high switching frequency with a pulse width modulation algorithm, therefore achieving high dynamic performance but at the cost of significant switching losses.

This Special Issue will deal with novel control and modulation techniques specifically developed for multilevel power converters. Topics of interest for publication include but are not limited to:

New modulation strategies for multilevel converters;
New digital models for analysis and control of multilevel converters;
Impulsive control techniques for multilevel converters;
Impulsive observation techniques for multilevel converters.

Prof. Dr. Concettina Buccella
Prof. Dr. Stefano Di Gennaro
Guest Editors

Manuscript Submission Information

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Keywords

new modulation strategies for multilevel converters
new digital models for analysis and control of multilevel converters
impulsive control techniques for multilevel converters
impulsive observation techniques for multilevel converters

Published Papers (12 papers)

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14 pages, 6718 KiB

Open AccessArticle

An Efficiency Analysis of 27 Level Single-Phase Asymmetric Inverter without Regeneration

by Eduardo Espinosa, Pedro Melín, Carlos Baier, José Espinoza and Hugo Garcés

Energies 2021, 14(5), 1459; https://doi.org/10.3390/en14051459 - 7 Mar 2021

Cited by 4 | Viewed by 1984

Abstract

For medium voltage applications, multilevel inverters are used. One of its classic topologies is the Cascaded H-Bridge, which requires isolated DC voltages to work. Depending on the DC voltage ratio used in the Cascaded H-bridge can be classified into symmetric and asymmetric. In comparison between symmetric and asymmetric inverters, the latter can generate an AC output voltage with more output voltage levels. DC voltage ratio most documented are binary and trinary. The last can generate an AC voltage of 3ⁿ = 27 levels is obtained, using n = 3 inverters in cascade and NLM modulation, which generates a flow power of the load to the inverters (regeneration). This work analyzes the semiconductor losses (switching and conduction) and the THD of the AC output voltage in function of index modulation, considering a non-regenerative modulation technique for a 27-level single-phase asymmetric inverter. To confirm the theoretical analyzes, simulation and experimental results are shown. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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15 pages, 6156 KiB

Open AccessArticle

Classical Control for Unequal DC Sources Five-Level Inverter-Based SHE Technique

by Mahrous Ahmed, Essam Hendawi, Basem Alamri, Mosleh Alharthi, Farhan Salem, Mohamed Orabi, Saad Mekhilef and Sherif Ghoneim

Energies 2020, 13(18), 4715; https://doi.org/10.3390/en13184715 - 10 Sep 2020

Cited by 2 | Viewed by 1984

Abstract

This study proposes a classical control algorithm for solving the transcendental set of equations for the unequal DC sources of five-level multilevel inverters (MLIs). Such sources can be generated from renewable energy sources. Two DC sources with different values are used to produce an output voltage with five levels. Then, a set of two transcendental equations is formulated with two targeted functions to control the fundamental component and cancel the stipulated single harmonic order. The proposed solution uses a simple classical proportional control with two loops to generate two switching angles. The first switching angle is assigned with an initial value, whereas the second one is calculated from the inner loop. The outer loop is used to cancel the specified harmonic by sending the error signal to the proposed proportional control that tunes the switching angles. The proposed algorithm is easy, fast, and accurate, and has a wide-range solution in terms of modulation index (

MI

) and input DC source ratio (

x = \frac{V_{1}}{V_{2}} \leq 1

). The proposed algorithm is tested for a wide range of

MI

and

x

to verify its feasibility. Moreover, several simulation and laboratory tests are presented to further validate the applicability of the proposed approach. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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20 pages, 5653 KiB

