排序方式: 共有12条查询结果,搜索用时 15 毫秒
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中压直流配电网与直流负荷、直流微电网的互联是实现直流配电网的关键,这将迫切需要一种适应于中压和低压大跨度变比的直流变压器(即DC/DC换流器)。三相双主动全桥(dual-active bridge,DAB)换流器具备可隔离、可实现双向功率流动、滤波器体积小等优点,该文基于三相DAB换流器拓扑,结合中压直流配电网DC/DC换流器高压侧电压应力大、低压侧电流应力大等特性,设计了一种基于三电平方式的DC/DC换流器模块,进而采用输入串联、输出并联的模块化级联方式设计了中压直流配网DC/DC换流器。最后,提出了换流器模块高、低压侧协调控制方式以及模块化DC/DC换流器的输入电压均分、输出电流均分控制方式,并在MATLAB/Simulink里验证了其可行性。 相似文献
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交流微电网和直流微电网之间多通过电力电子变压器(PET)构成交直流混合微电网以减少额外的电能转换环节。但是PET中高频变压器的谐振参数常常限值了效率的提升,且谐振拓扑的细微变化也会进一步加剧参数设计的难度。针对该问题,提出一种面向交直流混合微电网(HADM)的双向谐振型高频直流变压器(HFT)通用型参数设计方法,明确只有在谐振电流与输入方波电压基频部分同频同相时传输的平均功率最高。并指出当变压器励磁电感与漏感之比大于一定值时,CLLC、LLC和CLL谐振型高频变压器均可工作在双向功率传输状态,且获得的标幺化增益和效率均满足HADM系统要求,CLLC更有利于功率的有效传输。最后,搭建了一台采用SiC器件的6 kW实验样机,实验结果进一步验证了所提设计方法的可行性和有效性。该样机在双向工作模式下的最高效率大于97%。 相似文献
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af Wåhlberg AE 《Accident; analysis and prevention》2003,35(4):473-486
The paper discusses some methodological problems in (psychological) research on traffic accident predictors and reviews a convenience sample of the literature. Three methodological aspects are identified as being important: reliability of accident predictors, time period for accidents used as dependent variable, and culpability for accidents. Papers are scrutinized and most are found to be wanting in these aspects. Traffic researchers do not adhere to, or hardly even discuss, these basic methodological problems. It is concluded that the current research into (psychological) accident predictors is fraught with methodological deficiencies. Why most studies seem to be deficient in these aspects is not clear, as several researchers have pointed out these problems. 相似文献
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本文系统论述了分数傅立叶变换在信号处理中的两个典型应用:信号滤波和信号分离;提出了分数傅立叶滤波器的设计思想和用分数傅立叶变换的特殊形式半傅立叶变换实现信号的分离的算法实现.通过MATLAB仿真实验证实:分数傅立叶滤波的效果明显优于傅立叶滤波;半傅立叶变换可以有效地从遥感探测早期响应的减幅正弦波的衰减指数中分离出似脉冲分量,进而去确定被探测物体的固有谐振频率. 相似文献
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Hydrates always are considered as a threat to petroleum industry due to the operational problems it can cause.These problems could result in reducing production performance or even production stoppage for a long time.In this paper,we were intended to develop a LSSVM algorithm for prognosticating hydrate formation temperature (HFT) in a wide range of natural gas mixtures.A total number of 279 experimental data points were extracted from open literature to develop the LSSVM.The input parameters were chosen based on the hydrate structure that each gas species form.The modeling resulted in a robust algorithm with the squared correlation coefficients (R2) of 0.9918.Aside from the excellent statistical parameters of the model,comparing proposed LSSVM with some of conventional correlations showed its supremacy,particularly in the case of sour gases with high H2S concentrations,where the model surpasses all correlations and existing thermodynamic models.For detection of the probable doubtful experimental data,and applicability of the model,the Leverage statistical approach was performed on the data sets.This algorithm showed that the proposed LSSVM model is statistically valid for HFT prediction and almost all the data points are in the applicability domain of the model. 相似文献
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针对显著性目标检测在复杂背景下准确率低的问题,提出超复数傅里叶变换改进的条件随机场显著性目标检测方法。首先,建立图像无向图并提取节点特征;然后重构超复数傅里叶变换得到平滑振幅谱与相位谱,获得无向图节点背景抑制权值,从而初步确定多尺度高斯核背景抑制图;最后输入到训练后的条件随机场中,通过增强目标表示得到最终显著性目标区域。实验表明,本文方法在准确率上较现有流行方法有显著提高,且能够在抑制复杂背景的同时,准确锁定指定目标位置区域。实验验证本文方法在复杂背景下显著性目标检测具有较好的准确性和鲁棒性。 相似文献
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双有源桥(DAB)DC-DC变换器中的高频隔离变压器是电能路由器的核心器件之一,在整个系统中承担着电气隔离、电压变换和功率双向传输的功能,对高频隔离变压器的漏感参数进行精确提取具有重要意义。而基于传统变压器实验的漏感测量方法不能很好地匹配变压器的实际工作波形,为此,提出一种基于DAB移相控制实验的提取漏感方法。基于该方法,在不同的工作频率和电压条件下,对待测变压器进行了多组实验,实验结果证明了该方法的有效性。最后分析总结了变压器漏感和工作频率、电压幅值、移相比等因素的变化关系。 相似文献
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祝敬辉 《仪器仪表标准化与计量》2010,(4):25-27,30
在SIS设计中,可用性和安全性是两个非常重要的概念。那么何为可用性,何为安全性?它们关注的重点分别是什么,两者之间有什么内在的联系?笔者试图通过对IEC 61508和IEC 61511的解读,剖析这两个重要原则是如何在SIS设计中实现的。 相似文献
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