The diode rectifier unit(DRU)-based high-voltage DC(DRU-HVDC) system is a promising solution for offshore wind energy transmission thanks to its compact design, high efficiency, and strong reliability. Herein we inves...The diode rectifier unit(DRU)-based high-voltage DC(DRU-HVDC) system is a promising solution for offshore wind energy transmission thanks to its compact design, high efficiency, and strong reliability. Herein we investigate the feasibility of the DRU-HVDC system considering onshore and offshore AC grid faults, DC cable faults, and internal DRU faults. To ensure safe operation during the faults, the wind turbine(WT) converters are designed to operate in either current-limiting or voltage-limiting mode to limit potential excessive overcurrent or overvoltage. Strategies for providing fault currents using WT converters during offshore AC faults to enable offshore overcurrent and differential fault protection are investigated. The DRU-HVDC system is robust against various faults, and it can automatically restore power transmission after fault isolation. Simulation results confirm the system performance under various fault conditions.展开更多
Houshiheisan is composed of wind-dispelling （chrysanthemun fower, divaricate saposhnikovia root, Manchurian wild ginger, cassia twig, Szechwan lovage rhizome, and platycodon root） and deficiency-nourishing （ginseng...Houshiheisan is composed of wind-dispelling （chrysanthemun fower, divaricate saposhnikovia root, Manchurian wild ginger, cassia twig, Szechwan lovage rhizome, and platycodon root） and deficiency-nourishing （ginseng, Chinese angelica, large-head atractylodes rhizome, Indian bread, and zingiber） drugs. In this study, we assumed these drugs have protective effects against cerebral ischemia, on neurovascular units. Houshiheisan was intragastrically administered in a rat model of focal cerebral ischemia. Hematoxylin-eosin staining, transmission electron microscopy, immu- nofluorescence staining, and western blot assays showed that Houshiheisan reduced pathological injury to the ischemic penumbra, protected neurovascular units, visibly up-regtflated neuronal nuclear antigen expression, and down-regulated amyloid precursor protein and amyloid-[3 42 expression. Wind-dispelling and deficiency-nourishing drugs maintained NeuN expression to varying degrees, but did not affect amyloid precursor protein or amyloid-~ 42 expression in the ischemic penumbra. Our results suggest that the compound prescription Houshiheisan effectively suppresses abnormal amyloid precursor protein accumulation, reduces amyloid substance depo- sition, maintains stabilization of the internal environment of neurovascular units, and minimizes injury to neurovascular units in the ischemic penumbra.展开更多
远海风电场具有更加丰富和稳定的风能资源,是未来风电发展的主要趋势,目前远海风电主要通过柔性直流系统并网。整流侧采用二极管不控整流单元(diode rectifier unit, DRU)具有明显的经济优势和发展前景,是学术界和工业界的研究热点。为...远海风电场具有更加丰富和稳定的风能资源,是未来风电发展的主要趋势,目前远海风电主要通过柔性直流系统并网。整流侧采用二极管不控整流单元(diode rectifier unit, DRU)具有明显的经济优势和发展前景,是学术界和工业界的研究热点。为了进一步提高远海风电送出系统的经济性,以整流侧采用DRU的高压直流输电系统为基本拓扑,提出采用中频不控整流直流系统的远海风电送出方案,通过把风电场交流电网的运行频率选为100~400 Hz,可以大幅度减小升压变压器和交流滤波器的体积和重量。同时,提出适用于中频不控整流直流系统的风电机组控制策略,其中,机侧换流器采用定直流电压控制,网侧换流器在全局统一参考坐标系下同时实现定功率控制和定交流侧电压控制。最后,通过PSCAD/EMTDC进行算例仿真,对所提方案的可行性进行验证。展开更多
基金supported in part by the European Union’s Horizon 2020 research and innovation program under grant agreement No.691714
文摘The diode rectifier unit(DRU)-based high-voltage DC(DRU-HVDC) system is a promising solution for offshore wind energy transmission thanks to its compact design, high efficiency, and strong reliability. Herein we investigate the feasibility of the DRU-HVDC system considering onshore and offshore AC grid faults, DC cable faults, and internal DRU faults. To ensure safe operation during the faults, the wind turbine(WT) converters are designed to operate in either current-limiting or voltage-limiting mode to limit potential excessive overcurrent or overvoltage. Strategies for providing fault currents using WT converters during offshore AC faults to enable offshore overcurrent and differential fault protection are investigated. The DRU-HVDC system is robust against various faults, and it can automatically restore power transmission after fault isolation. Simulation results confirm the system performance under various fault conditions.
基金supported by the National Natural Science Foundation of China,No.30973782,81373526the Natural Science Foundation of Beijing,No.7102014,7122018the Beijing Municipal Higher Learning Institution Talent Teaching Plan"Young and Middle-aged Talented People Training"Project,No.PXM2011014226
文摘Houshiheisan is composed of wind-dispelling （chrysanthemun fower, divaricate saposhnikovia root, Manchurian wild ginger, cassia twig, Szechwan lovage rhizome, and platycodon root） and deficiency-nourishing （ginseng, Chinese angelica, large-head atractylodes rhizome, Indian bread, and zingiber） drugs. In this study, we assumed these drugs have protective effects against cerebral ischemia, on neurovascular units. Houshiheisan was intragastrically administered in a rat model of focal cerebral ischemia. Hematoxylin-eosin staining, transmission electron microscopy, immu- nofluorescence staining, and western blot assays showed that Houshiheisan reduced pathological injury to the ischemic penumbra, protected neurovascular units, visibly up-regtflated neuronal nuclear antigen expression, and down-regulated amyloid precursor protein and amyloid-[3 42 expression. Wind-dispelling and deficiency-nourishing drugs maintained NeuN expression to varying degrees, but did not affect amyloid precursor protein or amyloid-~ 42 expression in the ischemic penumbra. Our results suggest that the compound prescription Houshiheisan effectively suppresses abnormal amyloid precursor protein accumulation, reduces amyloid substance depo- sition, maintains stabilization of the internal environment of neurovascular units, and minimizes injury to neurovascular units in the ischemic penumbra.
文摘远海风电场具有更加丰富和稳定的风能资源,是未来风电发展的主要趋势,目前远海风电主要通过柔性直流系统并网。整流侧采用二极管不控整流单元(diode rectifier unit, DRU)具有明显的经济优势和发展前景,是学术界和工业界的研究热点。为了进一步提高远海风电送出系统的经济性,以整流侧采用DRU的高压直流输电系统为基本拓扑,提出采用中频不控整流直流系统的远海风电送出方案,通过把风电场交流电网的运行频率选为100~400 Hz,可以大幅度减小升压变压器和交流滤波器的体积和重量。同时,提出适用于中频不控整流直流系统的风电机组控制策略,其中,机侧换流器采用定直流电压控制,网侧换流器在全局统一参考坐标系下同时实现定功率控制和定交流侧电压控制。最后,通过PSCAD/EMTDC进行算例仿真,对所提方案的可行性进行验证。
