Journal articles: 'Solid-state transformer (SST)'

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Khan, Saniya, Khaliqur Rahman, Mohd Tariq, Salman Hameed, Basem Alamri, and Thanikanti Sudhakar Babu. "Solid-State Transformers: Fundamentals, Topologies, Applications, and Future Challenges." Sustainability 14, no. 1 (December 29, 2021): 319. http://dx.doi.org/10.3390/su14010319.

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Solid-state transformers (SSTs) have emerged as a superior alternative to conventional transformers and are regarded as the building block of the future smart grid. They incorporate power electronics circuitry and high-frequency operation, which allows high controllability and enables bi-directional power flow, overcoming the limitations of conventional transformers. This paper presents a detailed analysis of the solid-state transformer, expounding the fundamentals, converter topologies, applications, and future challenges of the SST in a systematic manner. The paper discusses the necessity of improved replacement of the low-frequency transformers (LFTs) and presents the configuration of SST. It presents SST fundamentals in individual stages and explores its origin and evolution. The basic topologies, their specifications, and control strategies are also described. The applications of SST as a replacement of LFTs are discussed along with recent applications. The future challenges for real-time implementation of SSTs are explored, and research directions are proposed.

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Liu, Yang, Da Hai Zhang, and De Da Sun. "Performance Analysis of a Solid State Transformer for Smart Grid." Applied Mechanics and Materials 441 (December 2013): 174–77. http://dx.doi.org/10.4028/www.scientific.net/amm.441.174.

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Solid State Transformer (SST) has many attractive characteristics, including power quality improvement and reactive power compensation. The paper investigates the topology and control schemes of SST, and discusses its flexibility and reliability for both grid and customers. A model of SST applied for distribution network is constructed, and simulation shows the SST with appropriate control scheme can provide excellent power supply during both steady-state and dynamic-state with varying load.

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Umar, Bashir Musa, Yusuf Jibril, Boyi Jimoh, Abdullahi Bala Kunya, Yusuf Abubakar Maiwada, Safiya Aliyu, and Musa Mohammed. "Glance into solid-state transformer technology: a mirror for possible research areas." Journal of Applied Materials and Technology 2, no. 1 (October 10, 2020): 1–13. http://dx.doi.org/10.31258/jamt.2.1.1-13.

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Solid-State Transformer (SST), a power electronics based transformer is an emerging technology in electric power system. The transformer is being investigated to completely replace existing Line/Low Frequency Transformer (LFT). SST is composed of either of the two topologies: AC-DC-AC, two steps approach; or AC-AC, single-step approach. The two steps approach consists of three stages: AC-DC; DC-DC; and DC-AC stages. The DC-DC stage is made up of a boost DC-DC converter, a DC-AC inverter and a High Frequency Transformer, HFT. Therefore, SST performs the tasks of LFT by means of power electronic converters and HFT. The main essence of SST is to provide solution to the problem of bulkiness and heaviness of the LFT in the power distribution network. This is with the view to providing reduction in construction cost, cost of maintenance and transportation. The power electronics transformer provides numerous advantages which are grouped into: The transformer has high power density; it functions in blackouts and brownouts; and it provides easy means of distributed renewable energy integration into associated grid. Therefore, this paper provides a glance into the technology of the SST for its better understating and promotion of research activities in the area.

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Yun, Chun-gi, and Younghoon Cho. "Active Hybrid Solid State Transformer Based on Multi-Level Converter Using SiC MOSFET." Energies 12, no. 1 (December 26, 2018): 66. http://dx.doi.org/10.3390/en12010066.

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As the types of loads have been diversified and demand has increased, conventional distribution transformers are difficult to maintain the constant voltage against voltage drop along with distance, grid voltage swell/sag, and various loads. Also, it is hard to control the power flow when connecting renewable energy sources. Active hybrid solid state transformer (AHSST) is application to keep the voltage and power quality. AHSST is a system that combines conventional distribution transformer and converter. Accordingly, it can be applied directly to distribution infrastructure and it has both the advantages of solid state transformer (SST) and conventional transformer. AHSST is capable of active voltage and current control and power factor control. It has a simpler structure than SST and it can perform the same performance with the lower rating converter. This paper presents two stage AHSST system based on multi-level converter. The converter is composed of the back-to-back converter using silicon carbide (SiC) metal-oxide semiconductor field effect transistor (MOSFET). Proposed system has a wider voltage and power flow control range, lower filter size, and simpler control sequence than existing AHSST systems. The performance of the proposed system was verified by prototype system experiments.

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Jeong, Dong-Keun, Hyeok-Jin Yun, Si-Ho Park, Myoung-Ho Kim, Myung-Hyo Ryu, Ju-Won Baek, and Ho-Sung Kim. "13.2 kV Class 3-Phase Solid State Transformer System Based on EtherCAT Communication." Electronics 11, no. 19 (September 27, 2022): 3092. http://dx.doi.org/10.3390/electronics11193092.

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This paper presents a 13.2 kV class 3-phase solid-state transformer (SST) based on EtherCAT communication. In general, when the structure of the unit module is determined, the number of high-frequency isolated transformers (HFIT) is also proportional to the number of modules. The structure most considered in SST is a 1:1 combination of AC/DC converter and DC/DC converter. To optimally implement a 3-phase SST, a topology for reducing passive elements such as switching elements and HFIT is proposed. It also describes the design of HFIT used in DC/DC converter. EtherCAT communication with high transmission speed and expandability is applied to control the SST composed of unit modules stably, and a multi-core microcontroller unit (MCU) is applied to achieve both a high-speed communication cycle and complicated control algorithm execution. The discussions are validated using a 300 kW 13.2 kV class 3-phase SST prototype in various conditions.

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Valedsaravi, Seyedamin, Abdelali El Aroudi, and Luis Martínez-Salamero. "Review of Solid-State Transformer Applications on Electric Vehicle DC Ultra-Fast Charging Station." Energies 15, no. 15 (August 2, 2022): 5602. http://dx.doi.org/10.3390/en15155602.

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The emergence of DC fast chargers for electric vehicle batteries (EVBs) has prompted the design of ad-hoc microgrids (MGs), in which the use of a solid-state transformer (SST) instead of a low-frequency service transformer can increase the efficiency and reduce the volume and weight of the MG electrical architecture. Mimicking a conventional gasoline station in terms of service duration and service simultaneity to several customers has led to the notion of ultra-fast chargers, in which the charging time is less than 10 min and the MG power is higher than 350 kW. This survey reviews the state-of-the-art of DC ultra-fast charging stations, SST transformers, and DC ultra-fast charging stations based on SST. Ultra-fast charging definition and its requirements are analyzed, and SST characteristics and applications together with the configuration of power electronic converters in SST-based ultra-fast charging stations are described. A new classification of topologies for DC SST-based ultra-fast charging stations is proposed considering input power, delta/wye connections, number of output ports, and power electronic converters. More than 250 published papers from the recent literature have been reviewed to identify the common understandings, practical implementation challenges, and research opportunities in the application of DC ultra-fast charging in EVs. In particular, the works published over the last three years about SST-based DC ultra-fast charging have been reviewed.

