Computation of Stability Delay Margin of Time-Delayed Generator Excitation Control System with a Stabilizing Transformer

This paper investigates the effect of time delays on the stability of a generator excitation control system compensated with a stabilizing transformer known as rate feedback stabilizer to damp out oscillations. The time delays are due to the use of measurement devices and communication links for data transfer. An analytical method is presented to compute the delay margin for stability. The delay margin is the maximum amount of time delay that the system can tolerate before it becomes unstable. First, without using any approximation, the transcendental characteristic equation is converted into a polynomial without the transcendentality such that its real roots coincide with the imaginary roots of the characteristic equation exactly. The resulting polynomial also enables us to easily determine the delay dependency of the system stability and the sensitivities of crossing roots with respect to the time delay. Then, an expression in terms of system parameters and imaginary root of the characteristic equation is derived for computing the delay margin. Theoretical delay margins are computed for a wide range of controller gains and their accuracy is verified by performing simulation studies. Results indicate that the addition of a stabilizing transformer to the excitation system increases the delay margin and improves the system damping significantly

A computer-based testing system to evaluate protective relays as a tool in power system protection education

Teaching power system relaying is a fundamental issue in a power system high-level course. However, for an effective instruction of this topic an experience with real equipments can be considered as fundamental. To achieve this purpose, in this paper a new approach for the practical learning of power system relaying is presented. This consists of a computer-based testing system of relay-operating characteristic. Different relay types and developed specific software are also an important piece of the laboratory practice. Using this system it is possible to understand the performance and limitations of different protective relay systems and to test a real relay disoperation. The benefit of using this system is not available through traditional lectures and textbooks

DESIGN, LOCATION, ORGANIZATION, AND INDUSTRIAL MANAGEMENT OF A MUNITIONS PLANT

Abstract not availabl

Stability analysis of time-delayed DC motor speed control system

WOS: 000322743700007In this paper, the stability of time-delayed DC motor speed control systems is analyzed. The measurement devices and communication links used by networked control systems, cause a significant amount of time delays. The stability boundary of the system in terms of the time delay is theoretically determined and an expression is obtained to compute the delay margin in terms of system parameters. The delay margin is defined as the maximum amount of time delay for which the DC motor speed control system is marginally stable. The results indicate that the system becomes unstable if the time delay exceeds the delay margin at a given set of parameters. Theoretical delay margin results are verified using the time-domain simulations of MATLAB/Simulink

TO EXAMINE THE ROLE OF HYPOXIA ON ANTI-TUMOUR IMMUNITY

Inhibition of tumor angiogenesis has been extensively utilized in the treatment of metastatic colorectal cancer and renal cell carcinoma. Complete disruption of tumor angiogenesis results in hypoxia which promotes tumor metastasis and treatment resistance. Although angiogenesis inhibitors are successful to some extent, majority of patients experience the recurrence and acquired resistance. Spatial and temporal changes in tumor microenvironment sculpt the anti-tumor immune response. However, little is known how tumor oxygenation and vessel normalization in vivo influence immune infiltration in YUMMER melanoma tumors. We hypothesized that tumor vessel structure implicates in immune cell composition in melanoma. Therefore, we utilized a previously well-defined mouse model which targets one copy of Phd2 gene. Haplodeficiency of Phd2 normalizes the endothelial alignment and improves pericyte coverage of blood vessels, thereby increasing tumor perfusion and oxygenation. We demonstrated that mitigation of “true” hypoxia through blood vessel normalization improves anti-tumor immunity, thereby delaying tumor growth. In addition, our study highlighted that disruption of hypoxia using Phd2 haplodeficient mouse model re-shaped tumor microenvironment through improved CD4+ and CD8+ T cell infiltration, recruitment of pro-inflammatory macrophages, and diminished infiltration of PD-L1hi anti-inflammatory macrophages. Subsequently, tumor growth is delayed in a T cell dependent manner. In conclusion, Phd2 haplodeficiency restores tumor oxygenation and enhances anti-tumor immune cell infiltration in melanoma tumors.Anjiojenez inhibitörleri metastatik kolorektal kanser ve renal hücreli karsinoma tedavisinde çok önemli bir yer edinmektedir. Fakat tümör anjiojenezinin tamamen ortadan kaldırılması ile tümör hipoksisi oluşmaktadır. Solid tümörlerde hipoksinin uzak metastazda ve anti-kanser tedavilere dirençte önemli bir rol aldığı bilinmektedir. Buna istinaden anjiojenez inhibitörü kullanan pek çok kanser hastasında da anjijenez inhibitörlerinin etkinliği kısıtlı kalmakta olup tedaviye karşı kazanılmış direnç ve hastalık rekürrensi en sık karşılaşılan problemlerden biridir. Tümör mikroçevresindeki lokalize ve zamansal değişimler anti- tümör immün yanıtları şekillendirmektedir. Buna rağmen in vivo tümör oksijenizasyonunun ve damar normalizasyonunun melanomaya karşı immün yanıtı nasıl etkilediği tam olarak anlaşılamamıştır. Çalışmaya damar yapısının YUMMER melanoma modelinde immün kompozisyonu etkilediği hipotezi ile başladık. Bunu gösterebilmek için Phd2 haplodefektli fareleri kullandık. Bu defekt sayesinde damarlardaki perisit hücre ile çevrili olma oranı artmış ve endotel hücre dizilimi normalize olmuştur. Sonuç olarak oksijenizasyon artmıştır. Artan oksijenizasyonu takiben CD4+ ve CD8+ T hücre infiltrasyonu ve pro-inflamatuar makrofaj infiltrasyonunun arttığı görülmüştür. Bunun yanında yüksek oranda PD-L1 eksprese eden anti-inflamatuar makrofaj infiltrasyonu da azalmıştır. Bu bulgularla paralel olarak tümör büyümesi T hücre bağımlı bir mekanizma ile yavaşlamıştır. Sonuç olarak fare melanoma modelinde Phd2 haplodefekti tümör oksijenizasyonunu restore etmekte ve anti-tümör immün infiltrasyonu iyileştirmektedir

