DOCSLIB.ORG

The Influence of HVDC Transmission on AC Networks

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Influence of HVDC Transmission on AC Networks TRANSMISSION AND DISTRIBUTION The infl uence of HVDC transmission on AC networks Information from Cigré The use of HVDC links between regions within an AC network is becoming increasing important because of the growing challenge of network development. The lack of public acceptance of new overhead lines delays the process. Therefore, more and more underground connections are considered inside AC networks to replace traditional overhead lines, operating in parallel with existing AC lines. The first commercial high voltage direct most effective utilisation of these assets HVDC submarine cable started operation in current ( HVDC) installations date back to in transmission networks. The notion of 1954. This system used mercury arc valves, the 1950s. Nowadays, HVDC technologies "embedded HVDC systems" is defined for which required constant maintenance and are in widespread use worldwide and the purpose of this article as follows: rebuilding. With the development of high have long operational experience. ln fact, "An embedded HVDC system is a DC link voltage and high power thyristors in the early this technology exhibits characteristics with at least two ends being physically 1970s, thyristor valves gradually replaced that have already made it attractive connected within a single synchronous AC the mercury arc valves. Thyristor valves over HVAC transmission for specific network. With such a connection, it can increased system reliability significantly applications, such as very long distance perform not only the basic function of bulk with reduced maintenance. This resulted power, transmission, long submarine cable power transmission, but also, importantly, in fast development of the technology and links and interconnection of asynchronous some additional control functions within the building of several new HVDC systems systems, as well as bulk energy transport. the AC network such as power flow worldwide. Today HVDC is a mature, well- The largest and most recent example of control, voltage control, system stability the latter is the installation of a ±800 kV, developed technology. The thyristor-based improvement and the mitigation of system 7200 MW HVDC link in China. HVDC system uses line-commutated cascading failure." converters, because the thyristors cannot Converting an existing AC line to HVDC An illustration of what is regarded as an be switched off by control action. They operation can increase its own transfer embedded HVDC is given in Fig. 1. switch off naturally at current zero crossing, capacity and, in addition, may increase when the current flowing from the anode the reliability-limited loading of parallel or HVDC transmission: state of the art and to the cathode becomes negative. The contiguous lines remaining in AC service. projects description converters are designed to transfer large HVDC systems perform differently to AC amounts of power for long distances, for connections during steady state, dynamic HVDC transmission can provide interesting sea crossings where AC cables cannot and transient conditions. Compared to AC control functions for the surrounding AC be used because of the large capacitive links, embedded HVDC links offer specific network in which they are embedded, functions that can be seen as advantages such as optimal power flow control, current. The thyristor-based HVDC system but with additional costs, complexity and voltage control, system transient stability is economical beyond a break-even sometimes noticeable drawbacks. improvement, low frequency power distance (a few hundreds of kilometers oscillation damping, prevention of system transmission lines). This article deals with the coordination cascading failure, etc. between HVDC links and AC lines in The typical application of this system parallel with an objective to enhance HVDC energy transmission was developed is interconnection between two points. the understanding in the industry for the in the late 1930s and the first commercial The tapping of an HVDC line is difficult with thyristor-based converters. Another application is the back-to-back HVDC, which provides asynchronous interconnection between two AC systems without transmission line. The asynchronous interconnection permits the regulation of power transfer, blocks cascading failures and prevents the increase of short circuit current. The classical HVDC system is based on a well-established and mature technology. The energy availability of most systems (including the transformer, auxiliary system, cooling) is very high, and may be slightly improved with dedicated equipments The recent development of high power Insulated Gate Bipolar Transistors (IGBT) has caused revolutionary changes in HVDC technology and has made the voltage source converter based DC transmission system possible. The first system has been built in 1997. Today, other manufacturers also offer this technology Fig. 1: Examples of different concepts related to embedded HVDC systems and several systems are successfully in and HVDC systems