内燃机噪声信号的独立分量分析

叙述了独立分量分析(ICA)的基本原理,分析了运用独立分量分析技术分析内燃机噪声信号的几个基本问题。单缸柴油机噪声信号峰度值的统计规律表明噪声信号满足ICA的基本要求。运用FastICA算法对某单缸机的噪声信号进行了分析,将噪声信号分解成一系列的分量。运用傅立叶变换和小波分析技术对不同的分量进行了分析,结合时频分析的结果和内燃机噪声辐射的机理确定了不同的分量与内燃机不同的噪声源相对应。     

高斯矩Fast ICA算法在风机振动信号去噪中的应用

设置了转子不平衡、联轴器不对中、风机基座松动、转子径向摩擦和轴承内圈磨损等5种故障,针对风机的振动问题进行了实验研究.在简要分析ICA理论及其算法的基础上,提出应用基于高斯矩的Fast ICA算法对模拟信号及实测离心式风机振动信号进行去噪处理,并分别与EMD及db8小波的滤波去噪效果进行定量比较.结果表明:Fast ICA方法与EMD方法和小波方法一样,能有效地处理短时瞬态及含宽带噪声的信号,但Fast ICA方法不受去噪阈值的影响,也不需要选择小波基函数,更具有通用性和稳定性.     

一种基于盲源分离和流形学习的风电机组轴承故障特征提取方法

提出一种基于盲源分离(blind source separation,BSS)和流形学习算法的风电机组轴承故障特征提取方法,首先对采集的振动信号利用独立成分分析(independent component analysis,ICA)进行盲源分离,计算各源信号的峭度和负熵,然后对源信号进行包络分析并提取上、下包络线矩阵的奇异值,将峭度、负熵和奇异值组成高维特征向量,最后利用拉普拉斯特征映射流形学习算法(Laplacian eigenmaps,LE)挖掘出高维数据中包含有效信息且具有内在规律性的低维特征。该方法充分利用并有效结合ICA在信号处理和LE在挖掘特征信息方面的优势,实现风电机组轴承故障特征的提取。算例结果表明该方法可有效提取轴承故障特征。     

基于MEEMD和KFCM的风机齿轮箱故障诊断

针对风机齿轮箱振动信号的故障特征提取与故障诊断问题,文章提出了一种基于MEEMD信号分解、样本熵和KFCM的齿轮箱故障诊断方法。首先,采用一种改进的集合经验模态分解方法(MEEMD)对采集的齿轮箱振动信号进行分解,得到了多个本征模态函数(IMF)分量;然后,计算每个IMF分量的样本熵作为齿轮箱故障诊断的特征向量;最后,使用核化的模糊聚类算法(KFCM)对齿轮箱故障样本进行聚类。通过实验数据对比表明:基于MEEMD-KFCM算法的风机齿轮箱故障诊断方法可以更加有效地识别齿轮箱故障。     

基于ICA在强背景噪声振动信号中的去噪研究

由于小波模极大值去噪方法在强背景噪声的情况下提取碰摩信号的能力变弱甚至失效,在本文中提出应用独立分量分析(ICA)方法对碰摩信号进行特征提取。通过对转子模拟实验台模拟的强背景噪声下的碰摩信号进行ICA去噪方法和小波去噪方法仿真实验,结果表明,本方法明显优于小波去噪方法,为强背景噪声下的弱振动信号的检测提供了新的途径。     

ICA在汽轮机组动静碰磨故障诊断中的应用研究

针对旋转机械振动监测和故障诊断面临的噪声干扰和多信号混杂问题,将独立分量分析法(Independent Component Analysis,简称ICA)应用到汽轮发电机组振动信号分离上,该方法可将传感器所测的混合信号分离成相互独立的单个源信号,实现对故障源的准确识别,提高故障诊断精度。对多源信号混合-分离的仿真实验,成功验证了ICA法分离混合信号的有效性。采用ICA法对某台实际机组碰磨的轴振信号进行分离,结果从机组的碰磨信号中成功分离出了代表故障的周期性冲击信号,显示出ICA法对碰磨产生的冲击信号的分离效果,实现了对碰磨故障的诊断。     

基于独立分量分析的发电机局部放电信号提取

发电机局部放电在线监测对于判断其绝缘状况意义较大,在研究发电机局部放电形成原因的基础上,研发了一套基于DSP的局放高速采集系统,提出了一种基于独立分量分析（ICA）的发电机局部放电信号提取方法,并通过实例证明了该方法的有效性。     

