Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 43397

Electrical and Computer Engineering

Effects of Body Bias Variation on the Performance of a Class AB Operational Amplifier
This paper presents the effect of body bias variation on the performance of a two stage Class AB Folded Cascode operational amplifier in 22nm FD-SOI(fully depleted silicon on insulator) technology. The body bias is varied on each of the opamp (operational amplifier) building block and its impact on the overall op-amp performance is observed. Finally the results of the op-amp with body bias and without body bias are compared. The primary output parameters measured are open loop gain, unity gain bandwidth, settling time (12 bit), output range, phase margin and power consumption. While most of the parameters remain nearly constant or do not change much, there is a tuning range of 6dB for open loop gain, the input range of 325mV can be shifted by around 110mV and settling time can be varied by 15%.
A Design of 400 MHz Voltage-Controlled Oscillator and Power Amplifier for UHF Transceiver Using Direct Modulation Transmitter Architecture
This paper presents the design of the RF transmitter of UHF Transceiver using 180 nm CMOS technology at 400 MHz. The design of RF transmitter in this paper using direct modulation architecture which includes VCO, buffer, divider and class AB of the power amplifier. The results of the PA are maximum output power of 12.9 dBm, OP1dB of 11.7 dBm, PAE of 6.79 % with 3 bits power control and including LDO, bonding wire effect. The architecture using of VCO in this paper was quadrature LC which created both I and Q signal at 1.66 GHz with only 1.25 degree mismatch and including 3 bit frequency control. Finally, the RF transmitter was connected with 13 dBm output power while consuming 64.8 mW with 3.3 V supply voltage.
Low Power, Highly Linear, Wideband LNA in Wireless SOC
In this paper a highly linear CMOS low noise amplifier (LNA) for ultra-wideband (UWB) applications is proposed. The proposed LNA uses a linearization technique to improve second and third-order intercept points (IIP3). The linearity is cured by repealing the common-mode section of all intermodulation components from the cascade topology current with optimization of biasing current use symmetrical and asymmetrical circuits for biasing. Simulation results show that maximum gain and noise figure are 6.9dB and 3.03-4.1dB over a 3.1–10.6 GHz, respectively. Power consumption of the LNA core and IIP3 are 2.64 mW and +4.9dBm respectively. The wideband input impedance matching of LNA is obtained by employing a degenerating inductor (|S11|
A Low Phase Noise CMOS LC Oscillator with Tail Current-Shaping
In this paper, a circuit topology of voltage-controlled oscillators (VCO) which is suitable for ultra-low-phase noise operations is introduced. To do so, a new low phase noise cross-coupled oscillator by using the general topology of cross-coupled oscillator and adding a differential stage for tail current shaping is designed. In addition, a tail current shaping technique to improve phase noise in differential LC VCOs is presented. The tail current becomes large when the oscillator output voltage arrives at the maximum or minimum value and when the sensitivity of the output phase to the noise is the smallest. Also, the tail current becomes small when the phase noise sensitivity is large. The proposed circuit does not use extra power and extra noisy active devices. Furthermore, this topology occupies small area. Simulation results show the improvement in phase noise by 2.5dB under the same conditions and at the carrier frequency of 1 GHz for GSM applications. The power consumption of the proposed circuit is 2.44 mW and the figure of merit (FOM) with -192.2 dBc/Hz is achieved for the new oscillator.
Nine-Level Shunt Active Power Filter Associated with a Photovoltaic Array Coupled to the Electrical Distribution Network
The use of more and more electronic power switches with a nonlinear behavior generates non-sinusoidal currents in distribution networks, which causes damage to domestic and industrial equipment. The multi-level shunt power active filter is subsequently shown to be an adequate solution to the problem raised. Nevertheless, the difficulty of adjusting the active filter DC supply voltage requires another technology to ensure it. In this article, a photovoltaic generator is associated with the DC bus power terminals of the active filter. The proposed system consists of a field of solar panels, three multi-level voltage inverters connected to the power grid and a non-linear load consisting of a six-diode rectifier bridge supplying a resistive-inductive load. Current control techniques of active and reactive power are used to compensate for both harmonic currents and reactive power as well as to inject active solar power into the distribution network. An algorithm of the search method of the maximum power point of type Perturb & Observe is applied. Simulation results of the system proposed under the Matlab/Simulink environment shows that the performance of control commands that reassure the solar power injection in the network, harmonic current compensation and power factor correction.
