基于融合熵时段划分的三相配电网动态重构

针对大规模电动汽车接入配电网带来的三相不平衡程度加剧问题,提出一种基于融合熵时段划分的三相配电网动态重构方法。在Fisher-最优分割的基础上,融合曲线的信息熵,对蒙特卡洛模拟得到的等效日负荷曲线进行更加精准合理的时段划分;将动态重构策略引入三相配电网中,以三相不平衡度最低为目标建立配电网重构模型;改进传统的帝国主义竞争算法,在殖民地革命环节中引入复合型微分进化思想,并提出自适应帝国合并机制以提高算法的收敛速度和精度。IEEE 33节点系统仿真结果表明,所提方法能对曲线进行合理的分段重构,并且有效解决了配电网中的三相不平衡问题。     

两种12脉波整流变压器分析与仿真

比较两种12脉波整流变压器的结构和设计原理。一种利用阀侧的星三角自动30度移相,电源侧采用延边三角形移相。第二种电源侧采用自耦调压绕组,整流分裂为高低压两套绕组,延边三角形在整流变高压侧,都为三角形联结,在整流绕组的高压侧实现相位的左右移相。前者结构简单,造价较低,电压可调性较差。后者变压器绕组增多,结构复杂,高度、造价增加,但调压灵活,多用于需要频繁调压的领域。     

套管扶正器位移检测系统下位机设计

本文详细介绍了套管扶正器位移检测系统下位机部分的设计过程,包括增量式编码器的选用及其原理介绍、位移量显示与PC机通信等电路的设计和软件的编制。本系统采用精度很高的增量式编码器,选用通用外围电路,硬件结构简单,软件编程容易实现,测量精度高,可在其它短距离、高精度的位移测量中推广。     

面向产品族优化时间窗下可重入批处理机调度

在半导体晶圆制造系统中,具有不确定交货时间窗和不相容产品族的可重入批处理机优化调度是NP-难问题。针对该问题,提出面向产品族的三层滚动混合整数线性规划模型的优化调度算法,其优化目标是提前和误工的时间总和最小。该算法是基于时间序列模型和事件模型的混合分解策略,在可重入批处理机空闲、可用的事件触发下,将整个调度时间轴分解为滚动的时间域;每个时间域对应一个子问题;每个子问题分解为三层:排序、派工和更新;半导体晶圆制造系统实时调度仿真平台用于派工、更新和时域滚动,混合整数线性规划模型用于排序。通过6种典型情形实例验证,结果表明面向产品族的三层滚动混合整数线性规划模型能够在较短计算时间内获得较好优化解。     

SVM控制的复合有源箝位(CAC)ZVS三相功率因数校正器(PFC)

提出了一种采用CAC的三相软开关功率因数校正变换器，应用改进的空间矢量控制方案，可以有效的抑制桥臂开关反并联二极管的反向恢复，减少反向恢复损耗。并且所有的主开关和辅助开关均为零电压开关，而且具有开关器件电压应力较低的特点。还具有开关频率固定、输入波形品质好的特点。研制了一台基于DSP控制的4kW的实验样机。     

交流电机的定子绕组展开图分析

各类交流电机定子绕组的结构型式很多,但基本要求一致,转子绕组与定子绕组亦有许多相似之处。文章通过对绘制交流电机定子绕组展开图过程的分析,提出统一绘制三相对称绕组展开图的程序。     

基于ADHDP方法的HVDC整流控制器设计

针对传统PI控制器在HVDC系统受到大干扰时难于产生有效控制作用的问题,设计了一种基于执行依赖启发式动态规划(ADHDP)方法的整流控制器,控制器的执行网络和评价网络均采用BP神经网络进行设计,并利用直流线路电流偏差信号在线训练两个网络以优化控制器性能.仿真结果表明,与传统PI控制器相比,所设计的的控制器具有更好的控制效果.     

12脉波整流电路类比式探索教学模式研究

针对12脉波整流电路理解晦涩、不易讲解的教学难题,提出了类比式探索这一新型教学模式。此模式采用“仿真-类比式探索-再仿真验证”的实践方法,借助Matlab/Simulink仿真工具,实现学生对知识点的自主学习。通过具体实践过程的展示,对该教学模式进行效果评估和反馈,以期认识类比式探索教学模式的优势和短板,为今后其他课程的教学提供参考。     

Effect of length of gas/liquid/solid three-phase boundary zone on cathodic and corrosion behavior of metals

Liquid dispersion, depending on the length of gas/liquid/solid three-phase boundary (TPB) zone of dispersed liquid on a metal surface, is an important property of liquid state influencing corrosion behavior of metals in gas/liquid/solid multiphase corrosion systems. The effect of TPB length on the cathode and corrosion process was studied using steady state polarization technique, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) technique. It was found that both the cathodic limiting current density and corrosion current density linearly increased with increasing the TPB length, indicating that the cathodic and corrosion process in gas/liquid/solid multiphase corrosion systems not only depended on the thickness of liquid layer but also strongly depended on the dispersed liquid state on a metal surface. In addition, a model is developed to establish the relationship between the cathodic limiting current density and the TPB length. The simulation result is in good agreement with the experimental findings. The model is also useful for evaluating the effect of liquid dispersion on atmospheric corrosion rates.     

Operation and control of batch extractive distillation for the separation of mixtures with minimum-boiling azeotrope

Batch distillation is commonly used in the fine chemicals, specialty polymer, biochemical, pharmaceutical, and food industries. For separating mixtures with minimum-boiling azeotrope, a heavy entrainer is frequently added to the top section of the batch column to aid in the separation. This process is called batch extractive distillation. Most of the papers in open literature have only studied the first operating step of the batch extractive distillation which is the recovery of the light component without mentioning the later steps for the recovery of the other component and entrainer. In this paper, two real chemical systems, one separating acetone and methanol using water as entrainer and the other separating isopropyl alcohol (IPA) and water using dimethyl sulfoxide (DMSO) as entrainer, are studied for the feasible operation of the complete batch distillation sequence. The operating variables, including the pre-load amount with the mixture, continuous feed rate of the entrainer, and reflux ratio at each operating step are determined in the operating sequence. The constant reflux ratio and constant entrainer feed rate operating policy and another policy to allow these two operating variables to be varied will be compared in order to further improve the batch operation. All dynamic simulations that are performed directly mimic industrial situations from an empty column using a rigorous dynamic simulator, Aspen Dynamics™.