Open AccessArticle

A Generalized Multilevel Inverter Based on T-Type Switched Capacitor Module with Reduced Devices

by Yaoqiang Wang, Yisen Yuan, Gen Li, Tianjin Chen, Kewen Wang and Jun Liang

Energies 2020, 13(17), 4406; https://doi.org/10.3390/en13174406 - 26 Aug 2020

Cited by 5 | Viewed by 2035

Abstract

Conventional multilevel inverters have problems in terms of their complicated expansion and large number of devices. This paper proposes a modular expanded multilevel inverter, which can effectively simplify the expansion and reduce the number of devices. The proposed inverter can ensure the voltage balancing of the voltage-dividing capacitors. The cascading of the T-type switched capacitor module and the step-by-step charging method of the switched capacitors enable the inverter to achieve high output voltage levels and voltage gain. In addition, the inversion can be achieved without the H-bridge, which greatly reduces the total standing voltage of the switches. The nine-level inverter of the proposed topology can be realized with only ten switches, obtaining a voltage gain that is two times larger. The above merits were validated through theoretical analysis and experiments. The proposed inverter has good application prospects in medium- and low-voltage photovoltaic power generation. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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16 pages, 9251 KiB

Open AccessArticle

General Formula for SHE Problem Solution

by Concettina Buccella, Maria Gabriella Cimoroni and Carlo Cecati

Energies 2020, 13(14), 3740; https://doi.org/10.3390/en13143740 - 20 Jul 2020

Cited by 5 | Viewed by 2333

Abstract

This paper considers cascaded H-bridges multilevel inverters with

2^{n}

dc sources, n integer,

n > 0

and proposes a new general formula to compute those

2^{n}

switching angles capable of eliminating

n + 1

harmonics and their respective multiples from the [...] Read more.

This paper considers cascaded H-bridges multilevel inverters with

2^{n}

dc sources, n integer,

n > 0

and proposes a new general formula to compute those

2^{n}

switching angles capable of eliminating

n + 1

harmonics and their respective multiples from the output voltage waveform. The proposed procedure uses only scalar products and avoids linear systems, therefore it has a low computational cost. Computed angles do not depend on modulation index, moreover, voltage sources vary linearly. A mathematical proof is given to validate the formula. Three-phase implementations eliminate or mitigate a significant amount of low order harmonics, thus resulting in very low total harmonic distortion. The proposed formula has been experimentally validated using a single-phase nine-level cascaded H-bridge inverter prototype, resulting in a Total Harmonic Distortion (THD) of 5.59%; the first not-mitigated harmonic is the 17th. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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30 pages, 4300 KiB

Open AccessArticle

Finite Control Set Model Predictive Control for Paralleled Uninterruptible Power Supplies

by Tiago Oliveira, Luís Caseiro, André Mendes and Sérgio Cruz

Energies 2020, 13(13), 3453; https://doi.org/10.3390/en13133453 - 3 Jul 2020

Cited by 6 | Viewed by 2287

Abstract

Nowadays, uninterruptible power supplies (UPS) play an important role in feeding critical loads in the electric power systems such as data centers or large communication hubs. Due to the increasing power of these loads and frequent need for expansion or redundancy, UPS systems are frequently connected in parallel. However, when UPS systems are parallel-connected, two fundamental requirements must be verified: potential circulating currents between the systems must be eliminated and the load power must be distributed between the systems according to UPS systems availability. Moreover, a high-quality load voltage waveform must be permanently ensured. In this paper innovative control strategies are proposed for paralleled UPS systems based on Finite Control Set Model Predictive Control (FCS-MPC). The proposed strategies simultaneously provide: controlled load power distribution, circulating current suppression and a high-quality load voltage waveform. A new dynamic converters deactivation mechanism is proposed. This new technique provides improved overall system efficiency and reduced power switches stress. In this paper, two multilevel based UPS systems are parallel-connected. Each UPS contains two three-level Neutral Point-Clamped-Converters (3LNPC) and a three-level DC-DC converter. The presented experimental results demonstrate the effectiveness of the proposed control strategies in several operating conditions. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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14 pages, 796 KiB