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Abu-Siada, Ahmed, Jad Budiri, and Ahmed Abdou. "Solid State Transformers Topologies, Controllers, and Applications: State-of-the-Art Literature Review." Electronics 7, no. 11 (November 5, 2018): 298. http://dx.doi.org/10.3390/electronics7110298.

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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.

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Li, Zheng, Tao Zheng, Yani Wang, and Chang Yang. "A Hierarchical Coordinative Control Strategy for Solid State Transformer Based DC Microgrids." Applied Sciences 10, no. 19 (September 29, 2020): 6853. http://dx.doi.org/10.3390/app10196853.

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A solid state transformer (SST), as a kind of energy router in the Energy Internet, provides a unified access point for AC or DC distributed power subjects. However, the DC-link capacitors inside the SST will suffer huge voltage fluctuations when the output power of the microgrid changes dramatically. With respect to this problem, caused by the random and intermittent characteristics of distributed generation (DG), a hierarchical coordinative control strategy is proposed. Compared with the common independent control, the proposed method not only makes full use of the regulation capacity of super capacitors, but also enhances the dynamic power tracking speed and reduces the speed difference between different stages of an SST. The dynamic voltage response under the proposed method is analyzed in frequency domain and compared with the independent control. To validate the effectiveness of the coordinative control strategy, a simulation model of an SST-based grid-connected DC microgrid system is established, and the topology of the SST is improved. The voltage stability of the DC bus is compared under different control strategies, and the coordinative control strategy is also verified, effectively under transition conditions.

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Ismail, Abdelrahman, Mahmoud S. Abdel-Majeed, Mohamed Y. Metwly, Ayman S. Abdel-Khalik, Mostafa S. Hamad, Shehab Ahmed, Eman Hamdan, and Noha A. Elmalhy. "Solid-State Transformer-Based DC Power Distribution Network for Shipboard Applications." Applied Sciences 12, no. 4 (February 14, 2022): 2001. http://dx.doi.org/10.3390/app12042001.

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Due to simplicity, efficiency, and the ability to accommodate energy storage devices, DC distribution networks have been seen as an optimal alternative to AC distribution networks, especially aboard future electric ships. The emerging distribution DC system entails new control and management techniques. Therefore, an integrated DC power distribution network aboard an electric ship is selected as the case study in this paper. To meet the requirements of such a large-scale mobile power system, a multiport solid-state transformer (SST) based on silicon carbide (SiC) switches/MOSFETs is proposed. Thus, the system embodiment can significantly be reduced. Moreover, at the DC distribution level, a high penetration of renewable generation with energy storage is allowed and a six-phase asymmetrical induction machine (IM) can directly be integrated. Simulations have been conducted based on a 2 MW shipboard distribution network. The effects of the propulsion system dynamics on the SST are highlighted as well. Finally, a 2 kW lab-scale prototype has been implemented to validate the theoretical findings.

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Oliveira, Tiago, André Mendes, and Luís Caseiro. "Model Predictive Control for Solid State Transformers: Advances and Trends." Energies 15, no. 22 (November 8, 2022): 8349. http://dx.doi.org/10.3390/en15228349.

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Due to its high functionality, the solid state transformer (SST) represents an emerging technology with huge potential to replace the conventional low-frequency transformer (LFT) in a wide range of applications, including railway traction, smart grids, and others. On the other hand, model predictive control (MPC) has proven to be a highly promising control approach for several power electronics systems, especially those based on multiple power converters. Considering these facts, over recent years, different MPC techniques have been proposed for different types of SSTs. In addition to that, numerous MPC strategies have also been investigated for various power converters topologies that can be used in SSTs. However, a paper summarizing and discussing MPC strategies in the framework of SSTs has not yet been proposed in the literature, being the main goal of this work. In this paper, all the existing MPC techniques in complete SST topologies will be presented and discussed. In addition, for the sake of the example, an overview of MPC strategies in converter topologies typically used in SSTs will also be presented.

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Song, Jin-Sol, Ji-Soo Kim, Barry Mather, and Chul-Hwan Kim. "Hosting Capacity Improvement Method Using MV–MV Solid-State-Transformer." Energies 14, no. 3 (January 26, 2021): 622. http://dx.doi.org/10.3390/en14030622.

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As a large number of distributed generations are connected to the distribution system, research on the hosting capacity is actively being conducted. In particular, various methods, such as smart inverter functionality, co-located energy storage systems (ESS), and the use of on-load tap changers (OLTC), have been proposed to improve the hosting capacity. In this paper, a method to improve the hosting capacity by utilizing a solid-state transformer (SST) and its unique control capability is proposed. Lastly, the proposed method is verified in the distribution system of the Republic of Korea using the OpenDSS program.

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Farnesi, Stefano, Mario Marchesoni, Massimiliano Passalacqua, and Luis Vaccaro. "Solid-State Transformers in Locomotives Fed through AC Lines: A Review and Future Developments." Energies 12, no. 24 (December 10, 2019): 4711. http://dx.doi.org/10.3390/en12244711.

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One of the most important innovation expectation in railway electrical equipment is the replacement of the on-board transformer with a high power converter. Since the transformer operates at line-frequency (i.e., 50 Hz or 16 2/3 Hz), it represents a critical component from weight point of view and, moreover, it is characterized by quite poor efficiency. High power converters for this application are characterized by a medium frequency inductive coupling and are commonly referred as Power Electronic Transformers (PET), Medium Frequency Topologies or Solid-State Transformers (SST). Many studies were carried out and various prototypes were realized until now, however, the realization of such a system has some difficulties, mainly related to the high input voltage (i.e., 25 kV for 50 Hz lines and 15 kV for 16 2/3 Hz lines) and the limited performance of available power electronic switches. The aim of this study is to present a survey on the main solutions proposed in the technical literature and, analyzing pros and cons of these studies, to introduce new possible circuit topologies for this application.

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Mollik, Mohammad Sazib, Mahammad A. Hannan, Md Subbir Reza, Muhamad Safwan Abd Rahman, Molla Shahadat Hossain Lipu, Pin Jern Ker, Muhamad Mansor, and Kashem M. Muttaqi. "The Advancement of Solid-State Transformer Technology and Its Operation and Control with Power Grids: A Review." Electronics 11, no. 17 (August 24, 2022): 2648. http://dx.doi.org/10.3390/electronics11172648.

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Solid-state transformer (SST) technology is one of the developing technologies that will be widely used in the future to integrate low-voltage and high-voltage networks with control circuitries and power electronics converters, facilitating renewables integration in smart grid applications. SST technology has crucial key advantageous features, including compact size and weight, low cost, and ease of connection in offshore applications. However, SST technology exhibits a few concerns, such as implementation, protection, economic, and communication compatibility, that need to be addressed. This paper aims to review SST technology with its advanced control schemes and provide future directions for research and development, applications, and prospects. In line with this, highly cited SST technology papers are examined to derive and summarize concerning issues related to its operation and control with further research development of power grids. Moreover, this review discusses the assessment and state-of-the-art technology of SSTs in different applications, focusing on configurations, control circuitry, and their drawbacks and benefits. Numerous issues and challenges of SST technology are explored to identify the existing knowledge gaps and potential future recommendations. All these critical analyses, information, and evaluations would benefit power engineers and researchers in developing and implementing advanced intelligent SST technologies for sustainable energy management in future power systems.