Computation of time delay margin for power system small-signal stability

WOS: 000271564900004With the extensive use of phasor measurement units (PMU) in the wide-area measurement/monitoring systems (WAMS), time delays have become unavoidable in power systems. This paper presents a direct and exact method to Compute the delay margin of power systems with single and commensurate time delays. The delay margin is the maximum amount Of time delay that the system can tolerate before it becomes unstable fora given operating point. First, without using any approximation or substitution, the transcendental characteristic equation is converted into a polynomial without the transcendentality such that its real roots coincide with the imaginary roots of the characteristic equation exactly. The resulting polynomial also enables us to easily determine the delay dependency of the system stability and the sensitivities of crossing roots with respect to time delay. Then, an expression in terms of system parameters and imaginary root of the characteristic equation is derived for computing the delay margin. The proposed method is applied to a single-machine-infinite bus (SMIB) power system with an exciter. Delay margins are computed for a wide range of system parameters including generator mechanical power, damping and transient reactance, exciter gain, and transmission line reactance. The results indicate that the delay margin decreases as the mechanical power, exciter gain and line reactance increase while it increases with increasing generator transient reactance Additionally, the relationship between the delay margin and generator damping is found be relatively complex. Finally, the theoretical delay margin results are validated using the time-domain simulations of Matlab. Copyright (C) 2008 John Wiley & Sons, Ltd

Effects of algebraic singularities on the voltage dynamics of differential-algebraic power system model

WOS: 000259985500001Voltage stability analysis of differential-algebraic equation (DAE) power system model is more complicated than for systems described by ordinary differential equations (ODEs). In addition to unstable equilibria, algebraic singularity plays a crucial role in assessing the voltage stability. This paper explores the algebraic structure and singularities of the DAE model to investigate its influence on the voltage stability. Singular points are identified at various load levels and are illustrated together with the equilibria using nose Curves. Then, at a given load level, the constraint manifold is decomposed into the voltage casual regions and singular points connecting them. Time-domain simulations initiated in the vicinity Of Singular points are performed to determine how singular points affect system dynamics. It is shown that depending on the relative location of initial points with respect to singular points, trajectories of bus voltages may settle to an infeasible low voltage stable equilibrium point, which may cause a further disturbance in the system leading a voltage stability problem. Copyright (C) 2007 John Wiley & Sons, Ltd

Realization of Power Electronic Converter Based DC Motor Speed Control Methods Using MATLAB/Simulink

