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MVDC Grids: Modelling, Design, Power Converters, Stability, Control and Operation

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

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 11407

Special Issue Editors

Research Group in Electrical Technologies for Sustainable and Renewable Energy (PAIDI-TEP023), Department of Electrical Engineering, Higher Polytechnic School of Algeciras, University of Cadiz, Algeciras, Spain
Interests: smart grids; microgrids; renewable energy; wind energy; photovoltaic solar energy; energy storage systems; hydrogen and fuel cells; hybrid electric systems; electric vehicles; electric power systems; power converters and energy management/control systems
Special Issues, Collections and Topics in MDPI journals
Department of Electrical Engineering, University of Jaén, Jaén 23071, Spain
Interests: power systems; modeling; renewable energy
Department of Electrrical Engineering, Escuela Técnica Superior de Ingeniería Industrial de Barcelona (ETSEIB), Universidad Politécnica de Cataluña (UPC), Spain
Interests: power quality, harmonics, voltage sags, unbalances, impedance-based stability criteria, grid-connected converters
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We would like to invite original research or review articles to our Special Issue on the topic of "MVDC Grids: Modelling, Design, Power Converters, Stability, Control and Operation" in our Energies journal.
The Medium Voltage Direct Current (MVDC) grid is a new grid concept that can be used as an additional stage of infrastructure in the electrical network between transport and distribution levels, as well as a means of supplying consumers of commercial, residential, industrial or transportation sectors, facilitating the integration of renewable energies and energy storage systems, and the supply of loads. However, new solutions are needed in the modelling, design, power converters, stability, control and operation of MVDC grids to address their challenges, and promote their development and application.
This Special Issue is aiming to present the recent advances, challenges and opportunities related to MVDC grids, and includes, but is not limited to, the following topics:

  • Modelling and simulation techniques for MVDC grids
  • Design of MVDC grids
  • MVDC grids with renewable energy and energy storage systems
  • AC/DC and DC/DC power converters for MVDC grids
  • Control techniques and energy management systems for power converters and MVDC grids
  • Stability of power converters and MVDC grids
  • Normal operation of MVDC grids
  • Fault detection and reconfiguration/restoration of MVDC grids
  • Power quality of MVDC grids
  • State-of-the-art reviews on MVDC grids

Prof. Dr. Luis M. Fernández-Ramírez
Prof. Dr. Francisco Jurado
Prof. Dr. Luis Sainz-Sapera
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • MVDC grid modelling
  • MVDC grid design
  • MVDC smart grids/microgrids
  • Power converters for MVDC grids
  • MVDC grid control/energy management systems
  • MVDC grid operation
  • MVDC grid stability
  • MVDC grid power quality

Published Papers (5 papers)