On-Chip Ku-Band Bandpass Filter with Compact Size and Wide Stopband
This paper presents a design of a microstrip bandpass filter with a compact size and wide stopband by using 0.15-μm GaAs pHEMT process. The wide stop band is achieved by suppressing the first and second harmonic resonance frequencies. The slow-wave coupling stepped impedance resonator with cross coupled structure is adopted to design the bandpass filter. A two-resonator filter was fabricated with 13.5GHz center frequency and 11% bandwidth was achieved. The devices are simulated using the ADS design software. This device has shown a compact size and very low insertion loss of 2.6 dB. Microstrip planar bandpass filters have been widely adopted in various communication applications due to the attractive features of compact size and ease of fabricating. Various planar resonator structures have been suggested. In order to reach a wide stopband to reduce the interference outside the passing band, various designs of planar resonators have also been submitted to suppress the higher order harmonic frequencies of the designed center frequency. Various modifications to the traditional hairpin structure have been introduced to reduce large design area of hairpin designs. The stepped-impedance, slow-wave open-loop, and cross-coupled resonator structures have been studied to miniaturize the hairpin resonators. In this study, to suppress the spurious harmonic bands and further reduce the filter size, a modified hairpin-line bandpass filter with cross coupled structure is suggested by introducing the stepped impedance resonator design as well as the slow-wave open-loop resonator structure. In this way, very compact circuit size as well as very wide upper stopband can be achieved and realized in a Roger 4003C substrate. On the other hand, filters constructed with integrated circuit technology become more attractive for enabling the integration of the microwave system on a single chip (SOC). To examine the performance of this design structure at the integrated circuit, the filter is fabricated by the 0.15 μm pHEMT GaAs integrated circuit process. This pHEMT process can also provide a much better circuit performance for high frequency designs than those made on a PCB board. The design example was implemented in GaAs with center frequency at 13.5 GHz to examine the performance in higher frequency in detail. The occupied area is only about 1.09×0.97 mm2. The ADS software is used to design those modified filters to suppress the first and second harmonics.
Ice Load Measurements on Known Structures Using Image Processing Methods
The study uses a new method based on image analyses and structure information to detect accumulated ice on known structures. The icing of marine vessels and offshore structures causes significant reductions in their efficiency and creates unsafe working conditions. Image processing methods are used to measure ice load automatically. Most image processing methods are developed based on captured image analyses. Using the proposed method, ice loads on structures are calculated by defining structure coordinates and processing captured images. A sample structure is designed using 9 cylindrical bars as the experimental setup. Unsymmetrical ice is accreted on the structure using a subzero cold room. Camera intrinsic and extrinsic parameters are used to define structure coordinates in the image coordinate system according to the camera location and angle. Thresholding method is applied on captured images to detect iced structure in a binary image. Combining the binary image information and the structure coordinate information, the ice thickness of each element is calculated. The ice thicknesses of structure elements are calculated the averaging of ice diameters in different camera views. Comparison between the ice load measurement in this method and the actual ice load shows a good agreement with an acceptable 5-20 percent margin of error. The method can be applied to complex structures using the structure coordinates and the camera coordinate with respect to a reference coordinate system.