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Fuentes, Carlos, Hector Chavez, and Mario R. Arrieta Paternina. "Predictive Control-Based NADIR-Minimizing Algorithm for Solid-State Transformer." Energies 15, no. 1 (December 23, 2021): 73. http://dx.doi.org/10.3390/en15010073.

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Solid-state transformers (SSTs) are becoming an important solution to control active distribution systems. Their significant flexibility in comparison with traditional magnetic transformers is essential to ensure power quality and protection coordination at the distribution level in scenarios of large penetration of distributed energy resources such as renewables, electric vehicles and energy storage. However, the power electronic interface of SSTs decouples the nature of the inertial and frequency responses of distribution loads, deteriorating the frequency stability, especially under the integration of large-scale solar and wind power plants. Despite the virtual inertia/voltage sensitivity-based algorithms that have been proposed, the frequency sensitivity of loads and the capability of guaranteeing optimal control, considering the operating restrictions, have been overlooked. To counteract this specific issue, this work proposes a predictive control-driven approach to provide SSTs with frequency response actions by a strategy that harnesses the voltage and frequency sensibility of distribution loads and considers the limitations of voltage and frequency given by grid codes at distribution grids. In particular, the control strategy is centered in minimizing the NADIR of frequency transients. Numerical results are attained employing an empirically-validated model of the power system frequency dynamics and a dynamic model of distribution loads. Through proportional frequency control, the results of the proposed algorithm are contrasted. It is demonstrated that the NADIR improved about 0.1 Hz for 30% of SST penetration.

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Roger, Daniel, Ewa Napieralska, Krzysztof Komeza, and Piotr Napieralski. "Design of High-Power Solid-State Transformers with Grain-Oriented Electrical Steel Cores." Electronics 11, no. 15 (July 31, 2022): 2398. http://dx.doi.org/10.3390/electronics11152398.

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The paper proposes a simple structure of high-power solid-state transformers (SSTs) able to control the energy flow in critical lines of the medium-voltage (20 kV) distribution grid. With an increasing number of renewable intermittent sources connected at the nodes of the meshed distribution grid and a reduced number of nodes connected to large power plants, the distribution grid stability is more and more difficult to achieve. Control of the energy flow in critical lines can improve the stability of the distribution grid. This control can be provided by the proposed high-power SSTs operating a 20 kV with powers over 10 MW. This function is difficult to achieve with standard SST technologies that operate at high frequencies. These devices are made with expensive magnetic materials (amorphous or nanocrystalline cores) and a limited power by SST cells. The required total power is reached by assembling many SST cells. On the other hand, existing SST designs are mainly aimed at reducing the equipment’s size and it is difficult to design small objects able to operate at high voltages. The authors propose to use cores made with grain-oriented electrical steel (GOES) thin strips assembled in wound cores. Experimental results obtained, with GOES wound cores, show that the core losses are lower for a square voltage than for a sine one. This counterintuitive result is explained with an analytical calculus of eddy currents and confirmed by a non-linear time-stepping simulation. Therefore, simple converter structures, operating with rectangular voltages and low switching losses, are the best solutions. Experimental results also show that the core losses decrease with temperature. Consequently, high-power SST cells can be made with transformers whose GOES cores are hotter than coils for reducing core losses and keeping copper losses at low levels. The paper proposes an appropriate transformer mechanical structure that avoids any contact between the hot GOES wound core and the winding, with a specific cooling system and thermal insulation of the hot GOES wound core. The proposed design makes it possible to build SST cells over 1MW and full SSTs over 10 MW at moderate costs.

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Ye, Qing, Ran Mo, and Hui Li. "Multiple Resonances Mitigation of Paralleled Inverters in a Solid-State Transformer (SST) Enabled AC Microgrid." IEEE Transactions on Smart Grid 9, no. 5 (September 2018): 4744–54. http://dx.doi.org/10.1109/tsg.2017.2669261.

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La Ganga, Alessandro, Roberto Re, and Paolo Guglielmi. "Input Parallel Output Series Structure of Planar Medium Frequency Transformers for 200 kW Power Converter: Model and Parameters Evaluation." Energies 14, no. 5 (March 7, 2021): 1450. http://dx.doi.org/10.3390/en14051450.

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Nowadays, the demand for high power converters for DC applications, such as renewable sources or ultra-fast chargers for electric vehicles, is constantly growing. Galvanic isolation is mandatory in most of these applications. In this context, the Solid State Transformer (SST) converter plays a fundamental role. The adoption of the Medium Frequency Transformers (MFT) guarantees galvanic isolation in addition to high performance in reduced size. In the present paper, a multi MFT structure is proposed as a solution to improve the power density and the modularity of the system. Starting from 20kW planar transformer model, experimentally validated, a multi-transformer structure is analyzed. After an analytical treatment of the Input Parallel Output Series (IPOS) structure, an equivalent electrical model of a 200kW IPOS (made by 10 MFTs) is introduced. The model is validated by experimental measurements and tests.

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Rehman, Abdur, Malik Imran-Daud, Syed Kamran Haider, Ateeq Ur Rehman, Muhammad Shafiq, and Elsayed Tag Eldin. "Comprehensive Review of Solid State Transformers in the Distribution System: From High Voltage Power Components to the Field Application." Symmetry 14, no. 10 (September 27, 2022): 2027. http://dx.doi.org/10.3390/sym14102027.

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This paper presents a systematical and progressive appraisal of the technology since the inception of AC-AC conversion, which is seen to be an indispensable and vital for the advancement of the Solid State Transformer (SST) in a distribution system. Special attention is given to the concepts/topologies and architecture of the SST, the DC-DC conversion devices in the isolation facet, the inversion gadget in the bridge arrangement and their integration in the development of an economically viable and efficient SST design. For the purpose of this article, a number of research papers, research proposals and research dissertations/studies have been accessed that mostly cover work related to this device and brief discussions about several aspects. The various sections of this article are correspondingly devoted to the review of SST design and its various configurations, the significant stages of the DC-DC converter from a transformer-specific perspective and lastly the high-frequency inverter. In critical appraisal, the SST in a three-stage perspective, the dual half-bridge converter and high-frequency half-bridge inverter are the most viable and promising means, offering tremendous advantages over other configurations with emphasis on economy, high flexibility and control performance; thereby weighed as the most workable, practical and realistic solutions. The foremost potential application of this expedient includes a vital component of the power grid.

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Park, Kiwoo, and Kyo-Beum Lee. "A Bidirectional Double Uneven Power Converter Based DC–DC Converter for Solid-State Transformers." Electronics 7, no. 11 (November 19, 2018): 334. http://dx.doi.org/10.3390/electronics7110334.

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This paper presents a novel bidirectional double uneven power (BiDUP) based dc-dc converter and its design and control methods. The proposed converter utilizes two dual active bridge (DAB) converters with different power ratings in a special way to realize zero current switching (ZCS), where both turn-on and turn-off switchings occur under the zero-current condition. A design example of the proposed BiDUP converter is presented for medium voltage (MV) and high-power solid-state transformer (SST) systems where both voltage transformation and bidirectional power flow are required. The main features of the proposed converter are to reduce both the switching losses in power semiconductor devices and the filter inductance requirement simultaneously. To verify the feasibility of the proposed converter, a simulation study on the BiDUP converter based SST in a distribution system is presented. Furthermore, to validate the operational principle of the proposed converter, an experimental study using a small-scale prototype is also presented.