connecting two asynchronous systems. operation. energize - Jan/Feb 2014 - Page 38 TRANSMISSION AND DISTRIBUTION connecting large AC capacitive filters at the converter stations. For a common LCC- HVDC link, the large filters not only increase the costs, but also occupy large amounts of space of the converter stations. Besides, they also contribute to the temporary overvoltage (TOV) and low-order harmonic resonance problems of the HVDC link when connected to a weak AC system. Another well-known problem of the LCC-HVDC system is the occurrence of commutation failures (especially on the inverter side) caused by disturbances in the AC system. Either depressed voltage magnitude or phase-angle shift of the alternating voltage may reduce the extinction volt-time area of the inverter Fig. 2: Graetz bridge circuit. valve. If the extinction angle of the inverter valve is smaller than 5 to 6°, the previously conducted valve will re-conduct, which will end up with a commutation failure. Commutation failures are common phenomena of LCC-HVDC systems. A single commutation failure generally does no harm to either the converter valves or the AC system. However, a number of repeated commutation failures may force the HVDC link to trip. While the above two problems can be mitigated by relatively easy measures, the third problem is more fundamental, and can become a limiting factor for LCC-HVDC applications. For LCCs, the successful commutation of the alternating current from one valve to the next relies on the stiffness of the alternating voltage, i.e., the network strength of the AC system. If the AC system has low short-circuit capacity relative to the power rating of the HVDC link, problematic interactions Fig. 3: 3-level neutral-point-clamped (NPC) voltage-source converter. between the AC and the DC systems are to be expected. Besides, the SCR of the AC system also imposes an upper limitation on the HVDC power transmission, which HVDC transmission using line-commutated less than 90 degrees, the direct current is is often described by the well-known current-source converters flowing from the positive terminal of the DC maximum power curve (MPC). The major problem with mercury-arc circuit, thus the power is flowing from the As mentioned before, an LCC-HVDC technology, used in the past, was arc AC side to the DC side; if the firing angle is link normally requires reactive-power back failure which destroyed the rectifying greater than 90 degrees, the direct voltage compensation by connecting large AC property of the converter valve and changes polarity, thus the direct current is filters at the converter stations. These consequently triggered other problems. In flowing from the negative terminal of the create additional problems in weak AC the late 1960s, thyristor valve technology DC circuit. The power is then flowing from systems as described below. One such was developed which overcame the the DC side to the AC side. An HVDC link problem is the aforementioned TOV issue. problems of mercury-arc technology. is essentially constructed by two Graetz In case of a sudden change in the active Converters based on either mercury bridges, which are interconnected on the power, or the blocking of the converter, valves or thyristor valves are called line- DC sides. The interconnection could be an the large capacitors at the converter commutated converters (LCC). The basic overhead line, a cable, or a back-to-back station together with the high inductance module of an LCC is the three-phase full- connection. of the AC system cause a temporary wave bridge circuit shown in Fig. 2. This The application of LCC-HVDC technology overvoltage before the protection system topology is known as the Graetz bridge. has been very successful and the disconnects the capacitors. TOVs can Although there are several alternative installations of LCC-HVDC links are also lead to saturation of the converter configurations possible, the Graetz bridge expected to grow at least in the near transformer or transformers close to the DC has been universally used for LCC-HVDC future. However, the LCC technology station. Another problem related to weak- converters as it provides better utilisation suffers from several inherent weaknesses. AC-system connections is the low-order of the converter transformer and a One problem is that the LCC always harmonic resonance. The high inductance lower voltage across the valve when not consumes reactive power, either in rectifier of the AC system and the large filters of the conducting. mode or in inverter mode. Depending HVDC link create a resonance of which the The Graetz bridge can be used for on the firing angles, the reactive power frequency tends to be lower for weak AC transmitting power in two directions, i.e., consumption of an LCC-HVDC converter systems. Generally speaking, the lower the the rectifier mode and the inverter mode. station is approximately 50 to 60% of resonance frequency, the greater the risk This is achieved by applying different firing the active power. The reactive-power for harmful interaction with the converter angles on the valves. If the firing angle is consumption requires compensation by control system.