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Research

14 pages, 6410 KiB  
Article
Upgrading the Power Capacity of a Three-Conductor MVAC Line by Converting to DC
Energies 2022, 15(3), 1080; https://doi.org/10.3390/en15031080 - 01 Feb 2022
Cited by 2 | Viewed by 1682
Abstract
Several countries around the world are undergoing a radical transformation of their electricity networks, with the widespread integration of distributed generation based on renewable energy sources at the center of the change. Under these scenarios, DC links are becoming an attractive option for [...] Read more.
Several countries around the world are undergoing a radical transformation of their electricity networks, with the widespread integration of distributed generation based on renewable energy sources at the center of the change. Under these scenarios, DC links are becoming an attractive option for the infrastructure of modern networks, especially at medium voltage levels. This work is devoted to the integration of DC systems in existing AC networks by converting AC power lines to DC. The work presents a novel method for converting a three-conductor medium voltage AC transmission line to DC. The efficiency of the proposed conversion is assessed in terms of increased power capacity. It is shown that the proposed approach allows for increasing the power capacity of the line by at least 10%. The feasibility and effectiveness of the proposed method are then confirmed by laboratory experiments. Full article
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17 pages, 4878 KiB  
Article
Coordinated Control of Diesel Generators and Batteries in DC Hybrid Electric Shipboard Power System
Energies 2021, 14(19), 6246; https://doi.org/10.3390/en14196246 - 01 Oct 2021
Cited by 9 | Viewed by 3005
Abstract
Hybrid electric ships powered by diesel generators and batteries are the main configuration for shipboard microgrids (SMGs) in the current maritime industry. Extensive studies have been conducted for the hybrid operation mode, whereas the all-electric operation mode and the switching between the aforementioned [...] Read more.
Hybrid electric ships powered by diesel generators and batteries are the main configuration for shipboard microgrids (SMGs) in the current maritime industry. Extensive studies have been conducted for the hybrid operation mode, whereas the all-electric operation mode and the switching between the aforementioned two modes in a system with multiple generators and batteries have not been tested. In this paper, a coordinated approach for a hybrid electric ship is proposed, where two operation modes have been simultaneously considered. More specifically, for achieving an efficient operation with reduced generator wear losses, the governor-less diesel-engine-driven generators have been adopted in the study. According to the practical operation conditions, two operation modes, the all-electric and hybrid modes, are preset. Based on these, the coordination of the generators acting as the main power sources and batteries regulating the power flow and improving the generator efficiency is studied. The governor-less diesel generators are regulated to inject the rated power in order to maximize the generator efficiency, while the DC bus voltage is regulated by DC/DC converters. For the benefit of the overall lifespan of battery banks, power sharing during charging and discharging states have been realized by the state of charge (SoC)-based adaptive droop regulator. For the test of two operation modes, as well as the mode switching, a simulation assessment in a 1 kV DC SMG has been conducted. The simulation results show that the DC bus voltage can be controlled well, and that the power sharing among batteries follows the design. Additionally, smooth transients can be observed during mode switching when the proposed control scheme is applied. Full article
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15 pages, 12580 KiB  
Article
State-Space Model of Quasi-Z-Source Inverter-PV Systems for Transient Dynamics Studies and Network Stability Assessment
Energies 2021, 14(14), 4150; https://doi.org/10.3390/en14144150 - 09 Jul 2021
Cited by 8 | Viewed by 1509
Abstract
Photovoltaic (PV) power systems are increasingly being used as renewable power generation sources. Quasi-Z-source inverters (qZSI) are a recent, high-potential technology that can be used to integrate PV power systems into AC networks. Simultaneously, concerns regarding the stability of PV power systems are [...] Read more.
Photovoltaic (PV) power systems are increasingly being used as renewable power generation sources. Quasi-Z-source inverters (qZSI) are a recent, high-potential technology that can be used to integrate PV power systems into AC networks. Simultaneously, concerns regarding the stability of PV power systems are increasing. Converters reduce the damping of grid-connected converter systems, leading to instability. Several studies have analyzed the stability and dynamics of qZSI, although the characterization of qZSI-PV system dynamics in order to study transient interactions and stability has not yet been properly completed. This paper contributes a small-signal, state-space-averaged model of qZSI-PV systems in order to study these issues. The model is also applied to investigate the stability of PV power systems by analyzing the influence of system parameters. Moreover, solutions to mitigate the instabilities are proposed and the stability is verified using PSCAD time domain simulations. Full article
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23 pages, 10464 KiB  
Article
Demonstration Study of Voltage Control of DC Grid Using Energy Management System Based DC Applications
Energies 2020, 13(17), 4551; https://doi.org/10.3390/en13174551 - 02 Sep 2020
Cited by 1 | Viewed by 1841
Abstract
This paper is about the development of the real-time direct current (DC) network analysis applications for the operation of DC power systems. The applications are located in the central energy management system (EMS) and provide the operator with the optimal solution for operation [...] Read more.
This paper is about the development of the real-time direct current (DC) network analysis applications for the operation of DC power systems. The applications are located in the central energy management system (EMS) and provide the operator with the optimal solution for operation in real time. Developed DC applications are not limited by voltage level. Applications can be used at all DC voltage levels such as low voltage, medium voltage and high voltage. A program configuration and sequence for analyzing the DC distribution system are suggested. Algorithms of each program are presented and the differences when compared with the processes of the applications of the existing alternating current (AC) systems are analyzed. The DC grid demonstration site at the Korea Electric Power Corporation (KEPCO) power testing center is introduced. The details of EMS and applications installation are described. The developed DC applications were installed in the EMS of the demonstration site and verification tests have been carried out. The configuration of the test scenario for testing the voltage control of the DC network is described. The voltage control result is analyzed and the measured data and the results of the applications are verified for compatibility by comparing them with the results of an off-line simulation tool. Finally, the future direction of the development of technology for the operation of the DC grid is introduced. Full article
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18 pages, 10164 KiB  
Article
A Sliding-Mode-Based Duty Ratio Controller for Multiple Parallelly-Connected DC–DC Converters with Constant Power Loads on MVDC Shipboard Power Systems
Energies 2020, 13(15), 3888; https://doi.org/10.3390/en13153888 - 30 Jul 2020
Cited by 4 | Viewed by 1612
Abstract
The development of powered electronic technology has made many aware of the design and control of ship power systems (SPSs), and has made medium voltage DC (MVDC) architecture the main research direction in the future. The negative impedance characteristic of constant power load [...] Read more.
The development of powered electronic technology has made many aware of the design and control of ship power systems (SPSs), and has made medium voltage DC (MVDC) architecture the main research direction in the future. The negative impedance characteristic of constant power load (CPL) generated by the coupling of powered electronic converters will seriously affect the stability of the systems if these converters are not properly controlled. The conventional linear control method can only guarantee the small-signal stability of the system near its equilibrium point. When the operating point changes in a large range, linear control methods will be ineffective. More importantly, research for the large-signal stability of the multi-converter system with CPLs is still rarely involved. In this paper, a sliding-mode-based duty ratio controller (SMDC) is proposed for voltage regulation and current sharing of the multiple parallelly-connected DC–DC converters system loaded by CPLs. By controlling the output voltage of each converter with SMDC, large-signal stability of the coupled bus voltage is ensured. Meanwhile, proportional current sharing between the parallel converters is achieved by droop control integrated in the reference value of converter voltage. Simulation studies were conducted in MATLAB/Simulink, where two typical operating conditions, including the variation of load power and bus voltage, were designed to verify the effectiveness of the proposed method. Moreover, a traditional PID controller was used as a comparison to reflect the superiority of the former. Simulation results showed that the proposed method is able to guarantee large-signal stability of the system in the presence of large-scale variations in load power and bus voltage. The output current of the parallel converters can also be distributed in desired proportions according to the droop coefficient. Full article
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