EEMD-RobustICA和Prony算法在电力系统低频振荡模态辨识中的应用

针对互联电网低频振荡辨识过程中Prony算法对噪声敏感的问题,该文将总体经验模态分解法、鲁棒性独立分量分析方法与Prony进行有机结合,运用到关键振荡模式辨识中。将待处理信号进行总体经验模态分解后得到的本征模态函数作为鲁棒性独立分量分析算法的输入,对得到的独立分量进行软阈值去噪后进行反变换得到重构后的本征模态函数,接着将重构后的本征模态函数相加得到去噪信号,用Prony算法对去噪信号进行辨识,最终得到低频振荡的模态参数。仿真结果表明:该方法综合利用了总体经验模态分解不依赖信号任何先验知识和完全由数据驱动的自适应性优点,及鲁棒性独立分量分析提取独立分量并保持分量信号完整性的优势,相比传统总体经验模态分解去噪算法,该方法在没有损失信号的前提下可提高分量信号的信噪比,克服Prony算法对噪声敏感的缺陷,更大程度去除噪声,有利于提高辨识精度和准确性,更能满足实际应用需求。     

微粒群算法反演粒径分布的研究

本文根据多波长下的Mie光散射理论及Lambert-Beer光透射定律,提出一种基于多相微粒群算法(PSO)反演粒子系粒径分布的有效方法.对于独立模式和非独立模式下的粒子粒径分布进行了反演计算,获得了合理的粒径分布.     

基于计算听觉场景分析的内燃机噪声源分离方法

为识别在时频域均混叠严重的内燃机燃烧噪声与活塞敲击噪声,提出并实现了基于计算听觉场景分析的内燃机噪声源分离算法.首先,对内燃机进行铅覆盖,只裸露待测部分,通过相关性分析寻找最佳测点位置,保证为分离算法提供更有效输入;其次,利用一阶差分麦克风阵列技术对实测信号进行处理,利用由独立分量分析与二值掩膜组成的时频分解过程对混合信号进行初步划分,分解过程不断迭代直至满足终止条件;最后,合并同源信号得到各分离分量,通过将分量与缸盖表面和活塞敲击处振动信号进行对比,验证分离结果的正确性.结果表明:新算法能有效分离内燃机燃烧噪声与活塞敲击噪声,且性能稳定,计算量小.     

A framework for stochastic estimation of electric vehicle charging behavior for risk assessment of distribution networks

Power systems are being transformed to enhance the sustainability. This paper contributes to the knowledge regarding the operational process of future power networks by developing a realistic and stochastic charging model of electric vehicles (EVs). Large-scale integration of EVs into residential distribution networks (RDNs) is an evolving issue of paramount significance for utility operators. Unbalanced voltages prevent effective and reliable operation of RDNs. Diversified EV loads require a stochastic approach to predict EVs charging demand, consequently, a probabilistic model is developed to account several realistic aspects comprising charging time, battery capacity, driving mileage, state-of-charge, traveling frequency, charging power, and time-of-use mechanism under peak and off-peak charging strategies. An attempt is made to examine risks associated with RDNs by applying a stochastic model of EVs charging pattern. The output of EV stochastic model obtained from Monte-Carlo simulations is utilized to evaluate the power quality parameters of RDNs. The equipment capability of RDNs must be evaluated to determine the potential overloads. Performance specifications of RDNs including voltage unbalance factor, voltage behavior, domestic transformer limits and feeder losses are assessed in context to EV charging scenarios with various charging power levels at different penetration levels. Moreover, the impact assessment of EVs on RDNs is found to majorly rely on the type and location of a power network.     

Effect of corrosion inhibitors on hydrogen uptake by Al from NaOH solution

Corrosion rate, hydrogen permeation rate (hydrogen uptake) and stress corrosion cracking of Al were studied in NaOH solutions, pure and with the addition of H₃BO₃, EDTA, KMnO₄ and As₂O₃. The presence of the studied species in electrolyte and the implantation of Al surface with B⁺ ions inhibited corrosion. Hydrogen uptake was found to be promoted or inhibited by means of studied species, depending on the method of their introduction into the base solution and on the applied polarization. The observed different influence of corrosion inhibitors on the hydrogen uptake was associated with the different chemical composition and structure (revealed by XPS analysis) of the surface films, formed on Al under the various conditions. Under similar polarization conditions, the presence of H₃BO₃ in the base solution similarly affected the hydrogen uptake by Al and the susceptibility to stress corrosion cracking of the metal.     

