WSEAS CONFERENCES. WSEAS, Unifying the Science

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Volume 10, 2011
ISSN: 1109-2734
E-ISSN: 2224-266X








Issue 1, Volume 10, January 2011

Title of the Paper:  New General Transformations for 2-D FIR and IIR Filters’ Design


Authors: Nikos E. Mastorakis

Abstract: In this paper, new general transformations for designing 2-D (Two-Dimensional) FIR and IIR filters are provided. The present methodology can be viewed as an extension of the McClellan Transformations and can be applied in several cases of 2-D FIR and IIR filter design. Numerical examples illustrate the validity and the efficiency of the method.

Keywords: 2-D Filters, FIR Filters, IIR Filters, Multidimensional Systems, Multidimensional Filters, Filter Design, McClellan Transformations

Title of the Paper:  Transformations for Direct Design of 2-D Filters from Appropriate 1-D Functions


Authors: Nikos E. Mastorakis

Abstract: In this paper, general transformations for designing 2-D (Two-Dimensional) IIR filters are provided. The present approach can be viewed as an extension of the classical method of magnitude approximation and can be applied in several cases of 2-D filter design. Numerical examples illustrate the validity and the efficiency of the method.

Keywords: 2-D Filters, FIR Filters, IIR Filters, Multidimensional Systems, Multidimensional Filters, Filter Design, McClellan Transformations

Title of the Paper:  Nonlinear Integrator Backstepping for Traffic Flow Speed Control of Automated Freeway System


Authors: Xu-Hua Yang, Sheng-Yong Chen, Wan-Liang Wang

Abstract: In an automated freeway system environment, computers replace artificial driving and control vehicles accompany movement, which can greatly reduce randomness. In this paper, we propose a traffic flow speed controller with lower complexity which can send speed commands to regulate the speeds of vehicles in each section of a freeway. On the basis of the theory of nonlinear integrator backstepping, the controller can guarantee exponential convergence of the traffic flow speed at each section to the desired speed. Compared with former method, the establishment of this controller need not solve inverse matrix, and therefore, reduces algorithm’s complexity, improves the algorithm efficiency and automatically satisfies the controllability condition. Simulations show that this controller can effectively reduce congestion and helps to achieve a smooth traffic flow on a congested freeway.

Keywords: Speed controller, automated freeway system, traffic control, nonlinear integrator backstepping, traffic flow model, exponential convergence

Title of the Paper:  An Evaluation for the design of Asynchronous Systems


Authors: Sun-Yen Tan, Wen-Tzeng Huang

Abstract: The asynchronous circuit style is based on micropipelines, a style used to develop asynchronous microprocessors at Manchester University. This paper has presented some engineering work on developing a technique of sharing resources for micropipeline circuits. The work presented in this paper shows a comparison of 2-phase and 4-phase implementations in transistor count, speed, and energy. Though the nature of the work is mainly engineering, there are some significant new insights gained in the course of the work. In resource sharing the 2-phase implementations have better performance than the four-phase implementations. There is no “return to zero” problem. Fork and join cost nothing to the two-phase implementations. With some additional buffer stages the 4-phase implementations using the fully decoupled and long hold latch control circuits can also implement resource sharing. However, the four-phase implementations using the simple and semi-decoupled latch control circuits require more buffer stages to avoid deadlock.

Keywords: Asynchronous design, Micropipelines, Processor, Sharing resources, Synthesis

Issue 2, Volume 10, February 2011

Title of the Paper:  Design, Implementation and Evaluation of an Optimal Iterative Learning Control Algorithm


Authors: V. Vita, A. Vitas, G. E. Chatzarakis

Abstract: Iterative learning control (ILC) is used to control systems that operate in a repetitive mode, improving tracking accuracy of the control by transferring data from one repetition of a task, to the next. In this paper an optimal iterative learning algorithm for discrete linear systems is designed and implemented. The design and implementation that have been done using Matlab® 7 and Simulink are described in detail. The algorithm is applied on several representative discrete systems cases in order to be evaluated and to reveal its capabilities and limitations.

Keywords: Discrete linear systems; iterative learning control; Matlab® 7; simulation

Title of the Paper:  Application of Neural Networks for Control of Inverted Pendulum


Authors: Valeri Mladenov

Abstract: The balancing of an inverted pendulum by moving a cart along a horizontal track is a classic problem in the area of automatic control. In this paper two Neural Network controllers to swing a pendulum attached to a cart from an initial downwards position to an upright position and maintain that state are described. Both controllers are able to learn the demonstrated behavior which was swinging up and balancing the inverted pendulum in the upright position starting from different initial angles.