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Ichou, Houssam, Daniel Roger, and Mathieu Rossi. "Thermal behavior of grain-oriented electrical steel wound core solid-state transformer." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 41, no. 2 (February 14, 2022): 732–51. http://dx.doi.org/10.1108/compel-06-2021-0223.

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Purpose This paper aims to propose a new design for high-power compact solid-state transformers (SSTs) made with grain-oriented electrical steel (GOES) wound cores that benefit from the natural reduction of iron losses at high temperatures. Design/methodology/approach An experimental approach, coupled with numerical and analytical investigations, is widely used for proving the validity of the proposed concept. Findings With cores much hotter than coils, the new design of medium frequency transformers can be used for building compact SSTs that rated powers and common-mode insulation voltages much higher than existing ones with similar efficiencies. Research limitations/implications The thermal design must provide a large difference between core and coil temperatures in a reasonable volume. Practical implications The increasing number of intermittent renewable sources place electric grid stability at risk. Smart nodes, made of SSTs, improve the global grid stability because they are able to provide real-time control of energy fluxes at critical points. In railway applications, high-power SST cells can be distributed along the train providing a larger volume for passengers. Social implications The increasing part of electricity in a flexible grid requires performant and high-power SSTs made with components that have an environmental footprint as low as possible. Originality/value This paper proves that the design of high-power transformers with GOES wound cores much hotter than coils is possible. It proposes also a thermal equivalent circuit that helps the design.

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Zheng, Gengzhe, Yu Chen, and Yong Kang. "Modeling and control of the modular multilevel converter (MMC) based solid state transformer (SST) with magnetic integration." CES Transactions on Electrical Machines and Systems 4, no. 4 (December 2020): 309–18. http://dx.doi.org/10.30941/cestems.2020.00038.

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Stynski, Sebastian, Marta Grzegorczyk, Cezary Sobol, and Radek Kot. "Current Control Strategies for a Star Connected Cascaded H-Bridge Converter Operating as MV-AC to MV-DC Stage of a Solid State Transformer." Energies 14, no. 15 (July 29, 2021): 4607. http://dx.doi.org/10.3390/en14154607.

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Nowadays, the increasing number of nonlinear loads and renewable energy resources pose new challenges for the standard electrical grid. Conventional solutions cannot handle most of them. The weakest component in the whole system is a conventional distribution (converting medium to low AC voltage) transformer. It should not operate with unbalanced, heavily distorted voltage and cannot control power flow or compensate current harmonics. One of the promising solutions to replace the conventional transformer and thus minimize power flow and grid distortions is a power electronics device called a solid state transformer (SST). Depending on the SST topology, it can have different functionalities, and, with the proper control algorithm, it is able to compensate any power imbalances in both low voltage (LV) and medium voltage (MV) grid sides. In the case of a three energy conversion stage SST, the LV and the MV stages can be treated separately. This paper focuses on the MV-AC to the MV-DC stage only based on a star-connected cascaded H-bridge converter. In this paper, a simple control solution for such a converter enabling different current control strategies to distribute power among the phases in an MV grid in the case of voltage imbalances is proposed. Simulation and experimental results proved good performance and verified the validity of the proposed control algorithm.

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Ronanki, Deepak, Apoorva Kelkar, and Sheldon S. Williamson. "Extreme Fast Charging Technology—Prospects to Enhance Sustainable Electric Transportation." Energies 12, no. 19 (September 29, 2019): 3721. http://dx.doi.org/10.3390/en12193721.

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With the growing fleet of a new generation electric vehicles (EVs), it is essential to develop an adequate high power charging infrastructure that can mimic conventional gasoline fuel stations. Therefore, much research attention must be focused on the development of off-board DC fast chargers which can quickly replenish the charge in an EV battery. However, use of the service transformer in the existing fast charging architecture adds to the system cost, size and complicates the installation process while directly connected to medium-voltage (MV) line. With continual improvements in power electronics and magnetics, solid state transformer (SST) technology can be adopted to enhance power density and efficiency of the system. This paper aims to review the current state of the art architectures and challenges of fast charging infrastructure using SST technology while directly connected to the MV line. Finally, this paper discusses technical considerations, challenges and introduces future research possibilities.

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Banumathy, Jeyapradha Ravichandran, and Rajini Veeraraghavalu. "Optimal design of minimal footprint high frequency transformer." Serbian Journal of Electrical Engineering 18, no. 3 (2021): 303–20. http://dx.doi.org/10.2298/sjee2103303b.

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Transformer design procedure may vary essentially in respect of the transformer type and its operating frequency (ranging between 50/60 Hz and a few megahertz). This paper presents a simple and straightforward method based on the optimal choice of core geometry of a high frequency transformer (HFT) used in Solid State Transformer (SST) applications. The core of SST is the HFT which largely influences its size and overall performance. The proposed design procedure for HFT focuses on optimizing the core geometry coefficient (in cm5) with a constraint inflicted on loss density. The core geometry coefficient has direct impact on the regulation and copper loss and the procedure results in a robust overall design with minimal footprint. Also, the procedure intends to bring all the operating parameters like regulation, losses and temperature rise within permissible limits while retaining desired efficiency. Thus an energy-efficient design is achieved with minimal footprint. The optimization procedure is implemented using recently developed Moth-flame Optimization (MFO) algorithm. The results of the MFO algorithm are compared with the wellestablished PSO technique. An experimental prototype is built to validate the findings.

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Zheng, Zhilong, Rui Liu, Yanlong Qi, Haisheng Lin, Weizhuo Hong, Yuquan Zhu, and Chaoyao Xu. "A novel AC-DC hybrid microgrid architecture and control strategy for electric vehicle swap station." Journal of Physics: Conference Series 2404, no. 1 (December 1, 2022): 012024. http://dx.doi.org/10.1088/1742-6596/2404/1/012024.

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Abstract The characteristics of small volume, modularity, and easy expansion in solid-state transformers (SST), which makes SST widely applied in electric vehicle swapping stations. However, due to various loads and pulsed loads, voltage instability and fluctuation problems inevitably occur in electric vehicle swapping stations. Aiming at these problems, a topology structure based on a Modular Multilevel Solid State Transformer (MMC-SST) is proposed. It is the first choice for realizing the flexible power allocation of AC/DC hybrid system and the interconnection of medium and low voltage. The performance of the DC bus voltage of the charging station has been improved. Based on this topology, an energy management strategy with virtual synchronous generator (VSG) control is proposed to smoothly transition the on-grid and off-grid processes of the distributed power source. In addition, due to the frequency regulation is applied in the control system, the energy storage system has damping and inertia when the output of the new energy power generation equipment changes or load fluctuation, reducing the impact on the load energy storage equipment and improving the stability and safety of the electric vehicle charging station system. Finally, the effectiveness of the proposed topology and its control strategy in different working scenarios are verified by simulation. Simulation analysis shows that the proposed topology has good advantages in DC bus voltage stability, optimization of electric vehicle charging characteristics and load management.

