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1.
分析了联络线风电侧距离保护测量阻抗随风速、过渡电阻等参数变化时的特性。基于双馈异步(DFIG)、普通异步(IG)机组仿真了线路不同故障下改变风速、过渡电阻等参数时距离保护测量阻抗的变化。结果表明,由于对侧电源的助增和本侧风机风速变化使过渡电阻呈电容性或电感性,可引起距离保护保护范围缩短或使保护装置超范围动作,从而导致保护产生误动或拒动。针对测量阻抗随过渡电阻变化的特性,提出了相应的改进措施。  相似文献   
2.
To reduce the parallel transient and resume the power balance immediately after fault clearing, many countries have included the low voltage ride through (LVRT) requirements in the grid codes for grid-connected wind turbines (WTs). Although the removal of the WT from the power grid in the conventional approach is beneficial to alleviate severe mechanical stress incurred by the low voltage fault, remaining the WT to be connected to the grid during the low voltage fault becomes obligate to reduce the risk of voltage collapse for the power system associated with the ever-increasing WT installation. This article presents a control strategy to which the LVRT capability enhancement of a wind-driven squirrel cage induction generator (IG) by the use of a dynamic voltage restorer (DVR). The DVR, with the flexibility of changing output voltage polarity in series with the power source, can sustain the excitation of IG subjected to the low voltage fault and the random change in load and wind speed. A DC voltage regulator is employed to support the DC-link voltage of the DVR for generating appropriate AC voltage level required for the IG. The AC output voltage of the DVR is controlled by an AC voltage regulator according to the IG terminal voltage deviation from the desired value. To achieve voltage and current decoupling control between distinct coordinate axes in the stationary reference frame, a proportional-resonant (PR) controller is adopted. The DVR output voltage can be instantaneously tracked by the PR controller according to the sinusoidal command comes from the DC and AC regulators. To fully utilize the compensation capacity for the DVR, the dynamic estimation of grid voltage lower limit for recasting the AC voltage command (ACC) of the DVR in response to the low voltage fault is proposed to prevent DVR from malfunction due to controller saturation. The experimental results confirm the effectiveness of the proposed strategy.  相似文献   
3.
This paper presents a comparative study of reactive power control for isolated wind-diesel hybrid power system in three different cases with wind power generation by induction generator (IG), permanent-magnet induction generator (PMIG) and permanent-magnet synchronous generator. The synchronous generator (SG) is used with diesel engine set. A mathematical model of the system based on small signal analysis, is developed considering reactive power flow balance equations. The variable reactive power needed by the system is provided by a static synchronous compensator (STATCOM) when wind power generation is done by IG and PMIG. When permanent-magnet synchronous generator (PMSG) is used for wind power generation, the variable reactive power demand is fulfilled by a voltage source converter (VSC) which is on the load side. A new mathematical approximation model for VSC connected with PMSG is proposed such that the voltage source converter fulfills the increased reactive power requirement of load and also increases its active power equal to the increased input wind power. Proportional and integral (PI) gains of the STATCOM and VSC controllers are optimized using integral square error criterion (ISE). The dynamic responses of the system for small (1%) step increase in load reactive power with and without 1% step increase in input wind power are shown. The paper also shows the dynamic responses of the system for random step change in load reactive power plus random step change in input wind power. The MATLAB/SIMULINK environment is used for simulation.  相似文献   
4.
宋月红 《山西建筑》2009,35(18):160-161
通过细水雾灭火系统在聊城大学演播厅中的应用,介绍了细水雾灭火系统的组成,对细水雾灭火系统与IG541灭火系统的性价比进行了分析,强调了细水雾灭火系统在施工、使用中应注意的问题,从而促进绿色消防技术的发展。  相似文献   
5.
王斌  段立业 《玻璃》2008,35(1):45-47
回顾了中空玻璃在北美洲的发展历史以及现在主流技术和工艺,并对应进行了客观的分析.借此机会,希望把国外中空玻璃的发展历程和先进工艺技术介绍到中国,以期对中国业者把握中空玻璃技术和工艺的趋势有所帮助,并按所求对制造工艺及材料做出正确选择.  相似文献   
6.
本文通过变频装置在瑞士HASLER公司生产的电子称量料机上的应用,详细介绍了其变频调速的设计原理、控制过程和性能参数。对今后实际工作中,应用变频器调速对旧设备进行改造有一定的帮助。  相似文献   
7.
A new Y-based liquid source, composed of Y2O3, BaCuO2, and CuO, was prepared and used to fabricate large Gd-Ba-Cu-O (GdBCO) single domains of 30 mm in diameter by the infiltration and growth (IG) process. After detailed investigations in the morphology, microstructure, and superconducting property of the grown sample, it was found that, the proposed Y-based liquid source can be used to fabricate well-textured large GdBCO single domains, and can also increase the utilization rate of the liquid source powder. Additionally, employing our method can simplify the IG process and advance the experimental efficiency because only two precursor powders, involving Gd2BaCuO5 and BaCuO2, are needed to prepare for the whole process flow.  相似文献   
8.
掺油中空玻璃密封胶的性能评价   总被引:1,自引:0,他引:1  
通过对比实验,比较了掺油和未掺油中空玻璃密封胶的耐久性、热老化性能、粘接性能以及与热熔丁基密封胶的相容性,比较了其制造的中空玻璃的耐紫外辐照性能.深入分析了掺油中空玻璃密封胶所带来的一系列严重的质量问题及其在使用过程中的危害性.  相似文献   
9.
In this paper, we propose two independent gate (IG) FinFET SRAM cells that use PMOS access transistors and back-gate (BG) biasing to achieve a high-stability performance. In the first cell, the back-gate of the access transistors is connected to the adjacent storage nodes, and the back-gate of the pull-down transistors is dynamically biased. Simulations indicate that the first proposed cell offers higher read static noise-margin (SNM), higher write-ability, least static/dynamic power, and a comparable read current compared to the previous IG-6TSRAMs. The second cell is a novel independently-controlled-gate FinFET SRAM cell, which provides a high read stability, the highest write-ability, low static power dissipation and high read current compared to the previously reported independently-controlled-gate FinFET SchmitTrigger based SRAM cells. This cell supportsbit-interleaving property at VDD = 0.4 V with high read/write yields.  相似文献   
10.
针对当前基于特征加权的模糊支持向量机(FSVM)只考虑特征权重对隶属度函数的影响,而没有考虑在样本训练过程中将特征权重应用到核函数计算中的缺陷,提出了同时考虑特征加权对隶属度函数和核函数计算的影响的模糊支持向量机算法——双重特征加权模糊支持向量机(DFW-FSVM)。首先,利用信息增益(IG)计算出每个特征的权重;然后,在原始空间中基于特征权重计算出样本到类中心的加权欧氏距离,进而应用该加权欧氏距离构造隶属度函数,并在样本训练过程中将特征权重应用到核函数的计算中;最后,根据加权的隶属度函数和核函数构造出DFW-FSVM算法。该方法避免了在计算过程中被弱相关或不相关的特征所支配。在8个UCI数据集上进行对比实验,结果显示DFW-FSVM算法的准确率和F1值较5个对比算法(SVM、FSVM、特征加权SVM(FWSVM)、特征加权FSVM(FWFSVM)、基于中心核对齐的FSVM(CKA-FSVM))中的最好结果分别提升了2.33和5.07个百分点,具有较好的分类性能。  相似文献   
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