High-Frequency-Link DC Transformer Based on Switched Capacitor for Medium-Voltage DC Power Distribution Application

Zhao, Biao; Song, Qiang; Li, Jianguo; Liu, Wenhua; Liu, Guowei; Zhao, Yuming

doi:10.1109/tpel.2015.2483543

Cited by 131 publications

(44 citation statements)

References 26 publications

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“…Replacing the average value in (2) and (3) with the individual SM capacitor voltages, yields (7) which describes the voltage relationship in each switching cycle Ts (in this example Ts is five times the effective cycle Te). In the matrix, "A5, 4" denotes there are five SMs switched into the stack for the negative stage and four for the positive stage.…”

Section: Operating Principles and Modulation Schemesmentioning

confidence: 99%

An Isolated Resonant Mode Modular Converter With Flexible Modulation and Variety of Configurations for MVDC Application

Xiang

Zhang

Chaffey

et al. 2018

IEEE Trans. Power Delivery

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The dc tap or dc transformer will play an important role in interfacing different voltages of dc links in dc grids. This paper presents an isolated resonant mode modular converter (RMMC) with flexible modulation and assorted configurations to satisfy a wide variety of interface requirements for medium voltage dc (MVDC) networks. The transformer-less RMMC, as introduced in the literature, implemented a restricted modulation scheme leading to a very limited range of step-ratio and the diode rectifier resulted in unidirectional power flow. Both of these limitations are removed in this proposal and galvanic isolation has also been added. Moreover, this new RMMC approach can serve as a building block for variety of configurations. Two such derived topologies are given, which inherently balance the voltage and current between different constituent circuits and realize the high power rating conversion for very low or very high step-ratio application. The theoretical analysis is validated by a set of full-scale simulations and a down-scaled experimental prototype. The results illustrate that this isolated RMMC and its derivatives have promising features for dc taps or dc transformers in MVDC applications.

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Section: Operating Principles and Modulation Schemesmentioning

confidence: 99%

An Isolated Resonant Mode Modular Converter With Flexible Modulation and Variety of Configurations for MVDC Application

Xiang

Zhang

Chaffey

et al. 2018

IEEE Trans. Power Delivery

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show abstract

“…As newer research on dual active bridge-type DC-DC converter applications to renewable energies and electric vehicles comes out [1][2][3], the performance requirements of converters are increasingly becoming higher and higher [4]. This implies a profound study and development of improved medium frequency transformers (MFTs) [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Nanocrystalline and Silicon Steel Medium-Frequency Transformers Applied to DC-DC Converters: Analysis and Experimental Comparison

et al. 2019

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High performance, highly efficient DC-DC converters play a key role in improving the penetration of renewable energy sources in the context of smart grids in applications such as solid-state transformers, built-in power drives in electric vehicles and interfacing photovoltaic and wind-power systems. Advanced medium-frequency transformers (MFTs) are fundamental to enhance DC-DC converters and determining its behavior, therefore MFT design procedures have become increasingly important in this context. This paper investigates which type of core material, between nanocrystalline and silicon steel, has the best properties for designing MFTs for distinct applications. Unlike to other proposals, in this work, two 1 kVA-120 V/240 V-1 kHz lab MFT prototypes, with a different type of core material, are developed for the purpose of comparing its physical characteristics, behavior, and performance under real-life conditions. A final section, the experimental results show that the nanocrystalline MFT has greater power density and efficiency. The results of this work introduce nanocrystalline MFTs as an option in a wider range of applications in niches in which other materials are currently used.

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“…Since the switching frequency is usually from several kHz to hundreds of kHz, the overall size can be reduced and the power density can be increased [4]. In terms of dynamic control for DAB converters, there are two modes of control that are usually employed: voltage mode and current mode [5][6][7][8][9][10][11][12]. Assume that power transmission is from the medium voltage DC (MVDC) side to the low voltage DC (LVDC) side.…”

Section: Introductionmentioning

confidence: 99%

“…In this context, a feedback current mode controller is usually employed. For example, in [8], the LVDC current was necessary for the dual-loop cascade controller; in [9], the instantaneous primary current was sampled at a certain instant for use in a predictive controller, etc.…”

Section: Introductionmentioning

confidence: 99%

“…It is worth noting that the control techniques mentioned in [6][7][8][9] required the information of the terminal current or the transmission current for the control system in one way or another. The two currents, one is AC at the switching frequency whereas the other is DC but contains a high ripple at double switching frequency, require expensive and high bandwidth current transducers to be measured.…”

Section: Introductionmentioning

confidence: 99%

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Sensorless Control of Dual-Active-Bridge Converter with Reduced-Order Proportional-Integral Observer

et al. 2018

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When controlling a Dual-Active-Bridge (DAB) DC/DC converter, the high frequency terminal current is usually measured for use in the current feedback controller. In order to measure that current, a wide bandwidth sensor accompanied with high-speed amplifiers are required. Furthermore, a high Analog-to-Digital sampling rate is also necessary for sampling and processing the measured data. To avoid those expensive requirements, this paper proposes an alternative control method for the DAB converter. In the proposed method, the terminal current is estimated by a reduced-order proportional integral observer. A technique is also proposed to reduce the phase drift effect when the voltages at two terminals are not matched. Afterwards, a combined current feedforward-voltage feedback control system is developed to enhance the system dynamics and to regulate the output voltage. This control system needs only the information of the terminal voltages and no current sensor is required. Experimental results show that the observer can estimate the terminal current very quickly with the accuracy of more than 98%. In addition, the output voltage is well regulated with a fluctuation of less than ±2.6% and a settling time of less than 6.5 ms in the presence of a 30% load change.

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High-Frequency-Link DC Transformer Based on Switched Capacitor for Medium-Voltage DC Power Distribution Application

Cited by 131 publications

References 26 publications

An Isolated Resonant Mode Modular Converter With Flexible Modulation and Variety of Configurations for MVDC Application

An Isolated Resonant Mode Modular Converter With Flexible Modulation and Variety of Configurations for MVDC Application

Nanocrystalline and Silicon Steel Medium-Frequency Transformers Applied to DC-DC Converters: Analysis and Experimental Comparison

Sensorless Control of Dual-Active-Bridge Converter with Reduced-Order Proportional-Integral Observer

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