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Ai, Xiaorui, Dongsheng Zuo, and Ye Zhang. "Modeling and Simulation of Dual-Active-Bridge Based on PI Control." Journal of Physics: Conference Series 2221, no. 1 (May 1, 2022): 012007. http://dx.doi.org/10.1088/1742-6596/2221/1/012007.

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Abstract Dual-active-bridge (DAB) is a DC/DC converter,which is commonly used in solid-state-transformer (SST) and electric vehicle (EV).In order to obtain the expected output voltage,the converter needs to be modeled and controlled.Firstly,the working modes in different time intervals of the switching cycle under single-phase-shift (SPS) modulation are analyzed,and the mathematical models of output voltage,current stress and phase-shifting duty cycle are constructed.Then,the simulation model is built on Simulink,and the PI controller is used for closed-loop voltage control,The accuracy of the mathematical model is verified.

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Yoon, Dongkwan, Sungmin Lee, and Younghoon Cho. "Design Considerations of Series-Connected Devices Based LLC Converter." Energies 13, no. 1 (January 5, 2020): 264. http://dx.doi.org/10.3390/en13010264.

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This paper describes the design of a Series-Connected Device based on a fixed–frequency LLC resonant converter (SCDLLC). Isolation of the dc-dc converter like the LLC resonant converter is used for the stability of the high voltage system such as a solid-state-transformer (SST). The series-connected devices driving method is one of the methods applicable to a high voltage system. When driving series-connected devices, an auxiliary circuit for voltage balancing between series-connected devices is required, which can be simply implemented using a passive element. In this paper, LLC converter design with balancing circuits configured in parallel with a device is provided, and both the simulations and experiments were performed.

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Li, Sheng, Zhihao Zhou, Qiqi Shan, and Jiani An. "Analysis of Transient Voltage Stability in a Low Voltage Distribution Network Using SST for the Integration of Distributed Generations." Journal of Electrical and Computer Engineering 2018 (June 3, 2018): 1–9. http://dx.doi.org/10.1155/2018/3498491.

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Models of a low voltage distribution network using a typical tertiary-structure solid state transformer (SST) for the integration of distributed generations (DGs) and a conventional low voltage distribution network integrated with DGs were established to study the transient voltage stability issue, using the power system simulation software PSCAD. Effects on the transient voltage stability of the load bus and DC bus in the SST system are analyzed when grid-side cable line faults (such as short circuit and line disconnection) occur or the total output of DGs drops greatly. The results show that, comparing with the conventional system, the SST has apparent advantages on enhancing the transient voltage stability of load bus while facing different disturbances, even though SST has to regulate the voltage passively. Short circuit faults at different location of the grid-side line have different effects on the transient voltage stability, while the effect of disconnection fault is not related to fault location. Moreover, the DC bus voltage is easy to keep climbing continually when short circuit fault of the line occurs that is close to the SST input stage or disconnection fault occurs at any location of the line. If a battery energy storage station is installed, the transient voltage stability of DC bus and load bus will be improved effectively because of the regulation function of battery storage.

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Cha and Kim. "Voltage Balance Switching Scheme for Series-Connected SiC MOSFET LLC Resonant Converter." Energies 12, no. 20 (October 21, 2019): 4003. http://dx.doi.org/10.3390/en12204003.

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To achieve high efficiency and power density, silicon carbide (SiC)-based Inductor-Inductor-Capacitor (LLC) resonant converters are applied to the DC/DC converter stage of a solid-state transformer (SST). However, because the input voltage of an SST is higher than the rated voltage of a commercial SiC device, it is essential to connect SiC devices in series. This structure is advantageous in terms of voltage rating, but a parasitic capacitance tolerance between series-connected SiC devices causes voltage imbalance. Such imbalance greatly reduces system stability as it causes overvoltage breakdown of SiC device. Therefore, this paper proposes a switching scheme to solve the voltage imbalance between SiC metal-oxide-semiconductor field-effect transistors (MOSFETs). The proposed scheme sequentially turns off series-connected SiC MOSFETs to compensate for the turn-off delays caused by parasitic capacitor tolerances. In addition, dead-time selection methods to achieve voltage balance and zero voltage switching simultaneously are provided in detail. To verify the effectiveness of the proposed scheme, experiments were conducted on a 2 kW series-connected SiC MOSFET LLC resonant converter prototype.

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Oñederra, Oier, Francisco Javier Asensio, Gaizka Saldaña, José Ignacio San Martín, and Inmaculada Zamora. "Wind Energy Harnessing in a Railway Infrastructure: Converter Topology and Control Proposal." Electronics 9, no. 11 (November 18, 2020): 1943. http://dx.doi.org/10.3390/electronics9111943.

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Long distances in the vicinities of railways are not exploited in terms of wind energy. This paper presents a scalable power electronics approach, aimed to harness the wind potential in a railway infrastructure. The key aspect of this proposal relies on both using the wind energy in the location, and the displaced air mass during the movement of a train along the railway, in order to produce electrical energy. Vertical Axis Wind Turbines (VAWT) are used in order to take advantage of the wind power, and widely used and well-known power converter techniques to accomplish the goal, showing MPPT techniques, parallelization of converters and power delivery with a Solid State Transformer (SST). Results are shown according simulations of the whole system, with and without train activity, resulting that 30.6 MWh of the energy could be generated without the train, and the energy generated with the assistance of the train could reach 32.3 MWh a year. Concluding that almost the 10% of the energy could be provided by the assistance of the train.

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Granata, Samuele, Marco Di Benedetto, Cristina Terlizzi, Riccardo Leuzzi, Stefano Bifaretti, and Pericle Zanchetta. "Power Electronics Converters for the Internet of Energy: A Review." Energies 15, no. 7 (April 2, 2022): 2604. http://dx.doi.org/10.3390/en15072604.

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This paper presents a comprehensive review of multi-port power electronics converters used for application in AC, DC, or hybrid distribution systems in an Internet of Energy scenario. In particular, multi-port solid-state transformer (SST) topologies have been addressed and classified according to their isolation capabilities and their conversion stages configurations. Non-conventional configurations have been considered. A comparison of the most relevant features and design specifications between popular topologies has been provided through a comprehensive and effective table. Potential benefits of SSTs in distribution applications have been highlighted even with reference to a network active nodes usage. This review also highlights standards and technical regulations in force for connecting SSTs to the electrical distribution system. Finally, two case studies of multi-port topologies have been presented and discussed. The first one is an isolated multi-port bidirectional dual active bridge DC-DC converter useful in fast-charging applications. The second case of study deals with a three-port AC-AC multi-level power converter in H-Bridge configuration able to replicate a network active node and capable of routing and controlling energy under different operating conditions.

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Mohammed, Ali Basim, Mohd Aifaa Mohd Ariff, and Sofia Najwa Ramli. "Power quality improvement using dynamic voltage restorer in electrical distribution system: an overview." Indonesian Journal of Electrical Engineering and Computer Science 17, no. 1 (January 1, 2020): 86. http://dx.doi.org/10.11591/ijeecs.v17.i1.pp86-93.