Load more

Recommended publications
  • A Cascaded DC-AC-AC Grid-Tied Converter for PV Plants with AC-Link
    electronics Article A Cascaded DC-AC-AC Grid-Tied Converter for PV Plants with AC-Link Manuel A. Barrios 1,2,* ,Víctor Cárdenas 1 , Jose M. Sandoval 1, Josep M. Guerrero 2,* and Juan C. Vasquez 2 1 Engineering Department, Autonomous University of San Luis Potosi, Dr. Manuel Nava No. 8, Col. Zona Universitaria Poniente, San Luis Potosí 78290, Mexico; [email protected] (V.C.); [email protected] (J.M.S.) 2 Center for Research on Microgrids (CROM), Department of Energy Technology, Aalborg University, 9220 Aalborg, Denmark; [email protected] * Correspondence: [email protected] (M.A.B.); [email protected] (J.M.G.) Abstract: Cascaded multilevel converters based on medium-frequency (MF) AC-links have been proposed as alternatives to the traditional low-voltage inverter, which uses a bulky low-frequency transformer step-up voltage to medium voltage (MV) levels. In this paper, a three-phase cascaded DC-AC-AC converter with AC-link for medium-voltage applications is proposed. Three stages integrate each DC-AC-AC converter (cell): a MF square voltage generator; a MF transformer with four windings; and an AC-AC converter. Then, k DC-AC-AC converters are cascaded to generate the multilevel topology. This converter’s topological structure avoids the per-phase imbalance; this simplifies the control and reduces the problem only to solve the per-cell unbalance. Two sets of simulations were performed to verify the converter’s operation (off-grid and grid-connected modes). Finally, the papers present two reduced preliminary laboratory prototypes, one validating the cascaded configuration and the other validating the three-phase configuration.
    [Show full text]
  • Impact of Converter Interfaced Generation and Load on Grid Performance
    Impact of Converter Interfaced Generation and Load on Grid Performance by Deepak Ramasubramanian A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Approved January 2017 by the Graduate Supervisory Committee: Vijay Vittal, Chair John Undrill Raja Ayyanar Jiangchao Qin ARIZONA STATE UNIVERSITY May 2017 ABSTRACT Alternate sources of energy such as wind, solar photovoltaic and fuel cells are coupled to the power grid with the help of solid state converters. Continued deregulation of the power sector coupled with favorable government incentives has resulted in the rapid growth of renewable energy sources connected to the distribution system at a voltage level of 34.5kV or below. Of late, many utilities are also investing in these alternate sources of energy with the point of interconnection with the power grid being at the transmission level. These converter interfaced generation along with their associated control have the ability to provide the advantage of fast control of frequency, voltage, active, and reactive power. However, their ability to provide stability in a large system is yet to be investigated in detail. This is the primary objective of this research. In the future, along with an increase in the percentage of converter interfaced renewable energy sources connected to the transmission network, there exists a possi- bility of even connecting synchronous machines to the grid through converters. Thus, all sources of energy can be expected to be coupled to the grid through converters. The control and operation of such a grid will be unlike anything that has been en- countered till now.
    [Show full text]
  • Installation and Operating Instructions for Trained Personnel, Certified by Woodward
    Installation and operating instructions for trained personnel, certified by Woodward (Exemplary illustration) - MP1 Frequency converter system Document no.: 9943-1707 Revision: B EN GB Original operation manual This document is updated regularly. ► Always use the current version of the document. You can find the current version of the document on the Woodward website: www.woodward.com/publications Document history Woodward document revisions • The first released version of a document has the revision acronym New. • All further revisions are identified alphabetically from A to Z. • After the revision Z, AA, AB, AC etc. follows. General corrections Date Version Modification carried out by 16.10.15 A Update document C. Aan de Brugh 16.10.15 B Update document C. Aan de Brugh Product specific corrections Date Version Modification carried out by Table of contents Table of contents 1 Safety .................................................................................................. 6 1.1 Classification of the warning notices with relation to actions ..................................... 6 1.2 Intended use ...................................................................................................................... 6 1.3 General safety instructions .............................................................................................. 7 1.3.1 Danger of electrocution ....................................................................................................... 7 1.3.2 Material damage by electrostatic discharge .......................................................................
