共查询到19条相似文献,搜索用时 837 毫秒
1.
2.
小电流接地系统广泛应用于我国35KV及以下的配电网中,由于单相接地故障的复杂性,接地电流存在着大量高频谐波。不同于常规的利用傅立叶变换分离出基波和谐波,本文采用自适应陷波滤波器对故障信号进行分析,提取线路零序电流的5次谐波分量,利用故障线路的相位与非故障线路的相位相反,幅值是所有非故障线路幅值之和这个特征进行接地故障选线,以改善小电流接地系统中非稳定电弧接地故障选线的效果。 相似文献
3.
电力系统的中性点接地方式是一个综合性的技术问题,选择不同的接地方式,对电力系统建设和运行的安全性、可靠性和经济性有着重要的意义.本文针对配电网采用的不接地、经消弧线圈接地两种方式下发生单相接地故障时,短路电流较小导致选线困难的问题进行分析,利用零序电流比较法和五次谐波法进行分析,研究故障的识别与定位. 相似文献
4.
5.
中性点谐振接地能够减小单相接地故障时流经故障点的电流,从而使电弧瞬时熄灭,这不仅对电气设备和线路起到了一定的保护作用,而且还进一步提高了供电可靠性。然而,在单相接地故障电流受到限制后,故障线路与正常线路并没有差别,这给故障线路的选线带来了一定的困难。基于此点,文中首先对谐振系统单相接地故障的类型和现象进行分析,并在此基础上对并联电阻选线的优化进行研究。 相似文献
6.
逆变电源在配电系统中发挥着至关重要的作用,通过在逆变电源中加入消弧线圈,可以在单相接地发生故障时及时给系统增加电流补偿并甄别故障线路。研究针对这种带消弧选线功能的三相四线逆变器结构进行仿真测试,根据系统各个电气参数变化的测试结果,发现本结构结合功率前馈无差拍的控制方法,可有效解决配电网发生单相接地故障时排查难等问题,试验结果同时验证了不接地系统带消弧选线功能的并网逆变器在配电系统发生故障时会向系统提供能量,起到消弧和选线的作用 相似文献
7.
8.
由于传统技术在配电网单相接地故障选线中应用效果不佳,不仅选线正确率比较低,而且选线耗时比较长,无法达到预期的故障选线效果,为此提出5G通信环境下基于注意力机制的配电网单相接地故障选线技术。在5G通信环境下利用信号感知器拾取配电网线路暂态量信号,并对感知信号双边滤波处理,通过对暂态量信号S变换,提取到配电网线路故障信号时频特征,利用注意力机制选择单相接地故障线路,以此完成5G通信环境下基于注意力机制的配电网单相接地故障选线。经实验证明,设计技术选线正确率在95%以上,选线耗时在1s以内,在配电网单相接地故障选线方面具有良好的应用前景。 相似文献
9.
10.
分析了小电流接地系统单相接地运行时几种易出现的故障,阐述了接地故障的判别方法及对策,并在此基础上研究了小电流接地系统单相接地的选线方案.实验证明,该系统可准确地对单项接地故障进行确认并报警. 相似文献
11.
12.
13.
This paper describes a line-interactive single-phase to three-phase converter. A typical application is in rural areas supplied by a single-wire with earth return system. The traditional objective of feeding a three-phase induction motor is not anymore the main concern for such conversion. Due to the evolution of the farm technology, some of the local loads (as electronic power converters, computers, communication equipments, etc) require high power quality that is intended as sinusoidal, symmetrical, and balanced three-phase voltage. Additionally, to maximize the power from the feeder, the system provides a unity power factor to the grid. A three-phase voltage source inverter-pulsewidth modulation converter is used for this purpose. The power converter processes a fraction of the load power and the energy necessary to regulate the dc link voltage. As it does not need to supply active power, it is not necessary to have a source at the dc side. However, if island mode operation is needed, a dc source must be available at the dc link to supply the load. The control strategy, design criteria, and experimental results are presented 相似文献
14.
A new multilevel PWM method: a theoretical analysis 总被引:24,自引:0,他引:24
Carrara G. Gardella S. Marchesoni M. Salutari R. Sciutto G. 《Power Electronics, IEEE Transactions on》1992,7(3):497-505
Generalization of the pulsewidth modulation (PWM) subharmonic method to control single-phase or three-phase multilevel voltage source inverters (VSI) is considered. An analytical expression of the spectral components of the output waveforms covering all the operating conditions is derived. The analysis is based on an extension of Bennet's method. The improvements in harmonic spectrum are pointed out, and several examples are presented, which prove the validity of the multilevel modulation 相似文献
15.
16.
为了实现太赫兹气体频谱分析传感器,对245 GHz次谐波接收机芯片的片外测试展开研究。建立了245 GHz次谐波接收机片外测试系统以及基于245 GHz接收机芯片及发射机芯片的气体频谱分析传感器片外展示测试系统,对245 GHz次谐波接收机芯片转换增益和带宽进行测试。片外测试系统得到15 dB转换增益和15 GHz带宽;片外展示测试系统得到9 dB转换增益和16 GHz带宽。片外测试系统和片外展示测试系统结果基本吻合。在片外展示测试系统中加入气腔,即构成气体频谱分析传感器。与现有同类型传感器相比,本文的次谐波接收机具有高增益、高带宽、集成本地振荡信号、低功耗等优势,非常适用于消费电子领域小体积的智能气体频谱分析传感器。 相似文献
17.
Klaus G. Johannsen 《International Journal of Satellite Communications and Networking》1995,13(6):453-471
Several future operators of the mobile handheld telephone (P-service) satellite communications systems are gearing up for system implementation to compete for the mobile handheld telephone market of the future. While these companies are proceeding with system realization, they are also looking for partners to finance these huge satellite projects. Potential partners or bulk users are administrations of national communication systems and operators of national communication satellites. These future partners ask themselves which P-service satellite communication system they should choose. There is not an easy answer because P-service satellite systems come in many varieties. There are the low altitude earth orbiting satellites (LEOs), the medium altitude earth orbiting satellites (MEOs), and the geosynchronous altitude earth orbiting satellites (GEOs). Each system has a different type of satellite repeater: digital regenerative, transparent digital, and the bent-pipe. And each satellite system uses its own modulation/multiple access system. The fact that satellites circle the earth at different altitudes has an impact on speech quality, and, because systems vary in satellite as well as constellation complexity, there are different price tags attached. All systems display ingenious features and will eventually work. Mobile users will decide which system will best serve their purposes. This article attempts to compare six P-service satellite systems and find a method for system selection. By use of self-established system criteria, it is possible to arrive at a P-service system selection. By weighing the system criteria, the sensitivity of system selection can be tested. The results or the selection of a particular system should not be considered a recommendation; rather, the process of selection should be used as a possible guideline. 相似文献
18.
19.
Sanchez F. LeFlohic M. Stephan G.M. LeBoudec P. Francois P.-L. 《Quantum Electronics, IEEE Journal of》1995,31(3):481-488
We present experimental evidence of quasiperiodic route to chaos in erbium-doped fiber laser operating simultaneously at 1.550 μm and 1.536 μm. Starting from a CW state for high pumping rates the system becomes T-periodic, 2T-periodic, 3T-periodic and chaotic for decreasing pumping ratios. The low-frequency spectra shows two fundamental frequencies. The nT-periodic regimes correspond to a frequency locking of the low frequency on a subharmonic of the high frequency. An adapted model based on the rate equations is numerically investigated and leads to a good qualitative agreement with the experimental data 相似文献