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This paper represents a review of the dynamic voltage restorer for power quality improvement in the electrical distribution system. Over the past 50 years, issues concerning power quality have steadily increased, to prevent the effect of the voltage disturbances, some of the devices are put as a solution to these problems such as distribution static compensator (D- STATCOM), solid-state transformer (SST), uninterruptible power supply (UPS), dynamic voltage restorer (DVR). The DVR is one of the economic solutions to overcome the voltage disturbances like voltage sag/swell and harmonics. It is widely used to mitigate the voltage disturbances in the power distribution system, especially in the medium and low distribution networks. This paper aims to review the implementation of the DVR in the system integrated with renewable energy resources. This is important because the future of electricity business is moving towards renewable energy and also provides a thorough discussion of the typical components, controllers, compensation methods, and the application of DVR. The extensive review of the technology aims to ease and speed up the development and the advancement of the DVR in the near future.

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Chen, Hao, and Deepak Divan. "Soft-Switching Solid-State Transformer (S4T)." IEEE Transactions on Power Electronics 33, no. 4 (April 2018): 2933–47. http://dx.doi.org/10.1109/tpel.2017.2707581.

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Peña-Carro, Paula, and Oscar Izquierdo-Monge. "Hybrid AC/DC architecture in the CE.D.E.R.-CIEMAT microgrid: demonstration of the TIGON project." Open Research Europe 2 (October 26, 2022): 123. http://dx.doi.org/10.12688/openreseurope.15154.1.

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This article presents the demonstrative development of the Towards Intelligent DC-based hybrid Grids Optimizing the Network performance (TIGON) project at the Centre for the Development of Renewable Energy - Centre for Energy, Environmental and Technological Research (CE.D.E.R.-CIEMAT), as well as the established objectives to be achieved with the implementation of a microgrid with smart grid architecture based on direct current (DC) and integrated into the current energy system. This type of architecture is proposed as a future solution to reduce energy losses caused by DC-alternating current (AC) conversions, increasing the overall performance and profitability of hybrid grids. All this without forgetting to ensure the supply, stability and reliability of the system with the development of all the necessary equipment and protections to make this approach a reality. The microgrid design and process of implementation start from a transformation centre, from which the medium voltage direct current (MVDC) grid will be created by the solid-state transformer (SST). In the MVDC grid, we will find a bank of lead-acid batteries and other essential equipment in the microgrid, a DC/DC converter that will create the low voltage direct current (LVDC) grid. On the LVDC side, several branches have been designed to connect the rest of the systems: generation (mini-wind and photovoltaic), storage (lithium ferro-phosphate [LFP] batteries) and loads (AC and DC loads). Each of the equipment will have a connection to the DC grid through converters made exclusively for this equipment and connexion to the AC grid, which will allow us to obtain all the necessary data to carry out the required studies to achieve the established objectives of the project.

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Sanduleac, Mihai, Lucian Toma, Mircea Eremia, Irina Ciornei, Constantin Bulac, Ion Triștiu, Andreea Iantoc, João F. Martins, and Vitor F. Pires. "On the Electrostatic Inertia in Microgrids with Inverter-Based Generation Only—An Analysis on Dynamic Stability." Energies 12, no. 17 (August 26, 2019): 3274. http://dx.doi.org/10.3390/en12173274.

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Microgrids are about to change the architecture and the operation principles of the future power systems towards smartness and resiliency. Power electronics technologies are key enablers for novel solutions. In this paper we analyze the benefits of a “microgrid by design” architecture (MDA), using a solid-state transformer (SST) as a low-voltage grid-former and inverter-based generation only. In this context, the microgrid stability is maintained with the help of “electrostatic energy inertia” that can be provided by the capacitor connected to the DC busbar behind the SST inverter topology. This happens in a natural way, alike the mechanical inertia in power systems with synchronous machines, however without depending on frequency and without the need of a rotational inertia. This type of microgrid always operates (both fully connected to the main grid or in islanding mode) with all the necessary mechanisms needed to maintain the microgrid stable—no matter of the perturbations in the upstream of the point of common coupling (PCC). In the case of microgrids with inverter-based generation only (including the energy storage systems), there is no mechanical inertia and different stability mechanisms need to be applied compared to the stability principle of the classical power systems. Our proposed mechanism differentiates from the recently proposed stability assessments of microgrids based on virtual synchronous generators from the control theory perspective. This paper is a continuation of our previous work where the MDA was first introduced. The use-cases and scenarios are based on realistic and yet reasonable complexities, by coupling the disturbance magnitude with the voltage stability limit in power grids. The paper finds meaningful disturbances to test the electrostatic energy inertia at the boundaries of grid stability, as guidance to understand the range of voltage variation for extreme conditions. The results show that in microgrids with inverter-based generation only and passive loads (RLC type) the operation is no longer frequency dependent. The energy of the DC busbar capacitor as electrostatic energy inertia of the MDA has a role similar to that of the rotational machines in classical grids in terms of maintaining dynamic stability, however impacting two different types of stability.

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Cuculić, Aleksandar, JaSMIN Čelić, and Rene Prenc. "Solid State Transformers for Ship’s Electrical Power System." Journal of Maritime & Transportation Science 54, no. 1 (June 2018): 53–60. http://dx.doi.org/10.18048/2018.54.04.

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Traditional transformers have an important role and a long history of use in shipboard power distribution systems. The introduction of fully integrated electrical propulsion systems and other high power nonlinear loads onboard modern vessels, together with increased number of ports with high voltage shore connection systems, causes considerable power quality issues which also affect the operation and the design process of traditional power transformers. Some of the challenges and shortcomings of conventional transformers can be partially overcome by using solid state transformers (SST). Thanks to the availability of advanced power semiconductor devices capable of handling medium voltage levels, there is a significant growth in the use of the SST technology in the smart-grid and traction application. This paper has analysed the possibility of SST implementation on ships.

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37

Zainuddin, Zafirah, Rahimi Baharom, Ihsan Mohd Yassin, and Khairul Safuan Muhammad. "Solid-State Transformer (S2T) of Single Phase Matrix Converter." International Journal of Power Electronics and Drive Systems (IJPEDS) 9, no. 3 (September 1, 2018): 997. http://dx.doi.org/10.11591/ijpeds.v9.i3.pp997-1005.

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<span lang="EN-US">Solid-State Transformer (S2T) also known as Power Electronic Transformer (PET) is applied in various industrial fields compared to the conventional transformer due to it flexible voltage transfer ratio, high power density, and low harmonic distortion. This paper presents the S2T of Single Phase Matrix Converter (SPMC) that acts as cyclo-converter. A 1kHz frequency was synthesized on the primary side of the transformer using Pulse Width Modulation (PWM) technique, whilst, the output converted by the SPMC that produces the 50Hz frequency. A part of AC to AC operation, the switching algorithm for safe-commutation technique is also presented to solve the commutation problem caused by the usage of inductive load. Minimization of size, losses and optimal efficiency are the advantages of this approach. The proposed model was simulated by using MATLAB/Simulink (MLS).</span>

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38

Shamshuddin, Mohammed Azharuddin, Felix Rojas, Roberto Cardenas, Javier Pereda, Matias Diaz, and Ralph Kennel. "Solid State Transformers: Concepts, Classification, and Control." Energies 13, no. 9 (May 7, 2020): 2319. http://dx.doi.org/10.3390/en13092319.