Method for Assessment of Street Lighting Systems Lightning Susceptibility
Street and area lighting systems can be damaged by lightning activity in their vicinity. This damage can occur as a result of a direct strike to a pole or luminaire, surges resulting from a strike to power lines feeding the circuits powering the lighting system, and induced surges on underground power lines (this is the most likely scenario). The session addresses each of these scenarios considering the cases where there is no lightning and surge protection provided on the poles and with varying levels of surge protection installed. In order to provide protection against direct strikes, a lightning protection system should be installed must this is not often the case even if a lighting pole acts as a lightning rod. Most of the problems will arise on other poles from surges generated either by the pole hit by lightning (this one is lost). As a result, this discussion focuses mainly on surges and the risk of loss of service to the public (R2) in accordance with IEC Standard 62305-2, Edition 2. The analysis will focus on determining the sensitivity of lighting systems due to overvoltages and the statistical benefit to survivability gained by the installation of surge protective measures. Specific examples are discussed, based on a comparison of systems incorporating high-intensity discharge (HID) lamps versus lighting systems incorporating LED technologies. The assessment also addresses an economic analysis based on the cost of the damaged material and expenses related to the repairs required to restore the required service. Based on the assumptions made in the examples, a simplified method has been developed to determine the benefit of an assessment based on the lightning ground flash density, type of technology used, and length of cabling of lighting system.
Micromechanical Analysis of Interface Properties Effects on Transverse Tensile Response of Fiber-Reinforced Composites
A micromechanical analysis of the influence of fiber-matrix interface fracture properties on the transverse tensile response of fiber-reinforced composite is investigated. Augmented finite element method (AFEM) is used to provide high-fidelity damage initiation and propagation along the micromechanical analysis. Effects of fiber volume fraction and fiber shapes are also studies in representative volume elements (RVE) to capture the stochastic behavior of the composite under loading. In addition, defects and voids influence on the composite response are investigated in micromechanical analysis. The results reveal that the response of RVE with constant interface properties overestimates the composite transverse strength. It is also seen that the damage initiation and propagation locations are controlled by the distributions of fracture properties, fibers’ shapes, and defects.
The Use of the Limit Cycles of Dynamic Systems for Formation of Program Trajectories of Points Feet of the Anthropomorphous Robot
The movement of points feet of the anthropomorphous robot in space occurs along some stable trajectory of a known form. A large number of modifications to the methods of control of biped robots indicate the fundamental complexity of the problem of stability of the program trajectory and, consequently, the stability of the control for the deviation for this trajectory. Existing gait generators use piecewise interpolation of program trajectories. This leads to jumps in the acceleration at the boundaries of sites. Another interpolation can be realized using differential equations with fractional derivatives. In work, the approach to the synthesis of generators of program trajectories is considered. The resulting system of nonlinear differential equations describes a smooth trajectory of movement having rectilinear sites. The method is based on the theory of an asymptotic stability of invariant sets. The stability of such systems in the area of localization of oscillatory processes is investigated. The boundary of the area is a bounded closed surface. In the corresponding subspaces of the oscillatory circuits, the resulting stable limit cycles are curved having rectilinear sites. The solution of the problem is carried out by means of synthesis of a set of the continuous smooth controls with feedback. The necessary geometry of closed trajectories of movement is obtained due to the introduction of high-order nonlinearities in the control of stabilization systems. The offered method was used for the generation of trajectories of movement of point’s feet of the anthropomorphous robot. The synthesis of the robot's program movement was carried out by means of the inverse method.
Low Trigger Voltage Silicon Controlled Rectifier Stacking Structure with High Holding Voltage for High Voltage Applications
A SCR stacking structure is proposed to have improved Latch-up immunity. In comparison with conventional SCR (Silicon Controlled Rectifier), the proposed Electrostatic Discharge (ESD) protection circuit has a lower trigger characteristic by using the LVTSCR (Low Voltage Trigger) structure. Also the proposed ESD protection circuit has improved Holding Voltage Characteristic by using N-stack technique. These characteristics enable to have latch-up immunity in operating conditions. The simulations are accomplished by using the Synopsys TCAD. It has a trigger voltage of 8.9V and a holding voltage of 1.8V in a single structure. And when applying the stack technique, 2-stack has the holding voltage of 3.8V and 3-stack has the holding voltage of 5.1 V.
K-Means Based Matching Algorithm for Multi-Resolution Feature Descriptors
Matching high dimensional features between images is computationally expensive for exhaustive search approaches in computer vision. Although the dimension of the feature can be degraded by simplifying the prior knowledge of homography, matching accuracy may degrade as a tradeoff. In this paper, we present a feature matching method based on k-means algorithm that reduces the matching cost and matches the features between images instead of using a simplified geometric assumption. Experimental results show that the proposed method outperforms the previous linear exhaustive search approaches in terms of the inlier ratio of matched pairs.