Keywords: Neural networks, inverted pendulum, nonlinear control, neural network controller

Title of the Paper:  Identification of Impending Interturn Faults in Random Wound Induction Motors Used in Adjustable Speed Drives


Authors: S. Ponnuswamy Rajkumar, J. Sudesh Johny, A. Ebenezer Jeyakumar

Abstract: Diagnosis of stator current has been presented by several authors for identifying various bearing and rotor faults in an induction motor. However, there is very limited literature covering the effect of interturn faults on the stator current pattern. This is due to the reason that the effect of motor interturn insulation faults in the initial stages being not discernable and any changes in the capacitive current components are negligibly very small and of very high frequency content. This paper deals with a simple technique, utilizing the effect of the interturn fault in modifying the high frequency components of the applied pulse width modulated (PWM) voltage. Insulation Resistance (IR) and Polarization Index (PI) are two universally accepted diagnostic tests for insulation tests. The change in insulation strength between the turns affects the capacitive component of the stator line current. Resulting changes in wave shapes of applied voltage have been studied with respect to both the distance of interturn faults from line end and reduction in the insulation strength; and hence in the insulation resistance value. The studies have been made by computer simulation and validated by experiments. There is ample evidence that an impending and progressing interturn fault can be identified in Adjustable Speed Drives driven by frequency converters by studying line end coil voltage waveforms.

Keywords: Repetitive switching surges, Stator line current, PWM Voltage, Adjustable speed drives, Motor insulation, Interturn faults, High-frequency capacitive current components

Title of the Paper:  Unbalanced-Grid-Fault Ride-Through Control for a Doubly Fed Induction Generator Wind Turbine with Series Grid-Side Converter


Authors: Yong Liao, Hui Li, Jun Yao

Abstract: The grid codes now require doubly fed induction generator (DFIG) wind turbines having the “low voltage ride-through (LVRT)” capability. However, a traditional DFIG with a partially rated back-to-back converter has inherent difficulties to ride through the grid faults, especially for the unbalanced grid faults. Modifications to the traditional DFIG configuration for ride-through have become necessary. A DFIG system with series grid-side converter (SGSC) has an excellent potential for voltage dips tolerance. This paper analyzes the reasons of a DFIG system with SGSC for ride-through and presents a control scheme for operation under unbalanced grid faults conditions. During grid faults, the each component of the generator’s stator flux is effectively controlled through the SGSC. Also, the stator and rotor currents are further restricted by controlling the rotor-side converter (RSC) to reduce the absorbing energy from wind turbine. Then, successful ride-through of a DFIG system with SGSC under all types of severe unbalanced grid faults at the point of common coupling (PCC) are achieved with reduced electromagnetic torque oscillation. The proposed control scheme is validated by means of simulations.

Keywords: Doubly fed induction generator (DFIG), series grid-side Converter (SGSC), unbalanced grid fault, wind turbine, low voltage ride-through (LVRT), wind power generation, voltage dips, voltage sags

Issue 3, Volume 10, March 2011

Title of the Paper:  An Analyze on a Wood Processing Automatic Machine


Authors: Gabriel Nicolae Popa, Corina Maria Dinis, Sorin Ioan Deaconu, Angela Iagar

Abstract: In this work is presenting an automatic machine used in the wood processing industry. These machines have the advantage of flexibility in achieving of some diverse finished products, by using the same processing tools, the single modification being made on the machine’s program. As accurate drive elements are also used stepping motors that can be supplied and controlled in different modes. Hereby is presenting a unipolar control mode of a 4-coil stepping motor controlled by 4 transistors with field effect. For this circuit, there is the possibility of its control by the development mode with microcontroller or PC.

Keywords: Automatic machine, control, stepping motor, unipolar

Title of the Paper:  Interleaved Soft-Switching Buck Converter with Coupled Inductors


Authors: Cheng-Tao Tsai, Chih-Lung Shen

Abstract: This paper presents an interleaved soft-switching buck converter with coupled inductors to extend duty ratio for high step-down voltage applications. In the proposed converter, a single-capacitor turn-off snubber is introduced to limit voltage rising rate of active switches to reduce turn-off loss. To handle the energy trapped in the leakage inductance of the coupled inductors, simple passive-clamp circuits are added to the proposed converter, which can effectively recycle the energy and suppress voltage spike. To highlight the merits of the proposed converter, its performance indexes, such as voltage gain function and component stresses, are analyzed and compared with those of the conventional interleaved buck converter. In this study, a prototype of the proposed converter, of which input voltage range is 127-177 Vdc, output voltage is 12 Vdc, and power capacity rates at 240 W, has been designed and implemented to verify the feasibility. From experimental results, it has been shown that conversion efficiency up to 85% can be achieved at full load condition.

