Grid Voltage Sensorless Single-Phase Half-Bridge Active Filter and DC Bus Voltage Regulation

In this paper, a method is presented for the control of grid voltage sensorless single-phase half-bridge shunt active power filter to reduce the grid current harmonics of low-power single-phase non-linear loads. The proposed system forces the grid current to be sinusoidal without sensing and processing the grid voltage on the line. For this reason, instead of grid voltage the load current is processed by using self-tuning filter to generate reference grid current to eliminate current harmonic distortions. In order to design a low-cost system, a half-bridge voltage source converter is used to reduce driver circuits. In addition, the switching losses are also reduced by employing half-bridge voltage source converter, where only two switches are used. The imbalance voltages are also successfully eliminated on the DC-side capacitors. The performance of the proposed system is verified by using a real-time platform, and experimental results are presented to verify the effectiveness of the proposed system in this study

İnci Pastanesi 50 yaşında

Taha Toros Arşivi, Dosya No: 112-Pastahaneler, Bozacılar, Gazozcular, Börekçiler, Turşucular, Sucularİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

The role of logo design in creating brand emotion: A semiotic comparison of the Apple and IBM logos

Thesis (Master)--Izmir Institute of Technology, Industrial Design, Izmir, 2006Includes bibliographical references (leaves: 111-122)Text in English; Abstract: Turkish and Englishix, 117 leavesThis thesis explains the role of logo design in creating brand emotion as a comparative analysis of Apple and IBM using the semiotic theory of Charles Morris.These research reports the results of the comparisons, and in the light of the results reaches conclusions about the emotional value of a logo to a company and the way it affects their consumers. The visual sign elements of IBM.s monochromatic, straight, striped-block letters versus Apple.s rainbow coloured, rounded, and partially bitten apple have been compared syntactically, semantically, and pragmatically. A well designed emotional logo becomes a visual shorthand for the meanings attached to it, and therefore it influences consumers to be receptive to the brand message and effects consumers emotionally, making them exhibit extreme loyalty to the brand. They invoke emotion and brand not only the company, but the customer as well. This thesis, using semiotics, shows the importance of designing logos to create an emotional, even subconscious, connection with consumers

STRUCTURE AND RELIEF OF ALBANIA

ALBANIA, is a European country situated in the Balkan Peninsula. The west side is bordered with the southeastern costs of Adriatic Sea . Albania has borders with MONTENEGRO in the North KOSOVO and SYRBIA in the northeast,MACEDONIA in the east , GREECE in the south - southeast.Area 28. 742 km2 , .Capital city is TIRAN.Shkodra ( Shkoder ), Durres , Albania ( Durres ), Elbasan, Korca ( Korce ), Vlora (Vlore ), Gjirokastra (Gjirokaster), are the major cities.The population is 3,194,972 according to 2010 census results, respectively. The rateof Albanian population is 95 . 3 %, 2, 5 % gypsies, 1,8 is Greek, 0.14 is Macedonian and Kosovo people.Albania is a mountainous country. The mountains are included in the Alpine Orogeny System. Albanian Alps mountain ranges in the North , east , south - known as the Dinaric Alps. These different orographic and tectonic nomenclature extensions on developments in different directions.The main factor in determining the structure and relief of Albania on the basis ofthe Alpine Orogeny, and epyrogenyc Movements related to that. The presence of Plato and lowlands is related to them.The presence of high mountains ( the Shar Mountains, 2764 m, etc. ), by the rivers around here has deep breach. Aspects of the main stretch of rivers, but some exceptional cases, the south-east, north-west is true. This stretch, depending on the systems developed in the fold is not a coincidence.The country from east to west elevation is gradually lowered, Adriatic Sea coast isthe transition towards the plains. Land in the country about 1 / 3', which corresponds to the formation and development of the plains, and even the whole structure and relief of the country's present - day tectonic, isostatic and eustaticcontrols on movements.The details of the issue is given in the main text relatively

Proportional-integral and proportional-resonant based control strategy for PUC inverters

In this paper, a proportional-integral (PI) and proportional-resonant (PR) based control strategy is proposed for packed-U-cell (PUC) inverters. In the conventional PI-PI based control strategy, while the first PI regulates the DC capacitor voltage, the second PI regulates the AC load current. However, it is shown that the second PI cannot guarantee zero tracking error in the load current. The main reason of this comes from the fact that PI controllers are not able to achieve zero tracking error for the AC signals. Also, in an attempt to reduce the tracking error by tuning PI gains distorts the load current. In this study, a PI-PR based control strategy is obtained by replacing the second PI by a PR controller. The performances of both PI-PI and PI-PR control methods have been compared. It is shown that the load current to tracks its reference in all circumstances provided that the inverter current reference is generated accurately. Computer simulations are conducted to show the steady-state and dynamic performances of both control methods