Rotor Side Speed Control Methods Using MATLAB/Simulink for Wound Induction Motor
In recent advancements in electric machine and drives, wound rotor motor is extensively used. The merit of using wound rotor induction motor being controlling speed/torque characteristics by inserting external resistance. Wound rotor induction motor can be used in the cases such as (a) low inrush current, (b) load requiring high starting torque, (c) lower starting current is required, (d) loads having high inertia, and (e) gradual built up of torque. Examples include conveyers, cranes, pumps, elevators and compressors. This paper includes speed control of wound induction motor using MATLAB/Simulink for rotor resistance and slip power recovery method. The characteristics of these speed control method hence analyzed.
Computer-Aided Teaching of Transformers for Undergraduates
In the era of technological advancement, use of computer technology has become inevitable. Hence it has become the need of the hour to integrate software methods in engineering curriculum as a part to boost pedagogy techniques. Simulations software is a great help to graduates of disciplines such as electrical engineering. Since electrical engineering deals with high voltages and heavy instruments, extra care must be taken while operating with them. The viable solution would be to have appropriate control. The appropriate control could be well designed if engineers have knowledge of kind of waveforms associated with the system. Though these waveforms can be plotted manually, but it consumes a lot of time. Hence aid of simulation helps to understand steady state of system and resulting in better performance. In this paper computer, aided teaching of transformer is carried out using MATLAB/Simulink. The test carried out on a transformer includes open circuit test and short circuit respectively. The respective parameters of transformer are then calculated using the values obtained from open circuit and short circuit test respectively using Simulink.
Modern Pedagogy Techniques for DC Motor Speed Control
Based on a survey conducted for second and third year students of the electrical engineering department at Maharishi Markandeshwar University, India, it was found that around 92% of students felt that it would be better to introduce a virtual environment for laboratory experiments. Hence, a need was felt to perform modern pedagogy techniques for students which consist of a virtual environment using MATLAB/Simulink. In this paper, a virtual environment for the speed control of a DC motor is performed using MATLAB/Simulink. The various speed control methods for the DC motor include the field resistance control method and armature voltage control method. The performance analysis of the DC motor is hence analyzed.
Finite Element Analysis of a Modular Brushless Wound Rotor Synchronous Machine
This paper presents a comparative study of different modular brushless wound rotor synchronous machine (MB-WRSM). The goal of the study is to highlight the structure which offers the best fault tolerant capability and the highest output performances. The fundamental winding factor is calculated by using the method based on EMF phasors as a significant criterion to select the preferred number of phases, stator slots, and poles. With the limited number of poles for a small machine (3.67kW/7000rpm), 15 different machines for preferred phase/slot/pole combinations are analyzed using two-dimensional (2-D) finite element method and compared according to three criteria: torque density, torque ripple and efficiency. The 7phase/7slot/6pole machine is chosen with the best compromise of high torque density, small torque ripple (3.89%) and high nominal efficiency (95%). This machine is then compared with a reference design surface permanent magnet synchronous machine (SPMSM). In conclusion, this paper provides an electromagnetic analysis of a new brushless wound-rotor synchronous machine using multiphase non-overlapping fractional slot double layer winding. The simulation results are discussed and demonstrate that the MB-WRSM presents interesting performance features, with overall performance closely matching that of an equivalent SPMSM.
Optimizing Approach for Sifting Process to Solve a Common Type of Empirical Mode Decomposition Mode Mixing
Empirical mode decomposition (EMD), a new data-driven of time-series decomposition, has the advantage of supposing that a time series is non-linear or non-stationary, as is implicitly achieved in Fourier decomposition. However, the EMD suffers of mode mixing problem in some cases. The aim of this paper is to present a solution for a common type of signals causing of EMD mode mixing problem, in case a signal suffers of an intermittency. By an artificial example, the solution shows superior performance in terms of cope EMD mode mixing problem comparing with the conventional EMD and Ensemble Empirical Mode decomposition (EEMD). Furthermore, the over-sifting problem is also completely avoided; and computation load is reduced roughly six times compared with EEMD, an ensemble number of 50.