Open AccessArticle

Novel Enhanced Modular Multilevel Converter for High-Voltage Direct Current Transmission Systems

by Dimitrios Vozikis, Fahad Alsokhiry, Grain Philip Adam and Yusuf Al-Turki

Energies 2020, 13(9), 2257; https://doi.org/10.3390/en13092257 - 4 May 2020

Cited by 3 | Viewed by 2435

Abstract

This paper proposes an enhanced modular multilevel converter as an alternative to the conventional half-bridge modular multilevel converter that employs a reduced number of medium-voltage cells, with the aim of improving waveforms quality in its AC and DC sides. Each enhanced modular multilevel converter arm consists of high-voltage and low-voltage chain-links. The enhanced modular multilevel converter uses the high-voltage chain-links based on medium-voltage half-bridge cells to synthesize the fundamental voltage using nearest level modulation. Although the low-voltage chain-links filter out the voltage harmonics from the voltage generated by the high-voltage chain-links, which are rough and stepped approximations of the fundamental voltage, the enhanced modular multilevel converter uses the nested multilevel concept to dramatically increase the number of voltage levels per phase compared to half-bridge modular multilevel converter. The aforementioned improvements are achieved at the cost of a small increase in semiconductor losses. Detailed simulations conducted in EMPT-RV and experimental results confirm the validity of the proposed converter. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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15 pages, 4200 KiB

Open AccessArticle

Tracking Control of Modular Multilevel Converter Based on Linear Matrix Inequality without Coordinate Transformation

by Ming Liu, Zetao Li and Xiaoliu Yang

Energies 2020, 13(8), 1978; https://doi.org/10.3390/en13081978 - 16 Apr 2020

Cited by 5 | Viewed by 2243

Abstract

Modular multilevel converters (MMCs) play an important role in the power electronics industry due to their many advantages such as modularity and reliability. However, one of the challenges is to suppress fluctuations of circulating current and capacitor voltage and to ensure the quality of the output current. In this paper, the upper and lower arm voltages are employed as control inputs to control the output current and circulating current which are fed back to track the desired value. Based on linear matrix inequality (LMI), the control law of the MMC with multi-input system is designed to optimize the control value. The optimum arm voltage is divided by the SM nominal capacitor voltage to determine the number of SMs inserted into the upper/lower arm. The Voltage Sorting Algorithm (VSA) is then used to suppress the capacitor voltage fluctuation. The proposed tracking control strategy is implemented in MATLAB/Simulink. The results show that even under a small number of SMs (4 per arm), the output current can track the desired values and have better harmonic performance (current THD: 5.42%,voltage THD: 5.67%), and the fluctuations of the circulating current can be suppressed. Furthermore, it has better robustness and three-phase variable load fault tolerance. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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16 pages, 8555 KiB

Open AccessArticle

A New Configuration of Three-Level ZSI Using Transistor Clamped Topology

by Santosh Sonar

Energies 2020, 13(6), 1469; https://doi.org/10.3390/en13061469 - 20 Mar 2020

Cited by 1 | Viewed by 2005

Abstract

In this paper, a three-level ZSI (impedance source inverter) based on transistor clamped theory is proposed. It uses the least number of switch counts and associated gate circuitry among all existing topologies of three-level ZSI without any performance degradation. The existing three-level ZSI topologies require three power switches to be turned ON for upper-lower shoot-through (ULST), and four power switches to be turned ON for full dc-link shoot-through (FST). However, with the proposed configuration, upper–lower shoot-through (ULST) and full dc-link shoot-through (FST) is inserted by turning ON only two power semiconductors. A comparison between diode clamped, transistor clamped, and t-type is presented. The proposed topology can realize any of the existing sine-triangle- or space vector-based PWM (pulse width modulation) schemes, and all existing configurations of three-level ZSI can merge into the proposed inverter configuration. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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16 pages, 3539 KiB