Energy management strategy of Supercapacitor/Fuel Cell energy storage devices for vehicle applications

This paper addresses the management of a Fuel Cell (FC) – Supercapacitor (SC) hybrid power source for Electric Vehicle (EV) applications. The FC presents the main energy source and it is sustained with SCs energy storages in order to increase the FC source lifespan by mitigating harmful current transients. For this aim, the reported work proposes a Grey Wolf Optimizer (GWO) for an efficient power management of the studied hybrid power system. The key idea of the proposed approach is to incorporate the benefit of the GWO in terms of fast optimization and convergence accuracy, in order to achieve efficient energy sources exploitation and provide the desired driving performances. Simulations and experimental results verify the validity of the proposed management algorithm.     

Development of hybrid photovoltaic-fuel cell system for stand-alone application

In this paper we present firstly the different hybrid systems with fuel cell. Then, the study is given with a hybrid fuel cell–photovoltaic generator. The role of this system is the production of electricity without interruption in remote areas. It consists generally of a photovoltaic generator (PV), an alkaline water electrolyzer, a storage gas tank, a proton exchange membrane fuel cell (PEMFC), and power conditioning units (PCU) to manage the system operation of the hybrid system. Different topologies are competing for an optimal design of the hybrid photovoltaic–electrolyzer–fuel cell system. The studied system is proposed. PV subsystem work as a primary source, converting solar irradiation into electricity that is given to a DC bus. The second working subsystem is the electrolyzer which produces hydrogen and oxygen from water as a result of an electrochemical process. When there is an excess of solar generation available, the electrolyzer is turned on to begin producing hydrogen which is sent to a storage tank. The produced hydrogen is used by the third working subsystem (the fuel cell stack) which produces electrical energy to supply the DC bus. The modelisation of the global system is given and the obtained results are presented and discussed.     

A methodology for the performance evaluation of an experimental desiccant cooling system

An experimental investigation was conducted in an open cycle desiccant cooling system (DCS) operating on the ventilation mode in the laboratory site [M. Yıldırım, An experimental investigation on heat and mass transfer in a desiccant cooling system, PhD thesis, Gaziantep University, Turkey (2002). [1]]. Although the operation of DCS is presumably affected by the design of primary components of rotary regenerator (RR) and desiccant wheel (DW) the methodology used in the analysis of experimental data is presented in this paper to set a different approach for the performance evaluation of similar systems.

The rotational speeds of RR and DW (N_RR and N_DW), air mass flow rate (m_a) in process and regeneration lines, and the regeneration temperature (T_R) were defined as operation parameters. Meanwhile coefficient of performance (COP) and cooling capacity (CC) of the system were called as the performance parameters. The system operation with a variety of experimental conditions resulted in an extensive data set covering the ranges of N_RR, N_DW, m_a and T_R as 5 rpm ≤ N_RR ≤ 20 rpm, 0.1 rpm ≤ N_DW ≤ 0.4 rpm, 0.05 kg/s ≤ m_a ≤ 0.139 kg/s and 60 °C ≤ T_R ≤ 90 °C, respectively. The interactive influence of the operation parameters was determined through the realization of the psychrometric cycle in deviation from an ideal cycle. A dimensional analysis based on a trial and error procedure was followed to determine the functional relationship of COP and CC.

The proposed correlations between COP and CC and the introduced system performance parameter (PP) were determined to be a sole function of m_a independent of N_RR, N_DW and T_R in their covered ranges.     

Designing and modelling of the asymptotic perturbed extremum seeking control scheme for tracking the global extreme

This paper presents the designing and modeling of the Asymptotic Perturbed Extremum Seeking Control (aPESC) scheme that is capable to locate and track the Global Extremes on the multimodal patterns. The multimodal patterns may appear on power generated by a photovoltaic (PV) array under Partial Shading Conditions (PSCs), but also on net power generated by a Fuel Cell (FC) system. The proposed aPESC scheme uses a scanning technique to determine the GMPP on different multimodal patterns based on two components of the searching signal: (1) the scanning signal locates the LMPP by sweeping the PV pattern based on a asymptotic dither modulated by the first harmonic of the PV power and controlled by the dither gain (k₂); (2) the tracking signal finds and tracks accurately the GMPP based on similar loop used in PESC schemes proposed in the literature that is controlled by the loop gain (k₁). These tuning parameters are designed based on the averaged model of this aPESC scheme. Also, the averaged scheme and local averaged loop of the aPESCH1 scheme are used to estimate the searching gradient and analyze the closed ESC loop stability. The design methodology is tested on generic multimodal patterns and then is validated considering a PV system and a FC system.     