    [Show full text]
  • Power Converter Circuits for Voltage Boosting, Balancing and Reliable Operation of Energy Systems
    POWER CONVERTER CIRCUITS FOR VOLTAGE BOOSTING, BALANCING AND RELIABLE OPERATION OF ENERGY SYSTEMS By Wei Qian A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY ELECTRICAL ENGINEERING 2011 ABSTRACT POWER CONVERTER CIRCUITS FOR VOLTAGE BOOSTING, BALANCING AND RELIABLE OPERATION OF ENERGY SYSTEMS By Wei Qian Hybrid electric vehicle (HEV) and alternative energy have received growing attention nowadays, due to their contribution to the sustainable development. In these systems, power electronic circuits play a key role in bridging over the differences between sources and loads. The thesis investigates power converters to interface the energy sources and to prolong the life of the critical energy storage devices. The boost converter in commercial HEV powertrains meets obstacles to upgrading the rating while downsizing the converter. A four-level dc-dc converter, and its special case―a 3X dc-dc converter that operates at three discrete voltage ratios, can overcome the drawbacks by dramatically reducing the inductance requirement. The operating principles, the current ripple, the power loss analysis and a clamping circuit are introduced. The concept is verified by the experimental results from two 30-kW and 55-kW prototypes. Yet, for other applications like FC, PV and TEG, it is beyond the ability of the 3X dc-dc converter to attain high boost gain. Thus, a new switched-capacitor dc-dc converter is proposed. The component cost comparison and the power loss analysis demonstrate its many features such as low component power rating and count, low capacitance requirement, light weight and high efficiency.
    [Show full text]
  • A Report on the Environmental Impact of Clean Path NY's High-Voltage
    An Unjust Transition: A Report on the Environmental Impact of Clean Path NY’s High-Voltage Infrastructure in the South Bronx July 2021 Table of Contents INTRODUCTION: 2 CLEAN PATH PROPOSAL: BRIEF DESCRIPTION 4 CLEAN PATH AND THE SOUTH BRONX 6 HIGH VOLTAGE AC TRANSMISSION 7 STUDY AREA POTENTIAL LOCATION 8 STUDY AREA OF ANALYSIS 8 NEIGHBORHOOD CONTEXT NEAR POSSIBLE CONVERTER STATION LOCATION 10 PROPOSED AND CONSTRUCTED HOUSING BUILDINGS IN STUDY AREA 13 DEMOGRAPHICS 14 ENVIRONMENTAL IMPACT AND HUMAN EFFECTS: 14 CONCLUSION 15 1 | Page Introduction: Both the Biden Administration and state governments across the U.S. are making a concerted push to reduce Greenhouse Gas (GHG) emissions. Increased hurricane activity and earlier hurricane seasons, along with longer and extreme heat waves are examples of the effects of climate change and the critical importance of reducing the production of greenhouse gases. President Biden has pledged “a federal investment of $1.7 trillion over the next three years” to bring about a “Clean Energy Revolution” informed by the principles of “Environmental Justice” (Biden and Harris Campaign Website, 2020). With more electric vehicles being introduced, more e-cycles on the streets of major cities, and a renewed emphasis on connecting renewable energy to the existing electrical grid, there is a pressing need for more energy, cleaner sources, and new infrastructure to address this transition. This transition to a low-carbon future is urgent work that will require intense focus from policymakers, binding GHG reduction commitments throughout the economy, and both public and private investment in clean energy generation and transmission. While we all gain by taking swift action to address climate change, how these new clean energy assets are developed and deployed will determine which communities reap the benefits of this transition and which will bear the principal burdens.
