Sampled-data modeling and dynamical effect of output-capacitor time-constant for valley voltage-mode controlled buck-boost converter

By analyzing the output voltage ripple of a buck-boost converter with large equivalent series resistance（ESR） of output capacitor, one valley voltage-mode controller for buck-boost converter is proposed. Considering the fact that the increasing and decreasing slopes of the inductor current are assumed to be constant during each switching cycle, an especial sampleddata model of valley voltage-mode controlled buck-boost converter is established. Based on this model, the dynamical effect of an output-capacitor time-constant on the valley voltage-mode controlled buck-boost converter is revealed and analyzed via the bifurcation diagrams, the movements of eigenvalues, the Lyapunov exponent spectra, the boundary equations,and the operating-state regions. It is found that with gradual reduction of output-capacitor time-constant, the buck-boost converter in continuous conduction mode（CCM） shows the evolutive dynamic behavior from period-1 to period-2, period-4, period-8, chaos, and invalid state. The stability boundary and the invalidated boundary are derived theoretically by stability analysis, where the stable state of valley voltage-mode controlled buck-boost converter can enter into an unstable state, and the converter can shift from the operation region to a forbidden region. These results verified by time-domain waveforms and phase portraits of both simulation and experiment indicate that the sampled-data model is correct and the time constant of the output capacitor is a critical factor for valley voltage-mode controlled buck-boost converter, which has a significant effect on the dynamics as well as control stability.

An Approach towards Pulse Data Transmission Using Modified Negative Luo Converter (MNLC) for Telecoms

Telecom sectors generally operate at negative voltages to reduce the effect of corrosion caused in the metallic wire due to electrochemical reaction while communicating signals. To feed those lines and to have an effective digital data transmission, a power electronic converter referred as Modified Negative Luo Converter (MNLC) is proposed in this paper. MNLC is a high gain converter in which the output voltage increases in geometric progression. This paper portrays a novel concept of a 50 Hz pulse data transmission through RLCG (Resistance-inductance-capacitance with a shunt conductance) transmission line using MNLC. Signal frequency of 50 Hz to be transmitted is anded with a high frequency pulse that charges and discharges MNLC and produces the boosted negative output voltage. The boosted output is again transmitted through the RLCG transmission line from which 50 Hz data pulse is retrieved at the output of the transmission line by comparing with a comparator signal. This sort of MNLC aided data transmission not only introduces less loss in its transmitted data but also overcomes various health hazards of conventional radio frequency (RF) communication. This technique also proves that any data bit stream can be transmitted and retrieved using the proposed high gain DC-DC converter. The simulation model of the proposed system is implemented in MATLAB for various switching frequencies with its prototype of the converter developed and the results are verified.

Design and implementation of 1 GHz high speed data acquisition system

With the development of current electronic technology, numerous high-speed data acquisition systems provide a variety of potential benefits. This article describes a high-speed data acquisition system which consists of ECL logic and TTL logic devices, samples and stores data with a 1 GHz clock. This system is accomplished easily and works stably. A performance test of this system has been undertaken and the results show that the effective number of bits （ENOB） is more than 6.5 bits.

Pushing Multiple Convertible Constrains into Frequent Itemsets Mining

Constraint pushing techniques have been developed for mining frequent patterns and association rules. How ever, multiple constraints cannot be handled with existing techniques in frequent pattern mining. In this paper, a new algorithm MCFMC （mining complete set of frequent itemsets with multiple constraints） is introduced. The algorithm takes advantage of the fact that a convertible constraint can be pushed into mining algorithm to reduce mining research spaces. By using a sample database, the algorithm develops techniques which select an optimal method based on a sample database to convert multiple constraints into multiple convert ible constraints, disjoined by conjunction and/or, and then partition these constraints into two parts. One part is pushed deep inside the mining process to reduce the research spaces for frequent itemsets, the other part that cannot be pushed in algorithm is used to filter the complete set of frequent itemsets and get the final result. Results from our detailed experi ment show the feasibility and effectiveness of the algorithm.