In-situ hydrogen peroxide synthesis with environmental applications in bioelectrochemical systems: A state-of-the-art review

Hydrogen peroxide (H₂O₂) is a versatile, eco-friendly, strong oxidizing chemical with numerous industrial applications. It is found that bioelectrochemical system (BES) is a promising technology for H₂O₂ biosynthesis including microbial fuel cell (MFC) and microbial electrolysis cell (MEC), generally. Since first discovery of H₂O₂ production in BES in 2009, a growing community of researchers payed attention to on-site H₂O₂ production and environmental applications based on BESs. In this review, we discussed the state-of-the-art development, performance and environmental applications of H₂O₂-BES in detail. The H₂O₂-BES has been getting more and more energy-saving even turning “waste” into wealth completely without other energy input. Moreover, coupling the H₂O₂-BESs with Fenton and ultraviolet/visible light is extensively employed for environmental applications, ranging from dye decolorization, metal deposition, emerging contaminants, real wastewater and primary sludge treatment in lab-scale. However, the pilot- or industrial-scale applications of BESs are challenging enough in environmental remediation up to now.     

Characterisation tools development for PEM electrolysers

Electrochemical impedance spectroscopy (EIS), current interrupt (CI) and current mapping (CM) were investigated as in-situ characterisation tools for PEM electrolysers. A 25 cm² cell with titanium anode and carbon cathode plates were utilised in this study. A commercial MEA consisting of 1 mg IrO₂/cm² on the anode and 0.3 mg Pt/cm² on the cathode was used. The electrocatalyst was deposited on Nafion^® membranes. The electrochemical losses in a PEM electrolyser namely: activation, ohmic and mass transfer losses were identified using EIS and CI and both the advantages and disadvantages of the methods were discussed. The current distribution over the membrane electrode assembly (MEA) at different current densities was measured using the current mapping method. It is also shown that under the given experimental conditions the current density decreases along the serpentine flow field.     

Miniaturized polymeric enzymatic biofuel cell with integrated microfluidic device and enhanced laser ablated bioelectrodes

The present work establishes a simple, customized, and economical laser-induced graphene (LIG) material produced using a CO₂ laser. The one-step LIG bioelectrodes have been further validated for Enzymatic Biofuel Cell (EBFC) application by integrating them into a microfluidic device, fabricated by the conventional soft-lithography on Polydimethylsiloxane (PDMS). This electrode and device manufacturing technology delivers a simple and quick fabrication method, which eliminates the necessity of any further amendment and post-processing. LIG electrodes were created at optimized CO₂ laser (5.1 W power and 0.625 cm s^?1 speed) irradiation which has been further modified by Multi-walled carbon nanotubes (CNT), called C-LIG electrodes, which offers improved performance and enzyme stability. In this novel study, CNT functionalized LIG electrodes have been incorporated into a microfluidic device for biofuel cell applications. LIG and C-LIG bioelectrodes have been integrated into a microfluidic device under the laminar fluid flow regime and the electrochemical and polarization study of the platform have been carried out. This C-LIG bioelectrodes integrated microfluidic device, without any metal catalyst, generated 2.2 μW/cm² power density with an optimized 200 μl/min flow rate which is 1.37 times higher than the LIG bioelectrodes. Such novel and simple EBFC platform is amenable to further improvement for generating even more power output by optimizing the LIG formation, alternate nano-functionalisation and mediator based electrochemical analysis.     

Optimal placement of PMUs for the smart grid implementation in Indian power grid—A case study

Efficient utilization of energy resources is essential for a developing country like India. The concept of smart grid (SG) can provide a highly reliable power system with optimized utilization of available resources. The present Indian power grid requires revolutionary changes to meet the growing demands and to make the grid smarter and reliable. One of the important requirements for SG is the instantaneous monitoring of the voltage, current and power flows at all buses in the grid. The traditional monitoring system cannot satisfy this requirement since they are based on nonlinear power flow equations. Synchro-phasor-measurement devices like phasor measurement units (PMUs) can measure the phasor values of voltages at installed buses. Consequently, the currents passing through all branches connected to that bus can be computed. Since the voltage phasor values at the neighboring buses of a bus containing the PMU can be estimated using Ohm’s law, it is redundant to install PMUs at all the buses in a power grid for its complete observability. This paper proposes the optimal geographical locations for the PMUs in southern region Indian power grid for the implementation of SG, using Integer Linear Programming. The proposed optimal geographical locations for PMU placement can be a stepping stone for the implementation of SG in India.