A Power Electronic-Based Distribution Transformer
TL;DR: In this paper, a new kind of distribution transformer is proposed for the twenty-first century, one that can be made self-regulating, oil-free, and able to correct power quality problems.
Abstract: The distribution transformer has been in use by utilities throughout the twentieth century. Until now, it has consisted of a configuration of iron or steel cores and copper/aluminum coils, with mineral oil serving as both coolant and dielectric medium. Inherent in this type of construction are regulation, significant weight, losses, environmental concerns, and power quality issues. A new kind of distribution transformer is proposed for the twenty-first century, one that can be made self-regulating, oil-free, and able to correct power quality problems. A power electronic transformer has been analyzed, simulated, prototyped, and tested. Results of this effort, as well as the novel features of this new type of transformer, are discussed herein.
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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
Cites background from "A Power Electronic-Based Distributi..."
...Although the SST can be constructed from silicon devices operating at lower frequencies [1], this construction requires either serial connections or a multilevel converter topology....
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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
Cites background from "A Power Electronic-Based Distributi..."
...One possible solution is to adopt modular structures (series connection of converters) or multilevel converters with low-voltage and high-speed power device [7]....
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TL;DR: A unique vision for the future of smart transmission grids is presented in which their major features are identified and each smart transmission grid is regarded as an integrated system that functionally consists of three interactive, smart components.
Abstract: A modern power grid needs to become smarter in order to provide an affordable, reliable, and sustainable supply of electricity. For these reasons, considerable activity has been carried out in the United States and Europe to formulate and promote a vision for the development of future smart power grids. However, the majority of these activities emphasized only the distribution grid and demand side leaving the big picture of the transmission grid in the context of smart grids unclear. This paper presents a unique vision for the future of smart transmission grids in which their major features are identified. In this vision, each smart transmission grid is regarded as an integrated system that functionally consists of three interactive, smart components, i.e., smart control centers, smart transmission networks, and smart substations. The features and functions of each of the three functional components, as well as the enabling technologies to achieve these features and functions, are discussed in detail in the paper.
894 citations
Cites background from "A Power Electronic-Based Distributi..."
...Solid-state transformers are used to replace traditional electromagnetic transformers to provide flexible and efficient transformation between different voltage levels [35]....
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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, a single-phase d-q vector-based common duty-ratio control method for the multilevel rectifier, and a voltage feedforward and feedback based controller for the modular DAB converter are presented.
Abstract: The solid-state transformer (SST) is one of the key elements in power electronic-based microgrid systems. The single-phase SST consists of a modular multilevel ac-dc rectifier, a modular dual active bridge (DAB) dc-dc converter with high-frequency transformers, and a dc-ac inverter stage. However, due to dc bus voltage and power unbalancing in each module, the modular SST often presents instability problems making its design difficult and causing unpredictable behavior. Moreover, the unbalanced dc-link voltages increase the stress of the semiconductor devices, and also cause high harmonic distortions of grid current, therefore, necessitating the use of a bigger ac filter. This paper presents a novel single-phase d-q vector-based common-duty-ratio control method for the multilevel rectifier, and a voltage feedforward and feedback based controller for the modular DAB converter. With the proposed control methods, the dc-link voltage and power in each module can be balanced. In addition, the low-distortion grid current, unity power factor, and bidirectional power flow can be achieved. Simulation and experimental results are presented to validate the proposed control methods.
338 citations
References
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01 Jan 1976
1,224 citations
"A Power Electronic-Based Distributi..." refers background in this paper
...As the design matures, one interesting concern is whether the high-bandwidth constant power nature of the load could lead to negative impedance instabilities such are commonly seen in dc systems [8], and occasionally in power-electronics based ac systems [9]....
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Book•
01 Jan 1991
TL;DR: In this paper, the authors present a review of semiconductor devices and their properties, including gate and base drives, and power transistors, as well as feedback control design and an overview of ancillary issues.
