A circulating current control scheme for multiple three‐level NPC inverter systems

In recent years, motor drive systems for steel rolling mills have been steadily increasing in capacity. In particular, the development of three‐level NPC (Neutral Point Clamped) inverters is now focusing on the replacement of cycloconverters. In order to satisfy such a requirement, in this paper a multiple three‐level NPC inverter system is proposed. The configuration consists of two three‐level NPC inverters with the same configuration connected in parallel by current limiting reactors. In this case, the circulating current flowing between the two three‐level NPC inverters must be controlled to prevent a decrease in the maximum output capacity. In particular, a new method for control of the circulating current is a major topic of discussion. The method is based on space voltage vector‐based PWM (Pulse Width Modulation) control for the three‐level NPC inverters and the circulating current is controlled by adjusting the output durations of the respective space voltage vectors. In this method the circulating current controller can be decoupled from the motor current controller. Therefore, it is possible to design the different controllers independently. In addition, the experimental results obtained using an induction motor show that the circulating current can be reduced to within 2% of the rated motor current when the motor current response exceeds 1000 rad/s. © 2001 Scripta Technica, Electr Eng Jpn, 136(2): 38–48, 2001     

电力电子教学中单相桥式逆变电路的讲解方法

单相桥式电路是一种基础且应用广泛的DC/AC逆变电路。在“电力电子技术”课程中,学生需要深刻理解和掌握单相桥式电路。但在教学实践中,往往直接给出全/半桥电路结构,只注重各模态波形绘制和公式推导,忽略桥式电路拓扑的由来,导致学生难以深入理解桥式逆变电路的本质原理。本文借助于简单易懂的Buck电路,提出一种渐变推演全/半桥逆变电路拓扑的教学方法。该教学方法不仅能够让学生循序渐进地理解桥式逆变电路的产生及其在单/双极性调制下的工作原理,同时能够增强学生对电力电子拓扑推演的理解和思考,提高对电力电子课程的学习兴趣。最后通过Matlab/Simulink软件的可视化功能进行仿真演示,增强课程的互动性,以期取得良好的教学效果。     

电子变频技术在混凝土振动器上的应用

基于电子变频器在变频电源上的应用实际,介绍混凝土振动器中机械式变频机组和电子变频器结构参数以及抑制谐波的基本方法,展望其应用前景。     

10MW级高压变频器在合成氨装置主机系统中的应用分析

本文通过对现有40万t合成氨装置主压缩杌组驱动系统分析，指出了其中存在的问题。针对性提出采用电气驱动替代“锅炉＋汽轮机”驱动的新思路：通过对两种驱动形式的经济性比较，技术可行性分析，阐述了该新型驱动形式的可行性和良好应用前景。     

Compact modeling of 0.35 μm SOI CMOS technology node for 4 K DC operation using Verilog-A

Compact modeling of MOSFETs from a 0.35 μm SOI technology node operating at 4 K is presented. The Verilog-A language is used to modify device equations for BSIM models and more accurately reproduce measured DC behavior, which is not possible with the standard BSIM model set. The model presented exhibits convergent behavior and is shown to be experimentally accurate at 4 K. No design tool currently in place exhibits convergence and/or accuracy over this range. The Verilog-A approach also allows the embedding of nonlinear length, width and bias effects into BSIM calculated curves beyond those that can be achieved by the use of different BSIM parameter sets. Nonlinear dependences are necessary to capture effects particular to 4 K behavior, such as current kinks. The 4 K DC behavior is reproduced well by the compact model and the model seamlessly evolves during simulation of circuits and systems as the simulator encounters SOI MOSFETs with different lengths and widths. The incorporation of various length/width and bias dependent effects into one Verilog-A/BSIM4 library, therefore, produces one model for all sets of devices called up in a given product design kit (PDK) for this technology node.     

油气地球化学勘探技术发展现状与方向

地表油气地球化学勘探作为一种直接找油方法，经过了曲折的半个多世纪的发展，已经逐步得到油气勘探工作者的承认，并在整个油气勘探程序中占据了它应有的地位；二连盆地吉尔噶郎图凹陷的稀油勘探和塔里木盆地大宛齐地区浅层油气藏的滚动勘探应用实例表明，该方法在浅层油气田勘探领域具有较好的勘探效果。认为K-V指纹法是一项在油气田目标详查阶段可发挥很好作用的实用技术，而井中化探方法是油气化探一个新的、具有实效的应用方法，在储层预测和评价方面可发挥其他方法不可替代的作用，具有良好的发展前景。     

异步电力测功电机转矩和损耗的研究

研究了异步电力测功电机的转矩和损耗，提出了变频调速系统对测功电机的设计要求，并根据电磁计算方法和程序实际设计了一台测功电机，实验结果表明，该设计方法和程序是正确和有效的。     

Adaptive output feedback stabilization for a class of nonlinear systems with inherent nonlinearities and uncertainties

This paper investigates the problem of adaptive stabilization by output feedback for a class of uncertain nonlinear systems. The distinguishing feature of such a class of systems is the presence of uncertain control coefficient and unmeasured states dependent growth with growth rate of polynomial‐of‐output multiplying an unknown constant. First, new high‐gain K‐filters with two dynamic gains are introduced, and an appropriate state observer is constructed based on the K‐filters. Then, motivated by the universal control idea, the backstepping scheme is successfully developed for the adaptive output feedback control design. By appropriate choice of the design parameters, the global stability of the closed‐loop system can be guaranteed. Finally, numerical simulations are provided to illustrate the correctness of the theoretical results. Copyright © 2010 John Wiley & Sons, Ltd.     

Fluctuations in light intensity modulate ion fluxes from grape berry mesocarp: direct evidence from microelectrode ion flux estimations

Canopy architecture and light spectral composition have long been considered as important factors determining grape juice acidity and K+concentrations. In this study, we provide direct evidence that fluctuations in intensity of light incident on berry tissue may significantly modulate net ion fluxes from and into the berry mesocarp. The MIFE technique was used to quantify fluxes of K+, H+, and Ca²⁺in Pinot Noir and Emperor grape berries. Transition from dark to light induced complex multiphase kinetics of K+flux resulting in significant shift towards net K+uptake by the peripheral mesocarp tissue. When light intensity was modulated in a square-wave manner with a period of 5 to 15 min (mimicking periodicity of natural variations during a typical autumn day in Hobart), K+flux oscillated with the same frequency and a magnitude of about 100 nmol/m²s. Changes in H+and Ca²⁺fluxes showed high positive (R = 0.8) and negative (R = 0.9) correlation, respectively, with those in K+. To the best of our knowledge, these data from excised fruit provide the first reported evidence that light directly incident on bunches may modulate apoplasmic pH and K+concentration in grape. Possible underlying mechanisms are discussed.     

The Chemical Biology of Phosphoinositide 3‐Kinases

Since its discovery in the late 1980s, phosphoinositide 3‐kinase (PI3K), and its isoforms have arguably reached the forefront of signal transduction research. Regulation of this lipid kinase, its functions, its effectors, in short its entire signaling network, has been extensively studied. PI3K inhibitors are frequently used in biochemistry and cell biology. In addition, many pharmaceutical companies have launched drug‐discovery programs to identify modulators of PI3Ks. Despite these efforts and a fairly good knowledge of the PI3K signaling network, we still have only a rudimentary picture of the signaling dynamics of PI3K and its lipid products in space and time. It is therefore essential to create and use novel biological and chemical tools to manipulate the phosphoinositide signaling network with spatial and temporal resolution. In this review, we discuss the current and potential future tools that are available and necessary to unravel the various functions of PI3K and its isoforms.