    [Show full text]
  • Wide-Range Operation of High Step-Up DC-DC Converters with Multimode Rectifiers
    electronics Article Wide-Range Operation of High Step-Up DC-DC Converters with Multimode Rectifiers Andrii Chub 1 , Dmitri Vinnikov 1,2,* , Oleksandr Korkh 1, Tanel Jalakas 1 and Galina Demidova 2 1 Power Electronics Group, Department of Electrical Power Engineering and Mechatronics, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia; [email protected] (A.C.); [email protected] (O.K.); [email protected] (T.J.) 2 Faculty of Control System and Robotics, ITMO University, 197101 St. Petersburg, Russia; [email protected] * Correspondence: [email protected]; Tel.: +372-620-3705 Abstract: This paper discusses the essence and application specifics of the multimode rectifiers in high step-up DC-DC converters. It presents an overview of existing multimode rectifiers. Their use enables operation in the wide input voltage range needed in highly demanding applications. Owing to the rectifier mode changes, the converter duty cycle can be restricted to a range with a favorable efficiency. It is shown that the performance of such converters depends on the front-end inverter type. The study considers current- and impedance-source front-end topologies, as they are the most relevant in high step-up applications. It is explained why the full- and half-bridge implementations provide essentially different performances. Unlike the half-bridge, the full-bridge implementation shows step changes in efficiency during the rectifier mode changes, which could compromise the long-term reliability of the converter. The theoretical predictions are corroborated by experimental examples to compare performance with different boost front-end inverters. Citation: Chub, A.; Vinnikov, D.; Keywords: DC-DC converters; high step-up converters; wide input range; multimode rectifier Korkh, O.; Jalakas, T.; Demidova, G.
    [Show full text]
  • Cascaded Converters for Integration and Management of Grid Level Energy Storage Systems Zuhair Muhammed Alaas Wayne State University
    Wayne State University Wayne State University Dissertations 1-1-2017 Cascaded Converters For Integration And Management Of Grid Level Energy Storage Systems Zuhair Muhammed Alaas Wayne State University, Follow this and additional works at: http://digitalcommons.wayne.edu/oa_dissertations Part of the Electrical and Computer Engineering Commons Recommended Citation Alaas, Zuhair Muhammed, "Cascaded Converters For Integration And Management Of Grid Level Energy Storage Systems" (2017). Wayne State University Dissertations. 1772. http://digitalcommons.wayne.edu/oa_dissertations/1772 This Open Access Dissertation is brought to you for free and open access by DigitalCommons@WayneState. It has been accepted for inclusion in Wayne State University Dissertations by an authorized administrator of DigitalCommons@WayneState. CASCADED CONVERTERS FOR INTEGRATION AND MANAGEMENT OF GRID LEVEL ENERGY STORAGE SYSTEMS by ZUHAIR ALAAS DISSERTATION Submitted to the Graduate School of Wayne State University, Detroit, Michigan in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY 2017 MAJOR: ELECTRICAL ENGINEERING Approved By: ______________________________________ Advisor Date ______________________________________ ______________________________________ ______________________________________ © COPYRIGHT BY ZUHAIR ALAAS 2017 All Rights Reserved DEDICATION I dedicate my research work to Alaas family. A special feeling of completion of PhD degree to my dad and mom. Their words of support and encouragement still ring in my ears. Great thanks for my sisters, brothers and all Alaas family members who have never left my side. Also, many thanks to my uncles Zuhair, Abdullah and Ali. I will always appreciate all they have done. Finally, I dedicate this dissertation and give special thanks to my wonderful wife and my kids for being with me throughout the entire PhD program.