WOS: 000264256800005The MATLAB/Simulink realization of DC motor speed control methods is achieved here by controlling the voltage applied to the armature circuit using various controlled and uncontrolled power electronic converters. The power electronic converters used in simulation models include full-bridge diode rectifier, half controlled rectifier and pulse width modulated (PWM) chopper. These Simulation models are developed as a part of a software laboratory to support and enhance undergraduate electric machinery courses at Nigde University, Turkey

İman ve suç ilişkisi

Kalkınmakta olan bir ülke konumunda olan Ülkemiz insanlarının daha yüksek bir yaşam seviyesine ulaştırılması hepimizin ortak arzusudur. Bu amacın gerçekleştirilmesine dönük olarak Devletimiz tarafından yatırımların geliştirilmesi ve yeni istihdam alanlarının oluşturulması amacıyla geliştirilen Teşvik Tedbirleri ve bu tedbirlerden Yatırım İndirimi çalışmamızın ana konusunu teşkil etmektedir. Yatırım İndirimi ile öngörülen amaç, Genel Kalkınma Planı ve Yıllık Programlarda yer alan bölge ve sektörlerde yapılacak yatırım harcamalarının, belli ölçüde vergiye tabi kazançtan düşülmek suretiyle yatırımların artmasının ve bu yolla kalkınmanın hızlanmasının sağlanmasıdır. 1963 yılından itibaren Kalkınma Planlarıyla gündeme gelmeye başlamış ve 202 sayılı Kanunla vergi sistemimize girmiş olan Teşvik Tedbirlerinden Yatırım İndirimi, yatırımcı kurumlar açısından yatırıma yöneltici etkenlerden en önemlisi olmuş ve özellikle 1.1.1999 tarihinde yürürlüğe giren 4369 sayılı Kanunla kurumlar için yatırıma yöneltici etkin bir unsur halini almıştır. 1998 yılında yasallaşan ve 1.1.1999 tarihinde yürürlüğe giren "Vergi Reformu Kanunu" nun yatırım indirimi hükümleri yatırımcı kurumlar açısından çeşitli imkanları beraberinde getirmektedir. Bu hükümlere göre yatırım indiriminin kurum kazancı açısından etkisi çalışmamızda ortaya konmaya çalışılmıştır. Ayrıca 2000 yılına ve daha sonraki yıllara ilişkin olarak Gelir Vergisi Kanunu'nun 94. maddesinde yapılan değişiklikle yatırım indiriminin stopaja tabi olduğu kanun metninde açıkça belirtilmiştir. Böylece Kurumlar Vergisi oranı %25 ten %30'a çıkarılmasına rağmen Yatırım İndirimi sayesinde Kurumlar üzerinde bulunan vergi yükü %44 lerden %33'e indirilmiştir. Bu ise yatırımcı kurumlar için yatırıma yöneltici gerçekten önemli bir teşvik unsurudur. Yukarıda da değinildiği üzere, Teşvik Tedbirleri ve bu tedbirlerden biri olarak Yatırım İndirimi ülkelerin kalkınmasında önemli bir uygulama olarak karşımıza çıkmakta ve sonuçları itibariyle yeni yatırımlara yol açmaktadır.It is main desire of everyone to increase the living standart of the people who lives in our country which can be assumed as developing country. In conjunction to this desire, our government officials are planning & preparing new incentive counter measures. In this study, we tried to analyse these counter measures and mainly concerned ourselves in investment reductions When we say "investment reduction" we are concerning General Developing Plans, investment plans for areas and sectors on annual basis, taxation plans including how to invest taxes into development. These plans were started in 1963 and were fixed as the rule numbered 202 investment ant development taxation law. However they were further developed and revised at the beginning of 1999 via the number 4369 Taxation Law in The Turkish Law. Law established in 1998 and at the beginning of 1999 led to a new taxation system called the "Taxation Reform Law" provide some opportunities for the establihments.. The effects of rules of this law on the profit of establishment is tried to be investigated in this study. Furthermore, as form 2000 onwards new changes leading to invesment reductions where it has been dependent no stoppage at source were revised in the income taxation law number 94. Thus, although the new establishment taxation caused to increase tax ratio from 25% to 30%, it became posible to reduce tax charge on the establishments from 44% to 33% troughout investment. This game investment open establishments incitement towards new investments. As it is mentioned above we can say that incentive courter measures are a neccesary for the desire of strengthening the standart of our nation and giving us opportunities for further investments