The Adjust Data with the Laboratory PVT Reports that Are Applied in the Oil Wells Designs

The correlations have been developed with the flash data to predict the multiphase flow and mass transfer in the oil wells designs. Therefore, the laboratory pressure/volume/temperature (PVT) reports require calculation of the flash Oil Formation Volume Factor and the flash Solution Gas/Oil Ratio data starting from Differential Liberation tested data. Once these parameters are known, the oil density and other thermophysical properties can be determined by a complete model for the different states of pressure and temperature in the well during its production life and initial design. The subject of this paper is how to read and make proper use of information contained in the IMP laboratory PVT reports, for the oil wells designs. The discussion is focused on the laboratory report for the well number 407 located in the Maloob field in Mexico.

面向数据中心48 V供电系统的混合型母线变换器及其高密度集成

该文提出适用于数据中心48 V供电系统的混合型母线变换器电路拓扑及其高密度集成方法,通过在开关电容变换器中嵌入自耦变压器和LLC谐振变换器,大幅增加开关电容变换器的降压比,且利用矩阵式变压器结构实现变换器输出电流能力的大幅提升。基于所提出的混合型母线变换器,进一步提出其高密度集成方法,综合采用磁集成、绕组集成等方式,实现变换器功率密度和效率的提升。研制40~60 V输入、变比8:1、输出电流100 A、开关频率1 MHz的八分之一砖模块,功率密度达到1.704 kW/in3,最高效率达到97.9%。

Data Acquisition System for Electron Energy Loss Coincident Spectrometers

A Data Acquisition System （DAQ） for electron energy loss coincident spectrometers （EELCS） has been developed. The system is composed of a Multiplex Time-Digital Converter （TDC） that measures the flying time of positive and negative ions and a one-dimension positionsensitive detector that records the energy loss of scattering electrons. The experimental data are buffered in a first-in-first-out（FIFO） memory module, then transferred from the FIFO memory to PC by the USB interface. The DAQ system can record the flying time of several ions in one collision, and allows of different data collection modes. The system has been demonstrated at the Electron Energy Loss Coincident Spectrometers at the Laboratory of Atomic and Molecular Physics, USTC. A detail description of the whole system is given and experimental results shown.

大功率履带越野车用液力变矩器循环工况构建

为解决液力变矩器的传统稳态试验工况同实车工况契合度不高、无法反应实车上运行状态的问题,提出了一种大功率履带越野车用液力变矩器循环工况。在某型履带车辆实车工况数据基础上,统计分析液力变矩器在实车运行中的工况特征,选取了12个统计特征参数和10个比例特征参数,利用主成分分析法对工况数据进行了降维处理,通过无监督学习中的K均值聚类算法完成了数据片段的聚类分析,使用动态规划方法整合闭锁工况,获取典型工况片段用于循环工况重构,利用汉宁窗对片段进行平滑连接。以循环工况与总体数据主要特征值平均误差、连接处转速差值总和及斜率差值总和为目标,借助模拟退火和多目标粒子群算法进行优化,构建基于实车数据、契合液力变矩器实车运行特征的循环工况。结果表明,最终所得工况由叶轮转速——时间和闭锁信号——时间组成,主要特征参数平均相对误差为2.92%,与实车数据的工况特征表现一致。本研究成果为设计液力变矩器的可靠性试验工况提供了一种新的思路和途径。

基于机理和反向传播神经网络的转炉石灰加入量计算模型

针对高废钢比转炉冶炼条件,以转炉碱度计算为理论基础,以某钢厂转炉一级和二级的数采系统为数据来源,利用设计数据筛选规则、数据预处理和计算损失函数提高计算精度,构建了基于机理+结构为15-3-50-5-1的反向传播(BP)神经网络的石灰加入量计算模型,并将计算结果与真实值和传统模型计算结果进行了对比。结果表明:机理+BP神经网络模型预测的石灰加入质量与真实值的平均相对误差仅为10.7%,相较传统计算模型下降约7%,说明构建的新模型预测误差小、精度高。

红外测温技术在换流阀温度监测中的应用

随着工业自动化的发展,高效且准确的设备监控技术逐渐受到重视。在电力系统中,换流阀作为关键组件,其温度监测对于系统的稳定运行至关重要。基于此,文章探讨红外测温技术在换流阀温度监测中的应用及其优势。一方面,分析红外测温技术的原理和不同应用场景的需求;另一方面,展示红外测温技术在实际工业环境中的适用性和高效性。研究结果表明,应用红外测温技术能够更准确、实时地监测温度数据,对于预防设备故障和优化维护计划具有重要价值。

