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间谐波导致的闪变特征及闪变限制曲线 总被引:2,自引:0,他引:2
电力系统中广泛使用的变频装置产生的间谐波导致了不容忽视的电能质量问题--电压闪变。依据白炽灯热平衡方程,对含间谐波电压作用下白炽灯输出光通量的时变波形进行了理论分析。研究表明,高、低频间谐波电压都可能造成白炽灯闪变,且间谐波幅值和频率、与间谐波最靠近的谐波次数及其奇偶性都是影响光通量波动频率和波动深度的因素。基于IEC闪变仪标准和光通量波动特征与电压间谐波分量参数的关系,提出了间谐波的闪变限制曲线。 相似文献
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The application of variable-frequency drives (VFDs) in industrial and commercial facilities has seen a tremendous increase. However, when multiple VFDs are fed from one dedicated power transformer, care should be taken not to drive the transformer into saturation. At one industrial location, nine VFDs rated at 200 HP each, and fed from a single 1500 kVA air-cooled transformer, showed saturation phenomenon, which had the potential of causing serious damage to the transformer. This paper discusses the input AC current waveform asymmetry caused by the interaction of the transformer and the nine 200 HP VFD load fed from it. The term waveform asymmetry is used when the positive half of the input AC current cycle is not equal to the negative half of the input AC current cycle. This results in the existence of DC components along with even harmonics in the input at current waveform. The various tests and the eventual solution to the waveform asymmetry caused by the VFDs is presented. The value of the inductance in the DC smoothing inductor (DC-link choke), which is included as part of the VFD, was found to contribute significantly to the waveform asymmetry. Experimental results showing the performance of a reconfigured DC-link inductor to reduce its interaction with the power transformer are presented 相似文献
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宽频量测技术的快速发展为部分新能源发电并网节点的次/超同步振荡监测提供了有效手段,但是由于测量单元布点限制,难以获得全网的振荡传播和分布。为此,提出了一种基于新能源发电并网点宽频量测间谐波潮流计算的次/超同步振荡溯源方法。给出了次同步振荡频率下间谐波潮流算法的网络模型和元件模型,总结了间谐波潮流计算的详细步骤,通过间谐波潮流计算可得到各个节点的间谐波电压电流分布,进而获得全网次/超同步振荡传播路径。当新能源发电系统次同步振荡传播引发邻近火电机组轴系扭振时,存在扭振机组间谐波等效阻抗突变的特性,从而造成间谐波潮流分布发生变化,根据预想振荡状态下间谐波潮流计算结果与实际宽频量测结果间的不同,可用于新能源发电次同步振荡引发邻近火电机组轴系扭振的溯源定位。最后,基于四机两区域系统和IEEE 10机39节点系统算例验证了所提方法的有效性和准确性。 相似文献
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Phase sequence is an important attribute of voltages and currents in three phase power systems. This paper investigates the sequence characteristics of interharmonic components. Three common cases involving interharmonics are analyzed. These are variable frequency drives (VFD), motors with fluctuating mechanical loads and general fluctuating impedance loads. The results reveal that interharmonics can have either positive or negative sequence and are rarely zero sequence. Its sequence cannot be determined by examining the interharmonic frequency alone. The general rule is that the sequence of interharmonics is the same as that of the supply system harmonic components being modulated. If the resulting interharmonic frequency produced by the modulation process is negative, the sequence of the interharmonic component will change from positive to negative or vice versa. The findings of this paper will help to improve our understandings on the characteristics of interharmonics and can be useful for the development of interharmonic simulation programs. 相似文献
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论述了间谐波检测装置的研制,介绍了间谐波检测算法(迭代DFT算法)的优点、硬∕软件设计流程、装置的校验方法及实验结果;提出了"间谐波记录"这一概念,有利于衡量电力系统中间谐波的含量。对3种典型间谐波源进行了间谐波的实际测量工作;分析了间谐波的测量结果,指出由于3个测量点所带的间谐波源负荷不同,所监测到的间谐波成分也各有特点。根据测量结果,指出了IEC61000系列标准在应用中存在的缺陷;并且建议,中国的间谐波标准应该按4个频率段的划分来取不同的间谐波限值。 相似文献
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基于贪心算法的自适应解列断面自动搜索方法:(一)解列指标体系与算法设计 总被引:1,自引:0,他引:1
现有的解列断面搜索方法仅能考虑发电机同调、孤岛功率平衡等少数约束条件,在大系统的解列断面搜索过程中需要事先人工化简系统,无法实现从在线调度数据出发自动获得解列断面。文中以交直流系统的自适应解列控制为研究目标,提出了交直流电网解列指标体系,并设计了基于贪心算法的解列断面自动搜索方法。该方法根据系统发电机慢同调分群结果,确定解列孤岛数量及孤岛初始搜索节点,然后,对各孤岛一级相连节点进行评分,确定应该并入各孤岛的节点;最后,设计了解列策略校验环节。 相似文献
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介绍了驱动往复式压缩机用单支撑电机轴系挠度和临界转速的相关计算,并给出了计算实例,同时对轴的强度计算做了简要介绍。由于该电动机的负载特性决定了在轴系设计时要综合考虑刚度和强度,同时应与压缩机轴系共同做扭振分析,保证整个轴系固有扭振频率避开强制振荡频率,避免发生共振,以确保电机运行可靠性,提高机组系统安全。 相似文献
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常见电压暂降类型包括三相暂降、两相暂降和单相暂降,不同类型的暂降对变频器的影响程度有较大的不同,需要研究能够代表变频器在不同类型暂降下的耐受特性的统一规范。文中通过机理分析、仿真和试验研究,给出了变频器在不同暂降类型下具有一定代表性的通用耐受曲线包络线。分析了变频器受不同类型暂降的影响机理,并在MATLAB/Simulink环境下搭建仿真模型进行验证;搭建了试验平台,选取国内市场具有代表性的7种品牌、2种功率(7.5 k W和18.5 k W)的8台变频器进行测试,与理论分析和仿真研究进行相互验证,其结论基本一致。通过对试验结果的处理,得到了变频器在额定转矩转速时不同暂降类型下的通用耐受曲线包络线,具有实际应用价值,可为变频器耐受曲线标准的制定提供重要参考。 相似文献
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含多种分布式电源的微网动态仿真 总被引:27,自引:12,他引:15
通过算例仿真研究了不同分布式电源配置方案下低压微网从并网模式向孤网模式转换的动态运行特性,获得了分布式电源的功率、微网电压和频率的变化规律。如果选择微型燃气轮机作为微网的功率支撑手段,在微网从并网向孤网过渡过程中,系统频率波动较大,且部分分布式电源有可能在低频保护动作下与电网隔离,不利于微网的稳定运行;增加储能设备后,储能设备对于微网的稳定运行可发挥重要的作用。采用下垂控制策略的蓄电池在微网孤岛运行时可以快速为系统提供有功、无功支撑,有效抑制了由于燃气轮机动态响应速度慢引起的电压和频率偏差。 相似文献