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Increase in global energy demand and constraints from fossil fuels have encouraged a growing share of renewable energy resources in the utility grid. Accordingly, an increased penetration of direct current (DC) power sources and loads (e.g., solar photovoltaics and electric vehicles) as well as the necessity for active power flow control has been witnessed in the power distribution networks. Passive transformers are susceptible to DC offset and possess no controllability when employed in smart grids. Solid state transformers (SSTs) are identified as a potential solution to modernize and harmonize alternating current (AC) and DC electrical networks and as suitable solutions in applications such as traction, electric ships, and aerospace industry. This paper provides a complete overview on SST: concepts, topologies, classification, power converters, material selection, and key aspects for design criteria and control schemes proposed in the literature. It also proposes a simple terminology to identify and homogenize the large number of definitions and structures currently reported in the literature.

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Chen, Hao, and Deepak Divan. "Design of a 10-kV·A Soft-Switching Solid-State Transformer (S4T)." IEEE Transactions on Power Electronics 33, no. 7 (July 2018): 5724–38. http://dx.doi.org/10.1109/tpel.2017.2749430.

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Sanduleac, Mihai, João Martins, Irina Ciornei, Mihaela Albu, Lucian Toma, Vitor Pires, Lenos Hadjidemetriou, and Rooktabir Sauba. "Resilient and Immune by Design Microgrids Using Solid State Transformers." Energies 11, no. 12 (December 3, 2018): 3377. http://dx.doi.org/10.3390/en11123377.

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Solid State Transformers (SST) may become, in the near future, key technological enablers for decentralized energy supply systems. They have the potential to unleash new technologies and operation strategies of microgrids and prosumers to move faster towards a low carbon-based economy. This work proposes a paradigm change in the hierarchically and distributed operated power systems where SSTs are used to asynchronously connect the many small low voltage (LV) distribution networks, such as clusters of prosumers or LV microgrids, to the bulk power system. The need for asynchronously coupled microgrids requires a design that allows the LV system to operate independently from the bulk grid and to rely on its own control systems. The purpose of this new approach is to achieve immune and resilient by design configurations that allow maximizing the integration of Local Renewable Energy Resources (L-RES). The paper analyses from the stability point of view, through simplified numerical simulations, the way in which SST-interconnected microgrids can become immune to disturbances that occur in the bulk power system and how sudden changes in the microgrid can damp out at the Point of Common Coupling (PCC), thus achieving better reliability and predictability in both systems and enabling strong and healthy distributed energy storage systems (DESSs). Moreover, it is shown that in a fully inverter-based microgrid there is no need for mechanical or synthetic inertia to stabilize the microgrid during power unbalances. This happens because the electrostatic energy stored in the capacitors connected behind the SST inverter can be used for a brief time interval, until automation is activated to address the power unbalance for a longer term.

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Trushkin, V., S. Shlyupikov, G. Eroshenko, M. Levin, and S. Kifarak. "Moisture content as an important integral parameter of transformer oil quality in power transformers of 10/0.4 kV substations." E3S Web of Conferences 124 (2019): 05008. http://dx.doi.org/10.1051/e3sconf/201912405008.

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The main element characterizing the transformer efficiency is the state of its isolation, and the first thing is operating oil, which can perform its functions for a long time with timely restoration of its properties. Transformer oil is the main dielectric being in contact with the external environment, interacting with solid insulation and carrying a large amount of diagnostic information. Analysis of the development of transformer insulation damage showed that the main catalyst for accelerating the aging process of the oil is the appearance of moisture in it. This effect is enhanced by oxygen, temperature, the catalytic action of metals, oxidation and other factors. To confirm the influence of moisture content in oil on the deterioration of its properties, a statistical analysis of the oil sample test protocols was carried out. The obtained data allowed us to determine the moisture content as an important integral parameter of oil quality. Recommendations are given on the inclusion of a moisture content parameter in a set of mandatory requirements, in particular, for 10/0.4 kV consumer transformer substations equipped with silica gel air dryers

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Shugart, Kathleen N., Gerard M. Ludtka, Gail Mackiewicz-Ludtka, and William A. Soffa. "Exchange Coupling Nanophase Fe-Pd Ferromagnets Through Solid State Transformation." Solid State Phenomena 172-174 (June 2011): 273–78. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.273.

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This study continues previous work on off-stoichiometric Fe-Pd alloys using a combined reaction strategy during thermomechanical processing [1,2]. Severe plastic deformation of the initial disordered fcc gamma phase (γ) of compostion Fe-35at.%Pd, followed by heat treatment in the two phase field produces a nano-composite ferromagnet comprised of soft alpha phase/ferrite (α) in a high-anisotropy L10 FePd matrix. The length scale and morphology of the transformation products have been characterized using x-ray diffraction, and scanning electron microscopy. The transformed microstructures exhibit strong texture retention similar to the stoichiometric alloy suggesting a massive ordering mode. The alloy has shown a proclivity to exchange couple at a length scale not in agreement with proposed theories of exchange coupling [3,4]. The magnetic properties were measured using standard vibrating sample magnetometry (VSM). This research has been supported by the National Science Foundation (NSF-DMR).

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Liu, Yupeng, Wencheng Wang, Yushan Liu, and Sertac Bayhan. "Real-time implementation of finite control set model predictive control for matrix converter based solid state transformer." International Journal of Hydrogen Energy 42, no. 28 (July 2017): 17976–83. http://dx.doi.org/10.1016/j.ijhydene.2017.04.293.

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Zhang, Yu, and Jinliang Liu. "High-voltage pulse modulator based on cylindrical self-coupling saturable pulse transformer and solid-state Marx generator." Laser and Particle Beams 32, no. 1 (January 14, 2014): 99–108. http://dx.doi.org/10.1017/s0263034613001031.

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AbstractHigh-voltage pulse modulator has broad applications in industry. In order to pursue the qualities of compactness, solidification, and long life time, a high-voltage pulse modulator based on a helical Blumlein pulse forming line (HBPFL),a Marx generator and a self-coupling saturable pulse transformer (SPT) with fully cylindrical coaxial conductors is put forward and investigated in this paper. A new method that the fully cylindrical SPT simultaneously works as the charging pulse transformer and magnetic switch of the HBPFL is put forward and demonstrated. Traditional spark gap is substituted by the SPT to enable the features of solidification, compactness, and long life time of the modulator. Experimental results showed that the SPT had good response characteristics to short sinusoidal pulse and 100 ns-range square pulses. The fully cylindrical SPT driven by the 50–70 kV Marx generator can suppress the saturated inductance of the secondary windings to a level less than 500 nH, due to the strong reversed mutual induction between cylindrical windings after the core saturated. It also demonstrated that the pulse modulator was able to deliver a high-voltage pulse to a 160 Ω load, with amplitude of 148 kV, pulse duration of 130 ns, and pulse rise time ranging from 60 to 105 ns.

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Jirková, Hana, Kateřina Rubešová, Vít Pileček, and Mária Behúlová. "Steels with High Temperature Carbides - New Possibilities for Semi-Solid State Processing." Solid State Phenomena 217-218 (September 2014): 325–31. http://dx.doi.org/10.4028/www.scientific.net/ssp.217-218.325.