Three-level hysteresis current control strategy for three-phase four-switch shunt active filters

In this study, a three-level hysteresis current-control (HCC) strategy is proposed for three-phase four-switch shunt active power filters. The four-switch topology which utilises four switching devices together with two series connected capacitors is able to reduce the cost, switching losses and improve the reliability of system. In this topology, when the current control of phases A and B is achieved successfully, the current control of phase C which is connected to the midpoint of the series connected capacitors is achieved automatically. The current control is achieved by using a three-level HCC strategy. An important consequence of using this control strategy is that it enables access to the zero level of the input voltage of active filter so that a switching device is only switched when the current error is negative, while it remains off when the current error is positive. Furthermore, the imbalance in the capacitor voltages is eliminated by adding a feedback term (the difference in the capacitor voltages multiplied by a suitable gain) to the current control. The proposed control strategy offers a reduced switching frequency, losses and cost. The steady-state and dynamic performance of the proposed control strategy is verified through simulations and experimental studies

Effect of cellulase treatment of long fiber fraction on strength properties of recycled corrugated medium

It is a well-known fact that the physical strength properties of fibers decrease with recycling. The aim of this study was to investigate the positive effect of using commercial cellulase enzymes on the physical strength properties of corrugated medium. The long fiber fraction of pulp is the most appropriate application point of a cellulase enzyme. Therefore, the pulp used in this research has been obtained at fractionation screen levels of modern Karton paper mill Turkey. The long-fiber fraction of the pulp for corrugated medium was pre-treated with four different commercial enzymes, Roglyr Bio 1537, Maximyze 2520, Benstone and Bensoft Plus. The handsheets for physical testing were prepared after blending of beaten long-fiber and unbeaten short-fiber fractions. The obtained test results have indicate that the application of enzyme on appropriate fiber fraction have positive effects on the strength properties of the corrugated medium. The short span compression test is one of most important strength properties of corrugated board and increase from 8.41 to 20.5% with enzymatic pre-treatment and beating of the long fiber fraction.Key words: Corrugated medium, enzymatic pre-treatment, cellulase, long-fiber fraction, paper strength properties, short span compression

Time-Varying and Constant Switching Frequency-Based Sliding-Mode Control Methods for Transformerless DVR Employing Half-Bridge VSI

This paper presents time-varying and constant switching frequency based sliding-mode control (SMC) methods for three-phase transformerless dynamic voltage restorers (TDVRs) which employ half-bridge voltage source inverter. An equation is derived for the time-varying switching frequency. However, since the time-varying switching frequency is not desired in practice, a smoothing operation is applied to the sliding surface function within a narrow boundary layer with the aim of eliminating the chattering effect and achieving a constant switching frequency operation. The control signal obtained from the smoothing operation is compared with a triangular carrier signal to produce the pulse width modulation signals. The feasibility of both SMC methods has been validated by experimental results obtained from a TDVR operating under highly distorted grid voltages and voltage sags. The results obtained from both methods show excellent performance in terms of dynamic response and low total harmonic distortion (THD) in the load voltage. However, the constant switching frequencybased SMC method not only offers a constant switching frequency at all times and preserves the inherent advantages of the SMC, but also leads to smaller THD in the load voltage than that of time-varying switching frequency-based SMC method

Optimized Sliding Mode Control to Maximize Existence Region for Single-Phase Dynamic Voltage Restorers

This paper presents an optimized sliding mode control (SMC) strategy to maximize existence region for single-phase dynamic voltage restorers. It is shown analytically that there exists an optimum sliding coefficient which enlarges the existence region of the sliding mode to its maximum. Also, it is pointed out that the optimum sliding coefficient improves the dynamic response. In addition, a double-band hysteresis control which ensures the switching of a transistor in the voltage source inverter during a half-cycle while it remains either on or off in the other half cycle is used to mitigate the switching frequency. The theoretical considerations and analytical results are verified through computer simulations and experimental results. Simulation and experimental results show that the proposed SMC strategy not only compensates the undesired voltage disturbances and maintains the load voltage at desired level with low total harmonic distortion, but also exhibits fast dynamic response and operates at reasonably low switching frequency

Detection of Grid Voltage Anomalies via Broadband Subspace Decomposition

Due to the increase of sensitive loads on the mains power grid, measurement and monitoring of the power quality (PQ) have become an important factor for both consumers and operators. As is well-known, PQ problems occur in a very short time period with specific characteristics. In transmission or distribution systems, power quality data are collected from monitoring devices such as digital fault recorders, power quality and dynamic system monitors, etc. The recorded data has to be analysed in order to understand system anomalies. These anomalies may be due to sources of broadband noise. In this study, we employ broadband subspace decomposition, using polynomial eigenvalue decomposition, to detect these anomalies. Results demonstrate that this method may be considered as a new and effective tool for measurement and monitoring of PQ problems