Keywords: Interleaved, soft-switching, coupled inductors, leakage inductance, passive-clamp circuits

Title of the Paper:  A Transfer Method of Public Transport Network Based on Adjacency Matrix Multiplication Searching Algorithm


Authors: Bo Wang, Xu-Hua Yang

Abstract: In this paper, we model the public transport network (PTN) to an unweighted network by space L and space P method. The adjacency matrix is used to express this network, in which 1 denotes connection between two vertices and 0 denotes disconnection. According to the complex theory, the statistical characteristics (including average clustering coefficient, average shortest path length, and so on) of the real PTN of Hangzhou are analyzed. By the shortest path algorithm of matrix multiplication, all the least transfer routes between any two bus stations of Hangzhou are gotten. Then the PTN of Hangzhou is modeled to a weighted network using the straight-line distances between the bus stations which are computed by every station’s longitudes and latitudes as the weights. To compare the weights (namely the straight-line distances) of all the least transfer routes, the transfer routes between any two bus stations which not only have the least transfer times but also the shortest straight-line distances are obtained. Finally, by some practical bus stations of Hangzhou, this transfer method is validated.

Keywords: Public transport network; Small-world; Weighted network; Transfer route; Matrix multiplication

Issue 4, Volume 10, April 2011

Title of the Paper:  Robots Implementation for Odor Source Localization Using PSO Algorithm


Authors: Jatmiko W, Jovan F, Dhiemas R.Y.S, T. Fukuda, K. Sekiyama

Abstract: Research topics in robotic application is quite varies but one of the most interesting topic is odor source localization. This research combine the robot ability to recognize odor and track the movement so that robotcan find the source. Most of the research are done to improve the algorithm to localize the source by using simulation software. This paper tries to verify the robustness of one of the localization method known as Particle Swarm Optimization (PSO) in the real-world implementation. This paper will shows robot model that used in the experiment and also discuss the architecture to implement robot behavior. A group of mobile robots equipped with wireless communication device and odor sensors is employed. The experiment is conduct in area of 488cm x 488cm with dynamic odor source in one end. The experiment also used a set of camera to track robots position. The experiement result verifies that PSO is technically sound for real-world odor source localization. In this experiment, PSO can localized the source in 360 seconds or bellow.

Keywords: PSO, Al-Fath, Odor Source

Title of the Paper:  A Doubly-Excited DC- to- 3-Phase AC Buck-Boost Converter Gives Sinusoidal Waveforms: Design, Simulation & Control


Authors: M. Ezzat

Abstract: This paper presents a new topology for converting a DC voltage to a 3-phase AC one. The proposed converter is excited from two separate DC supplies so the term "Doubly-Excited". The most important features of the proposed converter are the output voltage (AC Voltage) is lower or higher than the input one (DC Voltage), controllable voltage and frequency, and the output voltage and current are approximately sinusoidal which means low harmonics content. Also, the paper presents the simulation of the proposed converter in different modes of operation under control to show the effectiveness of the proposed control strategy.

Keywords: Boost, Control, DC- to -3-phase AC Converter, Design, Simulation

Title of the Paper:  An Enhanced Load Transfer Scheme for Power Distribution Systems Connected with Distributed Generation Sources


Authors: Wen-Chih Yang, Wei-Tzer Huang

Abstract: This paper presents an enhanced load transfer scheme for power distribution systems connected with distributed generation sources. Load transfer is an important approach to improve the reliability of power distribution systems. The proposed load transfer scheme takes into account the effects of distributed generation sources on power distribution systems. Hence, it is more useful than conventional load transfer scheme. In this paper, the procedures of conventional and proposed load transfer scheme are addressed in detail. Two example systems for computer simulation were constructed and several simulation scenarios were carried out by this work. Simulation results shown in this paper clearly indicate the troubles of conventional load transfer scheme and the practicability of the proposed load transfer scheme.

Keywords: Load transfer, Distribution system, Distribution feeder, Distributed generation source, Interconnection

Issue 5, Volume 10, May 2011

Title of the Paper:  A Preventive Control Model for Static Voltage Stability and Thermal Stability based on Power Transfer Capabilities of Weak Branches


Authors: Wei Yan, Xiuqiong Hu, Juan Yu, Wenyuan Li

Abstract: A preventive control model for static voltage stability and thermal stability is presented using the apparent power constraints on weak branches as both static voltage stability constraints and thermal stability constraints. Firstly, a localized line-based voltage stability index is selected to determine the weak branches as well as their power transfer capabilities and the critical contingencies. A static security analysis method, which is based on PQ decouple method, is adopted to obtain the quadratic apparent power expressions of weak branches following each critical contingency. Then, the apparent power constraints on weak branches are established combining the power transfer capabilities and the apparent power expressions of weak branches. The proposed preventive control model has a quadratic form and can be solved by the predictor-corrector primal dual interior method. The simulation results for three IEEE test systems demonstrate the correctness and effectiveness of the proposed preventive control model.