The Effect of Power of Isolation Transformer on the Lamps in Airfield Ground Lighting Systems
To study the impact of the amount and volume of power of isolation transformer on the lamps in airfield Ground Lighting Systems. A test was conducted in Persian Gulf International Airport, This airport is situated in the south of Iran and it is one of the most cutting-edge airports, the same one that owns modern devices. Iran uses materials and auxiliary equipment which are made by ADB Company from Belgium. Airfield ground lighting (AGL) systems are responsible for providing visual issue to aircrafts and helicopters in the runways. In an AGL system a great deal of lamps are connected in serial circuits to each other and each ring has its individual constant current regulators (CCR), which through that provide energy to the lamps. Control of lamps is crucial for maintenance and operation in the AGL systems. Thanks to the Programmable Logic Controller (PLC) that is a cutting-edge technology can help the system to connect the elements from substations and ATC (TOWER). For this purpose, a test in real conditions of the airport done for all element that used in the airport such as isolation transformer in different power capacity and different consuming power and brightness of the lamps. The data were analyzed with Lux meter and Multimeter. The results had shown that the increase in the power of transformer caused a significant increase in brightness. According to the Ohm’s law and voltage division, without changing the characteristics of the light bulb, it is not possible to change the voltage, just need to change the amount of transformer with which it connects to the lamps. When the voltage is increased, the current through the bulb has to increase as well, because of Ohm's law: I=V/R and I=V/R which means that if V increases, so do I increase. The output voltage on the constant current regulator emerges between the lamps and the transformers.
Evaluation of Colour Perception in Different Correlated Colour Temperature of LED Lighting
The perception of colour is a subjective experience which depends on age, gender, race, cultural and educational backgrounds, etc. of an individual. However, colour perception is also affected by the correlated colour temperature (CCT) of a light source which is considered as one of the most fundamental quantitative lighting characteristics. This study focuses on evaluating colour perception in different CCT of light emitting diodes (LED) lighting. The aim is to compare the inherent colours with the perceived colours under two CCT of ‘warm’ (2700K), and ‘cool’ (4000K) LED lights and to understand how different CTT affect the perception of a colour. Analysis and specifications of colour attributes are made with Natural Colour System (NCS) which is an international colour communication system. The outcome of the study reveals the possible tendencies for perceived colours under different illuminance levels of LED lighting.
Optimal Design of Submersible Permanent Magnet Linear Synchronous Motor Based Design of Experiment and Genetic Algorithm
Submersible permanent magnet linear synchronous motors (SPMLSMs) are electromagnetic devices, which can directly drive plunger pump to obtain the crude oil. Those motors have been gradually applied in oil fields due to high thrust force density and high efficiency. Since the force performance closely depends on the concrete structural parameters, the seven different structural parameters are investigated in detail. This paper presents an optimum design of an SPMLSM to minimize the detent force and maximize the thrust by using design of experiment (DOE) and genetic algorithm (GA). The three significant structural parameters (air-gap length, slot width, pole-arc coefficient) are separately screened using 27 1/16 fractional factorial design (FFD) to investigate the significant effect of seven parameters used in this research on the force performance. Response surface methodology (RSM) is well adapted to make analytical model of thrust and detent force with constraints of corresponding significant parameters and enable objective function to be easily created, respectively. GA is performed as a searching tool to search for the Pareto-optimal solutions. By finite element analysis, the proposed PMLSM shows merits in improving thrust and reducing the detent force dramatically.