    [Show full text]
  • Full-Scale Medium-Voltage Converters for Wind Power Generators up to 7 MVA 1 Introduction
    Full-Scale Medium-Voltage Converters for Wind Power Generators up to 7 MVA Philippe Maibach, Alexander Faulstich, Markus Eichler, Stephen Dewar ABB Switzerland Ltd CH-5300 Turgi, Switzerland Phone: +41 58 58 9 32 35 Fax: +41 58 58 9 26 18 E-mail: [email protected] [email protected] [email protected] [email protected] URL: www.abb.com „Abstract“ The ongoing increase in the share of wind power in installed generation capacity continuously increasing number of wind power plants brought into operation forces the transmission system operators (TSO) to tighten their grid connection rules in order to limit the effects on network quality. These new rules demand that wind power plants and farms support the electricity network throughout their operation. Wind turbines using full-scale converters include several advantages and are most suitable to be adapted flexibly to different grid requirements without the need for additional reactive power compensation equipment. With larger turbine unit sizes, medium-voltage converter systems are suitable for the corresponding high power. Based on platforms widely used for industrial drives applications, ABB has successfully applied reliable medium-voltage converter technology to wind power. Keywords: “IGCT”, “Permanent magnet generator”, “Wind generator systems”, “Voltage Source Inverters”, “Grid code” 1 Introduction In the early days of the wind power industry, wind turbine manufacturers developed lower power wind turbines, which were installed as single units or in small groups at a given location. Increasingly higher power turbines are installed and grouped into large farms or wind power stations. The turbine manufacturers are faced with a number of challenges such as larger and heavier mechanical structures, more severe safety issues, environmental compatibility issues, handling high electrical power within the nacelle and tower, and last but not least the set-up of wind parks and connecting them to the distribution or transmission grid.
    [Show full text]
  • Application Guide Eaton Xiria
    Xiria 3.6-24 kV Medium Voltage Ring Main Unit Application Guide Xiria Powering business worldwide Eaton delivers the power inside hundreds of products that are answering the demands of today’s fast changing world. We help our customers worldwide manage the power they need for buildings, aircraft, trucks, cars, machinery and entire businesses. And we do it in a way that consumes fewer resources. Next generation Powering Greener Buildings transportation and Businesses Eaton is driving the Eaton’s Electrical Group is a development of new leading provider of power technologies – from hybrid quality, distribution and control drive trains and emission solutions that increase energy control systems to advanced efficiency and improve power engine components – that quality, safety and reliability. reduce fuel consumption and Our solutions offer a growing emissions in trucks and cars. portfolio of “green” products and services, such as energy Higher expectations audits and real-time energy consumption monitoring. We continue to expand our Eaton’s Uninterruptible Power aerospace solutions and Supplies (UPS), variable services to meet the needs of speed drives and lighting new aviation platforms, controls help conserve energy including the high-flying light and increase efficiency. jet and very light jet markets. Building on our strengths Our hydraulics business combines localised service and support with an innovative portfolio of fluid power solutions to answer the needs of global infrastructure projects, including locks, canals and dams. MV Switchgear Technology is in our DNA Eaton’s knowledge and understanding of industries, applications, technology and products enables us to offer customers safe, reliable and high performance solutions.
    [Show full text]
  • Interface Converters for Residential Battery Energy Storage Systems: Practices, Difficulties and Prospects
    energies Article Interface Converters for Residential Battery Energy Storage Systems: Practices, Difficulties and Prospects Ilya A. Galkin 1,* , Andrei Blinov 2 , Maxim Vorobyov 1 , Alexander Bubovich 1 , Rodions Saltanovs 1 and Dimosthenis Peftitsis 3 1 Faculty of Electrical and Environmental Engineering, Riga Technical University, LV1048 Riga, Latvia; [email protected] (M.V.); [email protected] (A.B.); [email protected] (R.S.) 2 Department of Electrical Power Engineering and Mechatronics, Tallinn University of Technology, 19086 Tallinn, Estonia; [email protected] 3 Department of Electrical Power Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; [email protected] * Correspondence: [email protected] Abstract: Recent trends in building energy systems such as local renewable energy generation have created a distinct demand for energy storage systems to reduce the influence and dependency on the electric power grid. Under the current market conditions, a range of commercially available residential energy storage systems with batteries has been produced. This paper addresses the area of energy storage systems from multiple directions to provide a broader view on the state- of-the-art developments and trends in the field. Present standards and associated limitations of storage implementation are briefly described, followed by the analysis of parameters and features of commercial battery systems for residential applications. Further, the power electronic converters are reviewed in detail, with the focus on existing and perspective non-isolated solutions. The analysis Citation: Galkin, I.A.; Blinov, A.; covers well-known standard topologies, including buck-boost and bridge, as well as emerging Vorobyov, M.; Bubovich, A.; Saltanovs, R.; Peftitsis, D.
