一种三态加时变迁Petri网的形式化描述与分析

提出一种弱引发规则三态加时变迁Ｐｅｔｒｉ网（简称ＷＴＴＰＮ），它比现有三态加时变迁Ｐｅｔｒｉ网更适于建模分析冲突结构；平行于无时间约束Ｐｅｔｒｉ网，给出了并发意义下ＷＴＴＰＮ的形式化描述与分析框架，据此可对其进行定性分析；证明了ＷＴＴＰＮ与其基网系统关于活性、有界（安全）性和可逆性等价。     

基于单片机的RTU三相交流采样技术

描述一种基于80C51系列单片机实现三相交流采样的典型RTU(远程终端)的基本结构,介绍其采样信号预处理模块的原理,以MAXIUM公司模数转换芯片MAX125为核心构建一个应用电路。通过分析三相交流算法的特点,给出适合单片机实现的时域积分算法和离散傅氏变换算法的表达式,还给出基于C语言算法实现的3个重要模块。     

交流三相温升试验能用交流单相串联试验替代吗?(续)

在交流三极电器的温升试验中,能否用三极串联通以单相交流试验电流来替代三极中通以交流三相试验电流?这取决于在2种试验方法下,电器各极间的电磁邻近效应是否能够忽略.本文通过理论分析和试验验证得出:具有并联支路的三极电器,其温升试验不可用交流单相串联来替代交流三相.     

固定化细胞在三相流化床中发酵生产木糖醇

为了建立一种成本低、产率高、能连续高效地生产木糖醇的新工艺,研究了固定化假丝酵母(Candida sp.)细胞在三相流化床内分批发酵玉米芯半纤维素水解液生产木糖醇这一工艺过程.适宜的工艺条件为:32℃,起始木糖质量浓度100g/L,固定化细胞与发酵培养基体积比1:3.8,分段通气:0～24 h,0.5 L/min;24～80 h,0.175 L/min.利用固定化细胞重复进行6批发酵,木糖醇得率平均为63.5%.玉米芯半纤维素水解液未经脱色以及离子交换等脱毒处理便可直接有效地转化成木糖醇;三相流化床生物反应器动力消耗少、流化状态稳定均匀.该方法大大降低了原料预处理的成本,发酵结果较好.     

Non-Newtonian Fluids in Spout-Fluid Beds: Mass Transfer Coefficient at Low Reynolds Numbers

Following on from the work of Anabtawi et al. (2003), this study examined how the volumetric liquid-phase mass transfer coefficient, k_La, of oxygen in air in three-phase spout-fluid beds was affected by varying the system parameters of bed height, bed diameter, gas velocity, and liquid velocity. The liquid used was 0.1% CMC solution, displaying a pseudo-plastic rheology, with 1.75 mm glass spheres as packing. The values of the Sherwood number were lower than in previous studies (Anabtawi et al., 2003), in the range 9,000-186,000. Gas velocity had a similar effect on k_La as in a bubble column, with results also giving good agreement with previous work on two-phase and three-phase spouted bed systems. The correlation obtained for the effect of liquid velocity on k_La compared well with that of Schumpe et al. (1989). An increase in the height of packing increased k_La to the power of 0.319, with an increase in column diameter also causing an increase in k_La, which is in agreement with the results of Akita and Yoshida (1973).     

多端直流架构的交直流混合配电网三相不平衡潮流计算

在配电网向交直流混合供电的方向发展的新形势下,提出一种能够计及交流三相不平衡的交直流配电网潮流计算方法。首先建立了电压源型换流器的三相稳态潮流模型,推导了换流器的三相潮流以及直流配电网潮流计算方程,并对不平衡系统进行了补偿。考虑了不同的控制方式及适用于配电网的多端直流控制策略,在此基础上,提出了适合配电网的三相不平衡交直流交替迭代潮流计算方法,该方法采用了模块化思想,不需要全局迭代,可以从交、直流侧任意方向开始潮流计算,自动修正越限变量并调用控制策略,实现了交直流潮流计算的解耦。最后,对修改的IEEE 37节点配电系统进行仿真计算,仿真结果证明了算法的有效性、快速性和准确性。     

On the problem of optimal estimation of balanced and symmetric three-phase signals

This paper revisits the fundamental problem of optimal estimation of the magnitude and phase of balanced and symmetric three-phase voltage or current signals. We analyze and compare various setups for the corresponding optimal Kalman filter, including the direct use of three-phase measurements, as well as measurements subjected to the Clarke transform in real or complex form. One contribution is to show that the standard practice of disregarding the transformed zero-component of the Clarke transformed three-phase signal almost always leads to a sub-optimal performance of the Kalman estimator. Our analysis extends to show that the closely related complex Kalman estimator is also sub-optimal and that optimal performance can be recovered if the zero-component is made available to the filter provided that the noises are properly characterized. These results are illustrated by means of simple numerical examples, which also highlight the importance of correctly modeling the noise characteristics if a real or complex form of the Clarke transformation is to be used. We conclude the paper with a unified set of guidelines or best practices regarding the use of optimal Kalman estimators for balanced and symmetric three-phase signals.     

18脉冲自耦变压整流器分析及不对称输入仿真

分析了不对称18脉冲ATRU的工作原理和输入输出电流的基本特性。针对三相电源输入不对称对变压整流器的影响进行仿真,并完成样机的基本特性实验、三相不对称实验和实验数据分析。     

Phenomena at three-phase electroslag remelting

The electroslag remelting (ESR) process is widely used to produce high-quality ingots and billets for high-alloyed steels and alloys.Both the single-phase and three-phase alternating current diagram with bifilar and monofilar connection are in use for heavy ingot manufacturing.The numerical simulation of the three-phase bifilar circuit for the 120 t three-phase bifilar six-electrode ESR furnace at different variants of electric connection was presented and discussed.At the bifilar diagram of power supply,the geometrical location of electrodes in a mould holds critical importance for performances:the close location of bifilar pair electrodes provides the highest heat productivity,but the equidistant location of electrodes gives a much more uniform heat distribution.The monofilar mulit-electrode diagram of three-phase connection without phase shift shows the most uniform distribution of potential and heat generation as well as a favorable magnetic field that makes this kind the most promising for providing a high quality of heavy ingots.     

基于ATmega128A的三相正弦波发生器的研究与设计

近年来,逆变技术作为一种高效的节能技术已经渗透到各个领域。目前,逆变电源的控制多采用正弦脉宽调制技术（SPWM）,SPWM波大多用高性能的DSP生成。虽然这种技术已经很成熟,但多数DSP的外围电路开发时存在一些难度。此外,DSP的成本仍比单片机要高出不少。本文设计了一种基于ATmega128A的可用于回馈控制系统的三相正弦波发生器,利用软件编程产生 SPWM 波,滤波后得到三相正弦波。其控制电路简单,能够降低外界干扰。通过实验证明,该发生器可以通过软件最终生成三相正弦波,并实现过零点匹配和相位匹配控制,具有良好的实时性和快速性。