State of the art of solid-state transformers: Advanced topologies, implementation issues, recent progress and improvements
TL;DR: This review comprehensively reviews the SST topologies suitable for different voltage levels and with varied stages, their control operation, and different trends in applications and provides recommendations for the improvement of future SST configuration and development.
Abstract: Solid-state transformer (SST) is an emerging technology integrating with a transformer power electronics converters and control circuitry. This paper comprehensively reviews the SST topologies suitable for different voltage levels and with varied stages, their control operation, and different trends in applications. The paper discusses various SST configurations with their design and characteristics to convert the input to output under unipolar and bipolar operation. A comparison between the topologies, control operation and applications are included. Different control models and schemes are explained. Potential benefits of SST in many applications in terms of controllability and the synergy of AC and DC systems are highlighted to appreciate the importance of SST technologies. This review highlights many factors including existing issues and challenges and provides recommendations for the improvement of future SST configuration and development.
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TL;DR: In this paper, a solid-state transformer (SST) was used for solar power station design and an energy management strategy (EMS) for the SST was proposed to find the upper and lower bounds of flexible sources.
Abstract: This study introduces a type of solid-state transformer (SST) for solar power station design and an energy management strategy (EMS) for the SST. The purpose of this study is to design a real efficient EMS for the photovoltaic-assisted charging station in smart grid ancillary services and apply the optimal decision method. Also, the energy bound calculation (EBC) model is proposed to find the upper and lower bounds of flexible sources. Also, taking into account the EBC results and the power order from the aggregator, a charge power allocation algorithm is designed to distribute the power of flexible electric vehicles (EVs). With the help of a case study and laboratory analysis, the proposed EMS strategy is effective in real-time energy management and is suitable for practical applications. The obtained results show the stable performance in the calculation of the energy range and real-time power allocation which improves the efficiency of the photovoltaic-based charging station. Also, the SST improves the operation of charge stations for supplying the sustaining power.
39 citations
TL;DR: 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.
Abstract: 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.
38 citations
36 citations
18 Jun 2020
TL;DR: In this article, an integrated solid-state transformer (I-SST) with high-frequency isolation for electric vehicle (EV) fast-charging applications is proposed, which is easily scalable to several hundreds of kilowatts and is ideal for high-power level-3 EV fastcharging stations.
Abstract: In this article, an integrated solid-state transformer (I-SST) with high-frequency (HF) isolation for electric vehicle (EV) fast-charging applications is proposed In the approach proposed in this article, a three-phase I-SST is used as HF galvanic isolation for the system with respect to the medium-voltage grid A direct multipulse ac–dc rectifier is shown to eliminate low-order harmonics in the input current over a wide range of output dc voltage variation The proposed approach has the following advantages: no dc link, hence no bulky electrolytic capacitors, galvanic isolation is via a three-phase HF transformer, high-power density, and simple control scheme for regulating output voltage The approach is easily scalable to several hundreds of kilowatts and is ideal for high-power level-3 EV fast-charging stations A simplified output voltage regulation scheme for the proposed topology is discussed Regulating the output voltage enables the circuit to be used as a direct topology for level-3 charge stations with ac bus architecture Experimental results on a scale down laboratory prototype at 208 V, 15 kW are discussed 1
30 citations
Cites methods from "State of the art of solid-state tra..."
...The proposed I-SST differs from the traditional solidstate transformer (SST) approaches presented in [14]–[17], where more complex control and power stages are employed....
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TL;DR: In this article, the authors present a comprehensive review of soft open point (SOP), an emerging power electronics technology to maximize future distribution networks resiliency and flexibility as well as increase hosting capacity for distributed energy resources like photovoltaics and electric vehicles.
Abstract: The main objective of this article is to present a comprehensive review of soft open point (SOP), an emerging power electronics technology to maximize future distribution networks’ (DNs) resiliency and flexibility as well as increase hosting capacity for distributed energy resources like photovoltaics and electric vehicles. The SOP is currently an active area of research and ongoing development of new control techniques for SOP and optimization algorithm for the optimal use of SOP in DNs produces new techniques until DN operators use it comprehensively in their systems. The motivation for this work is to present the research that has been completed for the SOP and summarize the duties of SOP in DNs according to the literature and propose advanced duties for SOP according to modern standards. Finally, future research directions are mentioned to pave the way for research in the coming years to drive the DNs towards more flexibility and ‘Robust’ from controllability, stability, and protection structure point of view.