Improved Traveling Wave Method Based Fault Location Algorithm for Multi-Terminal Transmission System of Wind Farm with Grounding Transformer
Due to rapid load growths in today’s highly electrified societies and the requirement for green energy sources, large-scale wind farm power transmission system is constantly developing. This system is a typical multi-terminal power supply system, whose structure of the network topology of transmission lines is complex. What’s more, it locates in the complex terrain of mountains and grasslands, thus increasing the possibility of transmission line faults and finding the fault location with difficulty after the faults and resulting in an extremely serious phenomenon of abandoning the wind. In order to solve these problems, a fault location method for multi-terminal transmission line based on wind farm characteristics and improved single-ended traveling wave positioning method is proposed. Through studying the zero sequence current characteristics by using the characteristics of the grounding transformer(GT) in the existing large-scale wind farms, it is obtained that the criterion for judging the fault interval of the multi-terminal transmission line. When a ground short-circuit fault occurs, there is only zero sequence current on the path between GT and the fault point. Therefore, the interval where the fault point exists is obtained by determining the path of the zero sequence current. After determining the fault interval, The location of the short-circuit fault point is calculated by the traveling wave method. However, this article uses an improved traveling wave method. It makes the positioning accuracy more accurate by combining the single-ended traveling wave method with double-ended electrical data. What’s more, a method of calculating the traveling wave velocity is deduced according to the above improvements (it is the actual wave velocity in theory). The improvement of the traveling wave velocity calculation method further improves the positioning accuracy. Compared with the traditional positioning method, the average positioning error of this method is reduced by 30%.This method overcomes the shortcomings of the traditional method in poor fault location of wind farm transmission lines. In addition, it is more accurate than the traditional fixed wave velocity method in the calculation of the traveling wave velocity. It can calculate the wave velocity in real time according to the scene and solve the traveling wave velocity can’t be updated with the environment and real-time update. The method is verified in PSCAD/EMTDC.
An Algorithm Based on Fuzzy Inner Product for the Recognition of Dry Vegetal Mass in Red-Green-Blue Images
In this paper, a new algorithm seeking to apply the fuzzy inner product for the recognition of vegetal mass in aerospace images acquired by unmanned aircraft vehicles is presented. Two sets of images are utilized, one for dry vegetal mass and another for green vegetal mass, with this work we pretend to automatically detect droughts, deforestation, damage due to fires and thus to obtain an early alert system for wildfires. We make an introduction to fuzzy systems, inner product and the union of both for applying to histograms and red-green-blue (RGB) image matrices, finding the points of interest necessary to obtain a certain level of dry vegetal mass in the RGB image of study.
Comparative Study of Linear Oscillating Generators for Hybrid Electric Vehicle
This paper presents the comparative study of linear oscillating generators for hybrid electric vehicle application. The focus of the study is the suggestion of the optimal model through the comparison of each topology. First of all, there are four topologies of the proposed to this study on the basis of the existing literature; Cartesian topology, cylindrical topology, cylindrical reluctance machine, and transverse flux machine. All topology is achieved using equivalent magnetic circuit considering leakage elements as initial modeling. First, the proposed topology is Cartesian topology with ironless translator. It is investigated by number of phases and number of pole pairs. In addition, the optimal process is performed by parameter studies of the design variables under the constraints. Second, cylindrical topology with back-iron translator is described by number of phases and displacement of stroke. Thirdly, reluctance machine with cylindrical topology is studied. The shape of mover teeth in geometric aspect is used as the method for the force ripple minimization and increasing magnetic flux. Finally, transverse flux machine is considered by dividing the transverse flux electric excited type and the transverse flux permanent magnet excited type. Additionally, three-dimensional analysis in this machine is accomplished due to the asymmetric structure with another three axes. Among the four proposed topologies, the optimal topology is selected as cylindrical topology with the back-iron translator of single-phase system by characteristics of each topology. For more accurate analysis of an oscillating machine, it will be compared by moving just one-pole pitch forward and backward the thrust of single-phase system and three-phase system. Finally, the detailed design of the optimal topology takes the magnetic saturation effects into account by finite element analysis. Besides, the losses are examined to obtain more accurate results; copper loss in the conductors of machine windings, eddy-current loss of permanent magnet, and iron-loss of specific material of electrical steel. The considerations of thermal performances and mechanical robustness are essential, because they have an effect on the entire efficiency and the insulations of the machine due to the losses of the high temperature generated in each regions of the generator. Besides electric machine with linear oscillating movement requires a support system that can resist dynamic forces and mechanical masses. As a result, the fatigue analysis of shaft is achieved by the kinetic equations. Also, the thermal characteristics are analyzed by the operating frequency in each region. The results of this study will give a very important design rules in the design of linear oscillating machines. It enables us to more accurate machine design and more accurate prediction of machine performances.