Towards Practical Implementation of Data and Energy Integrated Networks

With the rapid development of the mobile internet and the massive deployment of the Internet of Things, mobile devices, including both the consumer electronics and the sensors, become hungrier for the energy than ever before. Conventional cable based charging largely restrict the movement of the mobile devices. Wireless charging hence emerges as an essential technique for enabling our ultimate goal of charging anytime and anywhere. By efficiently exploiting the legacy of the existing communication infrastructure, we propose a nov- el data and energy integrated network （DEIN） in order to re- alise the radio frequency （RF） based wireless charging with- out degrading the information transmission. In this treatise, we focus on the implementation of the DEIN in both the theoretical and practical aspects, concerning the transceiver architecture design and the rectifier circuit design. Furthermore, we also present a Wi-Fi based testbed for demonstrating the availability of the RF based wireless charging.

基于联合功率量/载波调制的DC-DC变换器功率/数据复合传输方法

DC-DC变换器可以同时进行功率变换和数据传输。针对较低通信速率限制功率/数据复合传输(power/data multiplexing transmission,PDMT)应用的难题,提出一种联合功率量/载波调制(joint power/carrier modulation,JPCM)的新方案。与传统二进制PDMT方案不同,JPCM同时对功率量/载波进行2FSK调制,实现两种数据并行传输,可以看作一种四进制FSK,有效提高通信速率。相较于传统四进制PDMT方案,JPCM方案解调环节所需带通滤波器数目可减少一半,且软件开销更低。首先,证明PDMT在理论上的可行性;然后,根据4种不同电压纹波频率配置不同码元,并设计了包含高低数据位调制的JPCM和基于滑动傅里叶变换的数据解调方案;此外,重点分析输出参考电压突变对通信的影响,动态调整阈值可有效抑制误码;最后,搭建一个由2个Buck变换器并联的实验装置,实验结果表明在稳态、负载突变和输出参考电压突变的工况下,JPCM方案均能实现20 kb/s的通信速率,验证了该方案的有效性。

基于QFSK调制的DC-DC变换器功率/数据复合传输方法

传统电力线通信方案的硬件设计较为复杂。DC-DC变换器具有发送数据的潜能,可进行功率/数据复合传输。文中提出一种基于四进制频移键控(QFSK)调制的电力电子开关调制方案,通过调制开关频率将数据信息嵌入原始脉宽调制(PWM)信号中,使得电压纹波携带数据的频率特征;再通过基于滑动离散傅里叶变换的解调方案实现数据接收,最终实现功率/数据的同步传输。首先,证明了PWM信号与电压纹波频率一致的关系;然后,给出数据调制与解调的方案;以负载突变工况为例,通过对Buck变换器建模,分析功率变换暂态过程对通信的干扰影响;最后,搭建由两个Buck变换器组成的实验平台,验证了所提方案可实现20 kbit/s的通信速率;并以光伏优化器为应用背景,验证了所提方案的有效性。

实际次/超同步振荡事件的多频率耦合效应分析

随着新能源和电力电子设备的占比增加,电力系统的宽频振荡问题日益严峻,且往往伴随着多个频率的振荡分量耦合出现的现象。为了明确新能源电力系统振荡过程中多频率耦合效应的机理和特性,基于典型电力电子变流器并网系统,推导并梳理了变流器在电压扰动作用下输出多阶耦合频率分量的过程,阐明了锁相环控制及坐标变换、dq轴控制不一致等造成变流器并网系统多频率耦合效应的主要原因。最后,结合实际电网的2次振荡录波数据分析,验证了多频率耦合机理分析的准确性。

数据驱动的高比例变流器电力系统低频动态模型参数辨识

高比例变流器接入弱网后,容易产生由“外环控制-锁相环-弱网”交互影响主导的低频动态现象。网络侧线路参数、变流器控制参数因技术保密等原因往往难以完全获取,导致低频动态稳定性分析模型难以构建。因此,提出了一种基于数据驱动的低频动态稳定性分析模型参数辨识方法。首先,通过最小二乘回归算法辨识出网络参数矩阵;其次,建立系统矩阵,采用基于奇异值分解的动态模式分解算法将其重构,代入对应控制环节,通过求解一组线性方程即可同时获得所有变流器外环及锁相环的控制参数;然后,结合设备侧模型,构建完整的系统小信号稳定性分析模型;最后,在PSCAD/EMTDC中搭建2个新能源场站接入系统的算例,以验证参数辨识的准确性以及模型的有效性,并进一步分析系统的低频动态稳定性。