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This paper describes a damping control method of power converters for suppression of resonance in DC power network. The resonance occurs when a resonant frequency of the DC distribution line coincides with the frequency of the harmonic or interharmonic components generated by the power converters. For detailed investigation, a combined system which consists of a pulse‐width modulated (PWM) rectifier and a PWM inverter is treated as the simplest example. To suppress the resonance, a DC‐side damping control method is proposed and its implementation and design method are discussed in detail. Then, the proposed damping control method is applied to the combined system of a PWM rectifier and a PWM inverter. Experimental results verify the validity and practicability of the proposed damping control method. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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Lockley W.E. Driscoll T.S. Wharran W.H. Paes R.H. 《Industry Applications, IEEE Transactions on》1995,31(6):1412-1418
This paper discusses the causes and effects of torsional harmonics in adjustable frequency induction motor drives, describes some electrical and mechanical methods used to mitigate potentially harmful effects, describes methods of predicting torsional harmonic levels, describes methods of measurement of torsional harmonics, and compares the measured and predicted levels for a particular 6000-HP centrifugal compressor application at the Shell Hamburg Gas Plant, Alabama, using a PWM CSI induction motor drive 相似文献
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Variable-speed AC drives have a well-founded reputation for versatility and dependability, with many features and benefits that are just not available from other drive technologies. They are presently used in applications ranging from simple fan control to complex operations including process loops, positioning and indexing, and industrial laundry applications. The author briefly discusses variable frequency drives (VFD) theory and pulse width modulation. The author then describes a cost-effective VFD which is available for use on commercial laundry machines. It offers the latest in IGBT technology, the application-specific intelligent power module (ASIPM). This module eliminates control components normally associated with transistor firing schemes. All components are embedded in the ASIPM module. It can be used with both singleand three-phase input power, and voltages from 190 to 480 V. Control logic is stored in one application-specific IC and is user-addressable to allow programming for special requirements. Wash formulas, unbalance detection, and cycle times can all be programmed directly into the VFD software, eliminating the need for timers, microprocessors, etc 相似文献
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Pulsating Torques in PWM Multi-Megawatt Drives for Torsional Analysis of Large Shafts 总被引:1,自引:0,他引:1
Song-Manguelle J. Nyobe-Yome J.-M. Ekemb G. 《Industry Applications, IEEE Transactions on》2010,46(1):130-138
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间谐波相序特性的研究 总被引:10,自引:0,他引:10
相序是三相电力系统中电压和电流的重要特性。为了认识间谐波的相序特性,文中以两种典型的间谐波源(变频驱动装置和电动机)为例,通过理论分析和实验探讨了它们产生的间谐波的相序。研究表明间谐波可以表现为正序或负序。但是间谐波的相序特性不同于谐波,同一频率的间谐波可以具有不同的相序。一般规律是:间谐波的相序与被调制的系统基波(或谐波)分量的相序相同。如果调制后得到的频率为负值,则间谐波信号的相序将变反,即由正序变负序或由负序变正序。文中的研究成果有助于深入认识间谐波的特性和发展间谐波仿真软件。 相似文献
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A. Sheela S. Vijayachitra S. Revathi 《IEEJ Transactions on Electrical and Electronic Engineering》2015,10(5):503-511
This paper presents a study on a grid‐connected and islanded multiple distributed generation (DG) system for frequency and voltage regulation. The multiple DG system includes solar cells, wind turbine, fuel cell, and battery storage. The H‐infinity controller is used whose weighting parameters are optimized to minimize voltage and frequency deviation. The performance of the system is analyzed under different conditions for both grid‐connected and islanded modes of operation. In case of the load variations, the inner voltage and current loop react based on the H‐ infinity control strategies. The outer power loop uses the droop characteristic controller. The design is simulated using MATLAB/SIMULINK. The simulation results show that the multiple DG system can supply high‐quality power both in grid‐connected and islanded modes. Also, we show that the proposed control methodology will make the system to transit smoothly between the islanded mode and the grid‐connected mode. The results indicate that the frequency and voltage deviations meet the nominal values as per IEEE standard. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献