A Transform Domain Function Controlled Variable-Step-Size Least Mean Square Algorithm for Sparse System Identification
The convergence rate of the least-mean-square (LMS) algorithm deteriorates if the input signal to the filter is correlated. In a system identification problem, this convergence rate can be improved if the signal is white and/or if the system is sparse. We recently proposed a sparse transform domain LMS-type algorithm that uses a variable step-size for a sparse system identification. The proposed algorithm provided high performance even if the input signal is highly correlated. In this work, we investigate the performance of the proposed TDLMS algorithm for a large number of filter tap which is also a critical issue for standard LMS algorithm. Additionally, the optimum value of the most important parameter is calculated for all experiments. Moreover, the convergence analysis of the proposed algorithm is provided. The performance of the proposed algorithm has been compared to different algorithms in a sparse system identification setting of different sparsity levels and a different number of filter taps. Simulations have shown that the proposed algorithm has prominent performance compared to the other algorithms.
A Quasi-Z-Source Based Full Bridge Isolated Dc-Dc Converter as a Power Module for Pv System Connected to HVDC Grid
Grid connected photovoltaic (PV) power system is to be developed in the direction of large-scale, clustering. Large-scale PV generation systems connected to HVDC grid have many advantages compared to its counterpart of AC grid, and DC connection is the tendency. DC/DC converter as the most important device in the system, has become one of the hot spots recently. The paper proposes a Quasi Z-Source(QZS) based Boost Full Bridge Isolated DC/DC Converter(BFBIC) topology as a basis power module and combination through input parallel output series(IPOS) method to improve power capacity and output voltage to match with the HVDC grid. The topology has both traditional voltage source and current source advantages, it permit the H-bridge short through and open circuit, which adopt utility duty cycle control and achieved input current and output voltage balancing through input current sharing control strategy. A ±10kV/200kW system model is built in MATLAB/SIMULINK to verify the proposed topology and control strategy.
Large-Scale Photovoltaic Generation System Connected to HVDC Grid with Centralized High Voltage and High Power DC/DC Converter
Large-scale photovoltaic (PV) generation system connected to HVDC grid has many advantages compared to its counterpart of AC grid. DC connection can solve many problems that AC connection faces, such as the grid-connection and power transmission, and DC connection is the tendency. DC/DC converter as the most important device in the system has become one of the hot spots recently. The paper proposes a centralized DC/DC converter which uses Boost Full Bridge Isolated DC/DC Converter(BFBIC) topology and combination through input parallel output series(IPOS) method to improve power capacity and output voltage to match with the HVDC grid voltage. Meanwhile, it adopts input current sharing control strategy to realize input current and output voltage balance. A ±30kV/1MW system is modeled in MATLAB/SIMULINK, and a downscaled ±10kV/200kW DC/DC converter platform is built to verify the proposed topology and control strategy.
Effects of LED Lighting on Visual Comfort with Respect to the Reading Task
Lighting systems in interior architecture need to be designed according to the function of the space, the type of task within the space, user comfort and needs. Desired and comfortable lighting levels increase task efficiency. When natural lighting is inadequate in a space, artificial lighting is additionally used to support the level of light. With the technological developments, the characteristics of light are being researched comprehensively, and several business segments have focused on its qualitative and quantitative characteristics. These studies have increased awareness and usage of artificial lighting systems, and researchers have investigated the effects of lighting on physical and psychological aspects of human in various ways. The aim of this study is to research the effects of illuminance levels of LED lighting on user visual comfort. Eighty participants from the Department of Interior Architecture of Çankaya University participated in three lighting scenarios consisting of 200 lux, 500 lux and 800 lux that are created with LED lighting. Each lighting scenario is evaluated according to six visual comfort criteria in which a reading task is performed. The results of the study indicated that LED lighting with three different illuminance levels affects visual comfort in different ways. The results are limited to the participants and questions that are attended and used in this study.