Abstract: 1. Introduction. 2. Form and Function: An Overview. 3. Introduction to Rectifier Circuits. 4. Bridge and Polyphase Rectifier Circuits. 5. Phase-Controlled Converters. 6. High-Frequency Switching dc/dc Converters. 7. Isolated High-Frequency dc/dc Converters. 8. Variable-Frequency dc/ac Converters. 9. Resonant Converters. 10. ac/ac Converters. 11. Dynamics and Control: An Overview. 12. State-Space Models. 13. Linear and Piecewise Linear Models. 14. Feedback Control Design. 15. Components: An Overview. 16. Review of Semiconductor Devices. 17. Power Diodes. 18. Power Transistors. 19. Thyristors. 20. Magnetic Components. 21. Ancillary Issues: An Overview. 22. Gate and Base Drives. 23. Thyristor Commutation Circuits. 24. Snubber Circuits and Clamps. 25. Thermal Modeling and Heat Sinking.
1,104 citations
"A Power Electronic-Based Distributi..." refers background in this paper
...[4] J. G. Kassakian, M. F. Schlecht, and G. C. Verghese,Principles of Power Electronics....
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...A convenient way of quantifying this is by the stress factor defined by Kassakian [4]....
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...fying this is by the stress factor defined by Kassakian [4]....
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TL;DR: In this paper, the concept of electronic transformers is further extended and explored for its suitability in power distribution systems, and it is shown that a transformer with a conventional grain-oriented silicon-steel core can process three times the power at 1 kHz operating frequency as compared to 60 Hz.
Abstract: A transformer performs many functions such as voltage transformation, isolation and noise decoupling, and it is an indispensable component in electric power distribution systems. However, at low frequencies (60/50 Hz), it is a bulky and expensive component. In this paper, the concept of electronic transformers is further extended and explored for its suitability in power distribution systems. It should be noted that from the input/output behavior, the electronic transformer and the conventional transformer are identical. Possible topologies employing static converters connected on the primary and secondary sides are explored to realize high-frequency operation of the magnetic core. To assist the commutation process, a four-step switching has been developed which does not require the use of snubbers. Reduced size, losses, higher efficiency, and better voltage regulation are some of the advantages of this approach. A 10 kVA design example along with experiment results are discussed. It is shown that a transformer designed with a conventional grain-oriented silicon-steel core can process three times the power at 1 kHz operating frequency as compared to 60 Hz. The proposed method is scalable in voltage/current with the currently available insulated gate bipolar transistor (IGBT) devices connected in series without special snubbers.
320 citations
05 Oct 1997
TL;DR: In this paper, the concept of electronic transformers is further discussed and several possible topologies employing static power converters connected on the primary and secondary side in combination with magnetic circuits are explored to realize a high-frequency AC link.
Abstract: A power transformer performs many functions such as voltage transformation, isolation, noise decoupling and is an indispensable component in electricity distribution systems. However, at low frequencies (60/50 Hz) it is a bulky and expensive component. In this paper, the concept of electronic transformers is further discussed. Several possible topologies employing static power converters connected on the primary and secondary side in combination with magnetic circuits are explored to realize a high-frequency AC link. The focus of this paper is to realize an electronic transformer as a power delivery component in an electric distribution system. Reduced size, losses, higher efficiency and better voltage regulation are some of the advantages of this approach. A 10 kVA design example along with preliminary experiment results is discussed. It is shown that a transformer designed with a conventional grain-oriented silicon steel core can process three times the power at 1 kHz operating frequency compared to 60 Hz.
172 citations
"A Power Electronic-Based Distributi..." refers background in this paper
...Another attempt at high-power ac/ac conversion has been recently proposed in [5]....
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23 Jun 1986
TL;DR: In this paper, an ac to dc power conditioner, which draws sinusoidal input current, is described and analyzed, and two control loops are used: an inner quantized-gain current program loop uses variable hysteresis to improve noise immunity, and a digital proportional-integral control provides output voltage regulation by adjusting the gain of the program loop.
Abstract: An ac to dc power conditioner, which draws sinusoidal input current, is described and analyzed. Two control loops are used. The inner quantized-gain current program loop uses variable hysteresis to improve noise immunity. Digital proportional-integral control provides output voltage regulation by adjusting the gain of the current program loop.
118 citations