22 citations
References
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01 Jan 2011
TL;DR: The architecture described in this paper is a roadmap for a future automated and flexible electric power distribution system that is suitable for plug-and-play of distributed renewable energy and distributed energy storage devices.
Abstract: This paper presents an architecture for a future electric power distribution system that is suitable for plug-and-play of distributed renewable energy and distributed energy storage devices. Motivated by the success of the (information) Internet, the architecture described in this paper was proposed by the NSF FREEDM Systems Center, Raleigh, NC, as a roadmap for a future automated and flexible electric power distribution system. In the envisioned “Energy Internet,” a system that enables flexible energy sharing is proposed for consumers in a residential distribution system. The key technologies required to achieve such a vision are presented in this paper as a result of the research partnership of the FREEDM Systems Center.
1,237 citations
"State of the art of solid-state tra..." refers background or methods in this paper
...[13] developed a 15-kV SiC MOSFET-based single-phase SST topology....
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...A number of SST projects have been developed to facilitate the integration of renewable energy and energy storage systems [13]....
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...All types of SSTs have the functions of isolated AC-AC conversion regardless of their differences in the design of converter topologies [13]....
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...However, it still requires more research in order to improve the SST performance and to achieve cost reduction using different approaches [13]....
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01 Jan 2009
TL;DR: In this paper, the authors present a tutorial on multilevel converters, covering the operating principle, modulation methods, technical issues and industry applications for high power and power-quality demanding applications.
Abstract: Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorialonthistechnology,coveringtheoperatingprincipleand the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.
928 citations
TL;DR: In this article, the authors present a systematical technology review essential for the development and application of SST in the distribution system, including high-voltage power devices, high-power and high-frequency transformers, ac/ac converter topologies, and future research directions.
Abstract: The solid-state transformer (SST), which has been regarded as one of the 10 most emerging technologies by Massachusetts Institute of Technology (MIT) Technology Review in 2010, has gained increasing importance in the future power distribution system. This paper presents a systematical technology review essential for the development and application of SST in the distribution system. The state-of-the-art technologies of four critical areas are reviewed, including high-voltage power devices, high-power and high-frequency transformers, ac/ac converter topologies, and applications of SST in the distribution system. In addition, future research directions are presented. It is concluded that the SST is an emerging technology for the future distribution system.
897 citations
"State of the art of solid-state tra..." refers background in this paper
...Core-type has greater insulation between primary and secondary sides; shell-type could provide better mechanical protection; matrix-type has the multiple cores which have the capability for inter-wiring features that help to reduce leakage inductance and winding AC resistance [34], [94]....
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...To minimize the core loss and avoid core saturation for the nominal operation points, the core material must be selected carefully as it affects the size, power density, and power loss in the transformer [34], [85]....
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...SST increases the system complexity; however, it has few advantages such as reactive power compensation [34]....
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TL;DR: In this paper, the authors proposed a voltage and power balance control for the cascaded H-Bridge converter-based solid-state transformer (SST) based on the single-phase dq model, which can balance the rectifier capacitor voltages and the real power through parallel DAB modules.
Abstract: The solid-state transformer (SST) is an interface device between ac distribution grids and dc distribution systems. The SST consists of a cascaded multilevel ac/dc rectifier stage, a dual active bridge (DAB) converter stage with high-frequency transformers to provide a regulated 400-V dc distribution, and an optional dc/ac stage that can be connected to the 400-V dc bus to provide residential 120/240 V $_{\rm ac}$ . However, due to dc-link voltage and power unbalance in the cascaded modules, the unbalanced dc-link voltages and power increase the stress of the semiconductor devices and cause overvoltage or overcurrent issues. This paper proposes a new voltage and power balance control for the cascaded H-Bridge converter-based SST. Based on the single-phase dq model, a novel voltage and the power control strategy is proposed to balance the rectifier capacitor voltages and the real power through parallel DAB modules. Furthermore, the intrinsic power constraints of the cascaded H-Bridge voltage balance control are derived and analyzed. With the proposed control methods, the dc-link voltage and the real power through each module can be balanced. The SST switching model simulation and the prototype experiments are presented to verify the performance of the proposed voltage and power balance controller.
541 citations
TL;DR: In this article, the authors evaluate three-level topologies as alternatives to two level topologies in converters for lowvoltage applications and compare them for a grid interface, a conventional drive application, and a high speed drive application.
Abstract: This paper evaluates three-level topologies as alternatives to two-level topologies in converters for low-voltage applications. Topologies, semiconductor losses, filter aspects, part count, initial cost, and life-cycle cost are compared for a grid interface, a conventional drive application, and a high-speed drive application.
536 citations