As the core apparatus in dc distribution grid, the reliability of dc transformer (DCT) directly affects the safe and stable operation of the entire dc grid. Firstly, the structure and characteristics of dual active br...
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ISBN:
(纸本)9781728148786
As the core apparatus in dc distribution grid, the reliability of dc transformer (DCT) directly affects the safe and stable operation of the entire dc grid. Firstly, the structure and characteristics of dual active bridge (DAB) based dc transformer are analyzed. Then, the hierarchical reliability model of dc transformer is established by using reliability block diagram (RBD). Furthermore, based on k-out-of-n redundancy model and Markov process theory, considering module redundant number, redundancy mode and component repair rate, a detailed and comprehensive reliability evaluation model of dc transformer is proposed. Finally, based on the proposed reliability model of dc transformer, the influence of different redundancy designs and the component repair rate on the reliability of dc transformers are investigated through an example. The research results can provide a theoretical basis for redundancy design, redundancy mode selection and maintenance strategy of dc transformer, and contribute to the reliability of the whole dc grid.
The solid-state transformers with input-series output-parallel structure are considered for various applications where MVAC to LVDC conversion is needed. However, due to the inherent second harmonic pulsating power in...
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ISBN:
(纸本)9781665475396
The solid-state transformers with input-series output-parallel structure are considered for various applications where MVAC to LVDC conversion is needed. However, due to the inherent second harmonic pulsating power in the single-phase AC system, large DC link capacitors are required to smooth the voltage ripple of all floating cells, which reduces achievable power density. The active power decoupling method can shift away the pulsating power from the DC link capacitors, leading to a significant reduction to the DC link capacitance and resulting voltage ripple. So far, the application of active power decoupling is limited to single-level converters, and little research on the impact in modular converters has been done. This paper investigates the feasibility of applying active power decoupling to solid-state transformers. The active power filter with dc-split-capacitor circuit is selected to minimize the DC link capacitance. Simulation results show that the active power filter can significantly reduce the second harmonic voltage ripple and the total DC link capacitance of the SST. A prototype of the active power filter has been built and tested to verify the design.
This paper explores Dual Active Bridge Converter System (DABCS) configurations for interfacing a water electrolyzer in the MW range with a medium voltage direct current bus powered by stand-alone renewable power sourc...
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ISBN:
(纸本)9798350375596;9798350375589
This paper explores Dual Active Bridge Converter System (DABCS) configurations for interfacing a water electrolyzer in the MW range with a medium voltage direct current bus powered by stand-alone renewable power sources. The number of submodules in the DABCS varies based on the voltage and current ratings of the Insulated-Gate Bipolar Transistor (IGBT) employed. The results show that configurations with a high submodule count, enabled by low-voltage IGBT modules, exhibit superior semiconductor efficiency. However, this advantage is offset by a decrease in Medium Frequency Transformer (MFT) efficiency with an increasing number of submodules. A Pareto optimization analysis of DABCS efficiency versus power density is employed to reveal the most suitable trade-off.
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