Three Phase Harmonic Power Flow Using PhaseComponent for Asymmetric Network

With the increasement of the harmonic quantity in power system ,single phase harmonic power flow calculation can't meet the needs. This paper discusses the components model in detail under harmonic condition in three phase distribution power system, include generator,transformer,line and load. Particularly, the transformer model considers the winding connection, the phase shifting among primary and secondary windings, and the off-normal tapping.The three-phase model of transformer, used in traditional harmonic power flow, may the preuent the model from converging, so the paper proposes a three phase back forward sweep harmonic load flow algorithm based on phase-components. At last, a test example was used to prove the algorithm. The results indicate that the proposed method is efficient.     

粗纤维压缩打捆机构模态与谐响应分析

针对机械式压缩打捆机构在工作过程中因机械振动而发生疲劳失效的问题,采用模态分析理论,利用分块兰索斯法求解得到打捆压缩机构的固有频率和振型,以及偏置式曲柄滑块机构的较大形变区域。同时,提取该区域内的关键点进行谐响应分析,获得各关键点最大谐峰值及共振点的频率。其模态与谐响应分析结果表明:在压缩推进器两侧挡板、连杆中部和压缩打捆机构中的减速器动力输出曲柄与连杆铰接处最可能产生共振并发生较大形变,压缩打捆机构在116.89、130.31、508.36、621.49、750.35Hz频率时易产生共振现象。为此,提出在易发生变形的薄弱环节采取焊接加强板及增添连接螺栓等方式,避开其共振点频率,为传动方式选用和整机结构改进提供理论依据。     

基于小波去噪的加窗FFT电网谐波检测

提出一种基于小波去噪的软硬阈值改良折衷法与加布莱克曼窗的傅里叶变换算法相结合的谐波检测方法。该方法采用小波软硬阈值改良折衷法对含噪的电力谐波信号进行降噪处理,利用加布莱克曼窗的傅里叶变换算法对去噪后的信号进行分析,提取各次谐波的幅值和频率。仿真检测结果表明小波去噪后的谐波波形接近于原始信号谐波波形,信噪比提高了8.3226dB,小波去噪与FFT 结合的方法适合在谐波检测系统或装置中应用。     

Genetic diversity of nitrate reducing bacteria in marine and brackish water nitrifying bacterial consortia generated for activating nitrifying bioreactors in recirculating aquaculture systems

Nitrate reducing potency of 88 bacterial isolates segregated from marine and brackish water nitrifying bacterial consortia (NBC), generated for activation of nitrifying bioreactors, was confirmed by determining the nitrate reducing capability under aerobic conditions as maintained in nitrifying bioreactors. All the isolates had the potential to be used as bio‐augmentors for activating nitrate dissimilation in recirculating aquaculture system. The existence of nitrate reducers with nitrifiers in NBC and in the reactor configuration negates the requirement of integrating anoxic denitrifying system for effective removal of NO₃^?‐N. Phylogenetic analyses of representative isolates from each cluster of the dendrograms generated based on phenotypic characterization and amplified ribosomal DNA restriction analysis revealed profound diversity of nitrate reducing bacterial flora in the NBC. They were composed of Streptomyces enissocaesilis, Marinobacter sp., Pseudomonas sp., Microbacterium oxydans, Pelagibacterium halotolerans and Alcanivorax dieselolei from marine NBC and Streptomyces tendae, Nesterenkonia sp., Bacillus cereus, Microbacterium oxydans and Brevibacterium sp. from brackish water NBC. The diversity indices of the consortia were calculated using Mega 5.0, primer 7 and VITCOMIC softwares. Marine NBC exhibited higher Shannon wiener diversity and mean population diversity than brackish water NBC. The study delineated higher species richness and diversity in marine NBC than in its brackish water counterpart, a possible reflection of the higher biodiversity of marine systems, and hence, the former is more promising to be used as start‐up cultures for the activation of nitrifying bioreactors after appropriate acclimatization to the desired salinity.     

简谐激励下喷雾机矩形药箱内液体晃动力矩的实验研究

在液体晃动引起的横向力和倾覆力矩作用下,喷雾机本体及喷杆系统的平衡均会受到影响,进而影响行驶稳定性和施药效果.为此,以常用的矩形药箱为研究对象,以压电式力传感器为主要测量元件,设计并构建了实验系统,探讨了液体深度、激励幅值和激励频率等因素对液体晃动力矩的影响规律,并将实验结果与基于浅水波理论的线性模型进行比较.结果表明...     

基于虚拟仪器的农村小钢铁厂电压谐波检测

利用虚拟仪器LabVIEW软件设计了谐波检测平台,对农村某加工钢铁制品企业变电所的电压谐波状况进行模拟,并采用快速傅里叶方法通过加窗函数进行谐波分析,分析结果由LabVIEW的RGT工具包进行编程并生成报表,通过报表可以清晰地了解到该企业电能质量状况。     

普通圆柱蜗杆减速器的模糊可靠性优化设计

在普通优化设计的基础上，综合运用了可靠性设计和优化设计方法，并应用模糊教学理论，进行了普通圆柱蜗杆减速器的模糊可靠性优化设计．由于全面考虑了设计参数的随机性和模糊性，因而能得出更加符合实际的优化解．     

Harmonic Damage of Power Usage in Civil Building and Relevant Restraining Method

This paper introduces some common harmonic damage of power usage in civil building and analyzes some reasons for it. Then, some practical and simple restraining methods are suggested and some calculating methods are given as reference for electric engineering technicians.     

The study on Harmonic Wave Compensation Method of a SCR Regulating-Speed Control Filter Device in a Serosystem

We have studied the method of eliminating the harmonic wave of SCR regulating-speed device a servosystem and increasing its power supply unit' s loading ability when its current is large. Compared with other methods by experiment,we think the compensation method using micro-computer to auto control harmonic wave filter compensation is simpler and more practical.     

Measurement of interharmonics in power network based on all phase FFT time shifting and phase difference

The harms brought by interharmonics have attracted people’s attention more and more. The research of interharmonics is based on the actual measurement of the interharmonics in power network. An interharmonics detection method of all phase fast Fourier transform (apFFT) time shifting and phase difference is proposed in order to overcome the defects of the bigger measurement error brought by traditional FFT algorithm. By adopting apFFT algorithm and adjusting sample rate, we suppress spectrum leakage of all 0.1 times integer time harmonics including fundamental. Frequency and amplitude corrections are obtained through main spectrum line phase difference. The apFFT main spectrum lines phase values without correction are directly taken as phase values. The concept is clear and the results are direct. The algorithm has the advantage of strong anti-interference between harmonics. The simulation results show that the proposed method can detect amplitude, phase and frequency of interharmonics with high precision. The algorithm provides a new effective way for power network interharmonic detection and analysis.