柔性直流换流站异常监控数据实时预警研究

为了提高对异常数据的预警性能、维护柔性直流换流站的运行稳定性,提出了柔性直流换流站异常监控数据实时预警方法。首先,利用经验规则消除数据碰撞问题,根据数据信息哈希函数的异常值,准确检测出其中的异常数据。然后,利用小波变换对异常监控数据进行预处理,并从异常数据中提取关键变量信息。最后,根据监控过程中出现异常数据的概率,设定预警阈值,再利用预警函数构建实时预警模型。试验结果表明,应用该方法后,误报率被控制在20%以下,平均绝对误差被控制在0.12以下。相比于传统方法,该方法的预警结果更有效、准确率更高。

面向无损检测系统的数据转换器的设计与实现

针对PLC比较适合小规模的生产和较简单的控制任务,不适合检测大型曲面复合材料的问题,提出了采用机械臂作为运动部件,大型机械臂具有超大工作空间、高定位精度、灵活性好和空间可达性好等优点,不仅能检测小型平面复合材料,也能检测大型曲面的复合材料。由于市场上的机械臂大部分是通过TCP协议进行数据传输,不能直接转换成脉冲信号,提出了一种基于STM32芯片的数据转换器,能实时地接收机械臂位置数据并转换成的脉冲信号发送给超声检测仪,将机械部分和超声部分联系起来形成一个整体,使机械臂也可以作为无损检测的运动部件使用。无损检测实验室的实际应用效果表明,该装置在无损检测系统中的应用,扩展了复合材料检测的范围,对推动国内无损检测行业发展有借鉴价值。

多传感器融合下后勤物资采供数据远程采集技术

后勤物资采供涉及多个环节和数据源,这些数据源的数据格式、结构和标准各不相同,导致数据源的分散和多样性,增加数据采集的难度。为此,研究多传感器融合下后勤物资采供数据远程采集技术。分析多传感器融合下后勤物资采供数据远程采集技术总体架构,利用多传感器采集后勤物资采供原始数据,并将其汇总至A/D转换器,经A/D转换器实现数据形式转换,将转换后的后勤物资采供原始数据传输至数据预处理与融合单元。采用改进自适应加权融合算法预处理多传感器采集的原始数据并融合,实现后勤物资采供数据的远程采集。实验结果表明,所提方法的接收数据量时间较短,可有效实现后勤物资采供数据融合,且融合后数据较为完整,具有较好的后勤物资采供数据远程采集效果。

数据中心水泵与变频器的安全提升实践

目前,数据中心发展迅猛,在注重节能降耗的同时,机组设备的安全运行也是一个不容忽视的问题。本文以数据中心冷冻水空调系统的水泵和变频器为研究对象,以安全运行提升为出发点,结合实际运维经验,首先提出变频器在谐波、保护整定、低电压保护和接地故障的预防措施;然后针对恒压供水补水泵,从扬程核算、目标压力优化和泵组轮换规则展开阐述;最后,对于冷冻水泵、冷却水泵,提出多组低频节能运行、高水温运行的水泵功率分析和流量检查。

多判据融合的换流站监控数据异常甄别系统

换流站监控数据中存在部分异常数据,如果无法有效融合全部异常数据,会造成异常数据维度过大,导致甄别结果不精准,为此设计了基于多判据融合的换流站监控数据异常甄别系统。以MSP430单片机为核心,通过双存储器传输传感信号。设计可视甄别模块,计算两个图像圆点中心坐标距离,以此为依据,判断甄别点与设定阈值之间的关系。检测和筛选换流站监控异常数据,融合多判据数据特征,对数据进行降维处理,降低异常数据维度。构建LSTM分位数回归多判据融合模型,识别电流、电压、功率时间序列,获取置信区间范围,结合曲线斜率甄别异常数据,避免人为设置阈值给甄别结果带来的不确定性。由实验结果可知,该系统甄别出的电压、电流异常节点与实际异常节点数量一致,分别是3个和2个,说明使用该系统能够精准甄别异常数据。