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Semi-solid processing of steels is typically studied using high-alloy steels with higher carbon levels, as those offer a long freezing range which is favourable for conducting the process. The drawback to their application is their microstructure which typically consists of austenite grains embedded in ledeburitic network. This type of microstructure typically fails in brittle manner by fracturing along the interface of the hard network and ductile austenite grains. This is why a way was sought to altering or even inverting the configuration of the microstructure. Eventually, suitable steel chemistries were found which allow the inverted microstructure to be obtained. With regard to the high content of alloy additions, these steels have to be made by powder metallurgy methods. Five different steels of this kind were selected for the experimental programme. All contained high amounts of alloying elements and a large fraction of carbides. Their carbon content was taken into account as well, ranging from 0.55 to 3.4 %. Differences between the steels consisted in the levels of major alloying elements, namely chromium, vanadium, molybdenum, tungsten and cobalt. After suitable process parameters were found, semi-solid processing was used to prepare demonstration products. The transition through semi-solid state transformed the ferritic matrix to austenitic-martensitic one, in which the high-stability carbides were retained. The resulting microstructures were of unconventional nature where carbide particles were embedded in tough metal matrix. Their configuration was thus inverted in contrast to the ones typically obtained by semi-solid processing of tool steels.

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Das, Prosenjit, Sudip K. Samanta, Himadri Chattaopadhyay, Pradip Dutta, and Nilkanta Barman. "Rheological Characterization of Semi-Solid A356 Aluminium Alloy." Solid State Phenomena 192-193 (October 2012): 329–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.192-193.329.

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Rheological behavior of semi-solid slurries forms the backbone of semi-solid processing of metallic alloys. In particular, the effects of several process and metallurgical parameters such as shear rate, shear time, temperature, rest time and size, distribution and morphology of the primary phase on the viscosity of the slurry needs in-depth characterization. In the present work, rheological behaviour of the semisolid aluminium alloy (A356) slurry is investigated by using a high temperature Searle type Rheometer using concentric cylinders. Three different types of experiment are carried out: isothermal test, continuous cooling test and steady state test. Continuous decrease in viscosity is observed with increasing shear rate at a fixed temperature (isothermal test). It is also found that the viscosity increases with decreasing temperature for a particular shear rate due to increasing solid fraction (continuous cooling test). Thixotropic nature of the slurry is confirmed from the hysteresis loops obtained during experimentation. Time dependence of slurry viscosity has been evaluated from the steady state tests. After a longer shearing time under isothermal conditions the starting dendritic structure of the said alloy is transformed into globular grains due to abrasion, agglomeration, welding and ripening.

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Zheng, Liran, Xiangyu Han, Zheng An, Rajendra Prasad Kandula, Karthik Kandasamy, Maryam Saeedifard, and Deepak Divan. "SiC-Based 5-kV Universal Modular Soft-Switching Solid-State Transformer (M-S4T) for Medium-Voltage DC Microgrids and Distribution Grids." IEEE Transactions on Power Electronics 36, no. 10 (October 2021): 11326–43. http://dx.doi.org/10.1109/tpel.2021.3066908.

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Malinowski, M. "Cascaded multilevel converters in recent research and applications." Bulletin of the Polish Academy of Sciences Technical Sciences 65, no. 5 (October 1, 2017): 567–78. http://dx.doi.org/10.1515/bpasts-2017-0062.

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Abstract Multilevel converters have been intensively investigated and developed since 1960s and have found successful industrial applications. The aim of this paper is to present state of the art as well as recent research and applications of cascaded multilevel converters, which are a very interesting solution for power distribution systems and renewable energy sources. Cascaded multilevel converters can easily operate at medium and high voltage based on the series connection of power modules (cells), which use standard low-voltage component configurations. Series connections of modules (cells) allow for high quality output voltages and input currents, reduction of passive components and availability of component redundancy. Due to these features the cascaded multilevel converters have been recognized as attractive solutions for high-voltage direct-current (HVDC) transmission, solid state transformers (SST) and photovoltaic (PV) systems.

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Mughees, Mariam, Munazza Sadaf, Hasan Erteza Gelani, Abdullah Bilal, Faisal Saeed, Md Shahariar Chowdhury, Kuaanan Techato, Sittiporn Channumsin, and Nasim Ullah. "Comparison of Efficiency-Based Optimal Load Distribution for Modular SSTs with Biologically Inspired Optimization Algorithms." Electronics 11, no. 13 (June 24, 2022): 1988. http://dx.doi.org/10.3390/electronics11131988.

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The battle of currents between AC and DC reignited as a result of the development in the field of power electronics. The efficiency of DC distribution systems is highly dependent on the efficiency of distribution converter, which calls for optimized schemes for the efficiency enhancement of distribution converters. Modular solid-state transformers (SSTs) play a vital role in DC distribution networks and renewable energy systems (RES). This paper deals with efficiency-based load distribution for solid-state transformers (SSTs) in DC distribution networks. The aim is to achieve a set of minimum inputs that are consistent with the output while considering the constraints and efficiency. As the main feature of modularity is associated with a three-stage structure of SSTs, this modular structure is optimized using ant lion optimizer (ALO) and validated by applying it to the EIA (Energy Information Agency) DC distribution network which contains SSTs. In the DC distribution grid, modular SSTs provide the promising conversion of DC power from medium voltage to lower DC range (400 V). The proposed algorithm is simulated in MATLAB and also compared with two other metaheuristic algorithms. The obtained results prove that the proposed method can significantly reduce the input requirements for producing the same output while satisfying the specified constraints.

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Mortazavizadeh, Seyed Abolfazl, Simone Palazzo, Arturo Amendola, Enzo De Santis, Dario Di Ruzza, Giuseppe Panariello, Annunziata Sanseverino, Francesco Velardi, and Giovanni Busatto. "High Frequency, High Efficiency, and High Power Density GaN-Based LLC Resonant Converter: State-of-the-Art and Perspectives." Applied Sciences 11, no. 23 (November 30, 2021): 11350. http://dx.doi.org/10.3390/app112311350.

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Abstract:

Soft switching for both primary and secondary side devices is available by using LLC converters. This resonant converter is an ideal candidate for today’s high frequency, high efficiency, and high power density applications like adapters, Uninterrupted Power Supplies (UPS), Solid State Transformers (SST), electric vehicle battery chargers, renewable energy systems, servers, and telecom systems. Using Gallium-Nitride (GaN)-based power switches in this converter merits more and more switching frequency, power density, and efficiency. Therefore, the present paper focused on GaN-based LLC resonant converters. The converter structure, operation regions, design steps, and drive system are described precisely. Then its losses are discussed, and the magnets and inductance characteristics are investigated. After that, various interleaved topologies, as a solution to improve power density and decrease current ripples, have been discussed. Also, some challenges and concerns related to GaN-based LLC converters have been reviewed. Commercially available power transistors based on various technologies, i.e., GaN HEMT, Silicon (Si) MOSFET, and Silicon Carbide (SiC) have been compared. Finally, the LLC resonant converter has been simulated by taking advantage of LTspice and GaN HEMT merits, as compared with Si MOSFETs.

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Journal articles on the topic 'Solid-state transformer (SST)'

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