Open AccessArticle

Carrier-Phase-Shifted Rotation Pulse-Width-Modulation Scheme for Dynamic Active Power Balance of Modules in Cascaded H-Bridge STATCOMs

by Chen Xu, Jingjing Chen and Ke Dai

Energies 2020, 13(5), 1052; https://doi.org/10.3390/en13051052 - 26 Feb 2020

Cited by 7 | Viewed by 2779

Abstract

In the medium-voltage power distribution system, cascaded H-bridge (CHB) static synchronous compensators (STATCOMs) are widely utilized to solve power quality issues by injecting the controlled reactive current into the system. The carrier-phase-shifted (CPS) pulse-width-modulation (PWM) scheme is preferred for CHB-STATCOMs, because it can minimize the compensating current distortion and realize the relative active power balance among the H-bridge modules. This paper reveals the influence of the carrier phase difference on the module active power balance, and proposes a carrier rotation technique with a CPS-PWM scheme to address this drawback. The rotation rules were analyzed, and the rotation time was especially designed to enhance the robustness of the system. With the proposed method, the natural dynamic active power balance of each module could be achieved, and the capacitor voltage could maintain balance without the individual capacitor voltage control or the auxiliary circuits in theory. The experimental results acquired from a downscaled CHB-STATCOM prototype demonstrated the feasibility of the proposed CPS rotation PWM scheme. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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23 pages, 18068 KiB

Open AccessArticle

Experimental Study on B-Spline-Based Modulation Schemes Applied in Multilevel Inverters for Electric Drive Applications

by Giuseppe Schettino, Guido Ala, Massimo Caruso, Vincenzo Castiglia, Filippo Pellitteri, Marco Trapanese, Fabio Viola and Rosario Miceli

Energies 2019, 12(23), 4521; https://doi.org/10.3390/en12234521 - 27 Nov 2019

Cited by 11 | Viewed by 2010

Abstract

This work presents the design, simulation, and experimental validation of new B-Spline-based modulation techniques applied to a Multilevel Power Inverter (MPI), particularly focusing the attention on the harmonic content of the output voltages of the inverter. Simulation and experimental results are proposed and discussed, mainly describing the potential benefits, such as the increase of the multi-level operation of the converter, and drawbacks (low-order harmonics) related to the adoption of B-Spline functions for multilevel inverters applied in the field of electrical drives. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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16 pages, 7713 KiB

Open AccessArticle

Sector Subdivision Based SVPWM Strategy of Neutral-Point-Clamped Three-Level Inverter for Current Ripple Reduction

by Guozheng Zhang, Bingxu Wei, Xin Gu, Xinmin Li, Zhanqing Zhou and Wei Chen

Energies 2019, 12(14), 2734; https://doi.org/10.3390/en12142734 - 17 Jul 2019

Cited by 5 | Viewed by 2885

Abstract

This paper presents a sector subdivision based space vector pulse width modulation (SVPWM) strategy with reduced current ripple for a three-level inverter. Using the output current ripple theory, closed-form expressions of average current ripple vectors for both continuous and discontinuous switching sequences are derived. Based on the sector and triangle distributions of conventional SVPWM strategy, each triangle is further divided into three small-regions. Then the switching sequence with the lowest magnitude of the average current ripple vector is applied in every small-region, so that the advantages of continuous pulse width modulation (CPWM) and discontinuous pulse width modulation (DPWM) under different modulation index conditions are combined to reduce the current ripple in the whole modulation range. The output performance of the proposed strategy is compared with the conventional CPWM and DPWM strategy, and experimental results verify that the proposed strategy could reduce the current ripple of three-level inverters effectively. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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Review

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0 pages, 8423 KiB

Open AccessReview

An Overview of HVDC Technology

by Neville R. Watson and Jeremy D. Watson

Energies 2020, 13(17), 4342; https://doi.org/10.3390/en13174342 - 21 Aug 2020

Cited by 43 | Viewed by 9673

Abstract

There is a growing use of High Voltage Direct Current (HVDC) globally due to the many advantages of Direct Current (DC) transmission systems over Alternating Current (AC) transmission, including enabling transmission over long distances, higher transmission capacity and efficiency. Moreover, HVDC systems can be a great enabler in the transition to a low carbon electrical power system which is an important objective in today’s society. The objectives of the paper are to give a comprehensive overview of HVDC technology, its development, and present status, and to discuss its salient features, limitations and applications. Full article

(This article belongs to the Special Issue Multilevel Power Converters Control and Modulation Techniques)

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