    [Show full text]
  • Solid State Transformers Topologies, Controllers, and Applications: State-Of-The-Art Literature Review
    electronics Review Solid State Transformers Topologies, Controllers, and Applications: State-of-the-Art Literature Review Ahmed Abu-Siada 1,* , Jad Budiri 1 and Ahmed F. Abdou 2 1 Department of Electrical and Computer Engineering, Curtin University, Bentley, WA6102, Australia; [email protected] 2 School of Engineering and Information Technology, University of New South Wales, Canberra, BC 2610 Australia; [email protected] * Correspondence: [email protected]; Tel.: +61-(8)-9266-7287 Received: 16 October 2018; Accepted: 1 November 2018; Published: 5 November 2018 Abstract: With the global trend to produce clean electrical energy, the penetration of renewable energy sources in existing electricity infrastructure is expected to increase significantly within the next few years. The solid state transformer (SST) is expected to play an essential role in future smart grid topologies. Unlike traditional magnetic transformer, SST is flexible enough to be of modular construction, enabling bi-directional power flow and can be employed for AC and DC grids. Moreover, SSTs can control the voltage level and modulate both active and reactive power at the point of common coupling without the need to external flexible AC transmission system device as per the current practice in conventional electricity grids. The rapid advancement in power semiconductors switching speed and power handling capacity will soon allow for the commercialisation of grid-rated SSTs. This paper is aimed at introducing a state-of-the-art review for SST proposed topologies, controllers, and applications. Additionally, strengths, weaknesses, opportunities, and threats (SWOT) analysis along with a brief review of market drivers for prospective commercialisation are elaborated.
    [Show full text]
  • Electromagnetic and Thermal Design of a Multilevel Converter with High Power Density and Reliability
    Liudmila Smirnova ELECTROMAGNETIC AND THERMAL DESIGN OF A MULTILEVEL CONVERTER WITH HIGH POWER DENSITY AND RELIABILITY Thesis for the degree of Doctor of Science (Technology) to be presented with due permission for public examination and criticism in the Auditorium 1382 at Lappeenranta University of Technology, Lappeenranta, Finland on the 13th of August, 2015, at noon. Acta Universitatis Lappeenrantaensis 651 Supervisors Professor Juha Pyrhönen Electrical Engineering LUT School of Energy Systems Lappeenranta University of Technology Finland Professor Pertti Silventoinen Electrical Engineering LUT School of Energy Systems Lappeenranta University of Technology Finland Professor Olli Pyrhönen Electrical Engineering LUT School of Energy Systems Lappeenranta University of Technology Finland Reviewers Associate Professor Michal Frivaldský Department of Mechatronics and Electronics Faculty of Electrical Engineering University of Žilina Slovakia Dr. Veli-Matti Leppänen ABB Oy Finland Opponent Associate Professor Michal Frivaldský Department of Mechatronics and Electronics Faculty of Electrical Engineering University of Žilina Slovakia Dr. Veli-Matti Leppänen ABB Oy Finland ISBN 978-952-265-828-9 ISBN 978-952-265-829-6 (PDF) ISSN-L 1456-4491 ISSN 1456-4491 Lappeenrannan teknillinen yliopisto Yliopistopaino 2015 Abstract Liudmila Smirnova Lappeenranta 2015 127 pages Acta Universitatis Lappeenrantaensis 651 Diss. Lappeenranta University of Technology ISBN 978-952-265-828-9, ISBN 978-952-265-829-6 (PDF), ISSN-L 1456-4491, ISSN 1456-4491 Electric energy demand has been growing constantly as the global population increases. To avoid electric energy shortage, renewable energy sources and energy conservation are emphasized all over the world. The role of power electronics in energy saving and development of renewable energy systems is significant.
    [Show full text]