Perspectives of Renewable Energy in 21st Century in India: Statistics and Estimation
With the favorable geographical conditions of Indian-subcontinent, the subcontinent is suitable for flourishing renewable energy. Increasing amount of dependence on coal and other conventional sources is driving the world into pollution and depletion of resources. This paper presents with the statistics of energy consumption and energy generation in Indian Sub-continent, which notifies us with the increasing energy demands surpassing energy generation. Since major portion of the power produced in India is from thermal plants, the more the demand for energy the more is the usage of thermal plants which in turn causes depletion of reserves and emissions in the atmosphere causing global warming. Renewable energy sources in India is then analyzed and seen that world today looks towards India for its promising growth in renewable energy that happens to be totally new in this technical field.
Disaster Education and Children with Visual Impairment
This study describes a series of learning workshops, which took place within CUIDAR project. The workshops aimed to empower children to share their experiences and views in relation to natural hazards and disasters. The participants in the workshops were ten primary school students who had severe visual impairments or multiple disabilities and visual impairments (MDVI). The main objectives of the workshops were: a) to promote access of the children through the use of appropriate educational material such as texts in braille, enlarged text, tactile maps and the implementation of differentiated instruction, b) to make children aware regarding their rights to have access to information and to participate in planning and decision-making especially in relation to disaster education programs, and c) to encourage children to have an active role during the workshops through child-led and experiential learning activities. The children expressed their views regarding the meaning of hazards and disasters. Following, they discussed their experiences and emotions regarding natural hazards and disasters, and they chose to place the emphasis on a hazard, which was more pertinent to them, their community and their region, namely fires. Therefore, they recalled fires that have caused major disasters, and they discussed about the impact that these fires had on their community or on their country. Furthermore, they were encouraged to become aware regarding their own role and responsibility to prevent a fire or get prepared and know how to behave if a fire occurs. They realized that prevention and preparation are a matter of personal responsibility. They also felt the responsibility to inform their own families. Finally, they met important people involved in fire protection such as rescuers and firefighters and had the opportunity to carry dialogues. In conclusion, through child led workshops, experiential and accessible activities, the students had the opportunity to share their own experiences, to express their views and their questions, to broaden their knowledge and to realize their personal responsibility in disaster risk reduction, specifically in relation to fires.
Studies on Radio Frequency Sputtered Copper Zin Tin Sulphide Absorber Layers for Thin Film Solar Cells
Copper Zin tin sulphide (Cu2ZnSnS4 or CZTS) is found to be better alternative to Copper Indium gallium diselenide as absorber layers in thin film based solar cells due to the utilisation of earth-abundant materials in the midst of lower toxicity. In the present study, Cu2ZnSnS4 thin films were prepared on soda lime glass using (CuS, ZnS, SnS) targets and were deposited by three different stacking orders, using RF Magnetron sputtering. The substrate temperature was fixed at 300 °C during the depositions. CZTS thin films were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and UV-Vis-NIR spectroscopy. All the samples exhibited X-ray peaks pertaining to (112) kesterite phase of CZTS, along with the presence of a predominant wurtzite CZTS phase. X-ray photoelectron spectroscopy revealed the presence of all the elements in all the samples. The change in stacking order clearly shows that it affects the structural and phase properties of the films. Relative atomic concentrations of Zn, Cu, Sn and S, which are determined by high-resolution XPS core level spectra integrated peak areas revealed that the CZTS films exhibit inhomogeneity in both stoichiometry and elemental composition. Raman spectroscopy studies on the film showed the presence of CZTS phase. The energy band gap of the CZTS thin films was found to be in the range of 1.5 eV to 1.6 eV. The films were then annealed at 450 °C for 5 hrs and it was found that the predominant nature of the X-ray peaks has transformed from Wurtzite to Kesterite phase which is highly desirable for absorber layers in thin film solar cells. The optimized CZTS layer was used as an absorber layer in thin film solar cells. ZnS and CdS were used as buffer layers which in turn prepared by Hot wall epitaxy technique. Gallium doped Zinc oxide was used as a transparent conducting oxide. The solar cell structure Glass/Mo/CZTS/CdS or ZnS/GZO has been fabricated, and solar cell parameters were measured.