Keywords: Preventive control, Static voltage stability, Thermal stability, Weak branch, Apparent power constraint, Quadratic optimal model

Title of the Paper:  About the Definition of Parameters and Regimes of Active Two-Port Networks with Variable Loads on the Basis of Projective Geometry


Authors: Penin Alexandr

Abstract: Disadvantages of some well- known methods of analysis of electric circuits with variable loads are analyzed. To interpret a mutual influence of the loads, some methods of the projective geometry are used. The application of the projective coordinates allows receiving the equation of the active two-port network in a normalized or relative form as well as defining the scales for the currents and conductivity of the loads. Such approach makes it possible to estimate the qualitative characteristics of the current regimes, to compare the regime efficiency of the different circuits. The formulas of the recalculation of the currents, which possess the group properties at change of conductivity of the loads, are obtained. It allows expressing the final values of the currents through the intermediate changes of the currents and conductivities. The generalized equivalent generator of the active two-port network in the form of the passive two-port network and a set of the sources of a current and voltage is proposed. The parameters of these sources do not depend on certain conductivities of the passive two-port network.

Keywords: Thevenin’s theorem, load characteristics, projective geometry, two-port networks

Title of the Paper:  SVC Implementation Using Neural Networks for an AC Electrical Railway


Authors: Saeid Veysi Raygani, Bijan Moaveni, Seyed Saeed Fazel, Amir Tahavorgar

Abstract: This paper presents an on-line method for implementation of a static var compensator (SVC) in a real ac autotransformer (AT)-fed electrical railway for reactive power compensation using Neural Networks (NN). Genetic algorithm (GA) can be the off-line minimizing function for reactive power compensation. Consequently, the nonlinear auto-regressive model with exogenous Inputs networks in series-parallel arrangement (NARXSP) is implemented as a predictor and methodology in order to diminish calculation time and making this method practicable. To study load flow and reactive power compensation for this unique system, forward/backward sweep (FBS) load flow method is applied. MATLAB software is used for programming and simulations.

Keywords: Neural network (NN), reactive power compensation, static var compensator (SVC), genetic algorithm (GA), AC electrical railways load flow, forward/backward sweep (FBS)

Issue 6, Volume 10, June 2011

Title of the Paper:  Investigation Life Time Model of 22 kV XLPE Cable for Distribution System Applications in Thailand


Authors: Boonruang Marungsri, Anucha Rawangpai, Nimit Chomnawang

Abstract: Cross-linked polyethylene (XLPE) high voltage cables have been widely used in power transmission and distribution systems. Ageing deterioration of XLPE insulating material can not be avoided because it is made of polymeric material. This paper present results of artificial ageing test of 22 kV XLPE cable for a distribution system application in Thailand. XLPE insulating material of 22 kV cable was sliced to 60-70 ěm in thick and subjected to AC high voltage stress at 23?C, 60?C, 75?C and 90?C. The specimens were tested under different electrical stress levels varying from 50kV/mm to 130kV/mm. Testing voltage was constantly applied to the specimen until breakdown. Five specimens were tested at each temperature and voltage stress level. Breakdown voltage and average time to breakdown were used to evaluate life time of insulating material. Furthermore, the physical model by J. P. Crine for prediction life time of XLPE insulating material was adopted as life time model and was determined in order to compare with the experimental results. In addition, Fourier transform infrared spectroscopy (FTIR) for chemical analysis and scanning electron microscope (SEM) for physical analysis were conducted on the tested specimens.

Keywords: Artificial accelerated ageing test, XLPE cable, distribution system, insulating material, life time, life time model

Title of the Paper:  Development of an Advanced Embedded System for Description of Electrophysiological Phenomena in Ornamental Plants by Biosignals Processing


Authors: Kalovrektis K., Ganetsos Th., Shammas N. Y. A., Taylor I., Lykas Ch., Andonopoulos I., Lekakis I.

Abstract: Extracellular electrical signals that are produced from plants have different patterns depending on factors that may cause stress such as water deficiency, nutrient shortages, high salinity level in the root environment etc. In practice, growers and greenhouse control systems acts against the stress factor when visible symptoms are observed, or when the measured values of parameters related to the stress are outside certain limits during a pre-defined period. However, the decrease in plant growth has already begun during this period with consequences for production. The objective of this work is the development of an advanced embedded wireless sensor to detect electrophysiological phenomena in order to investigate the correlation of biosignal patterns to salinity stress in ornamental plants. This embedded system could be used to improve the efficiency of irrigation control systems especially in soilless cultures. For this reason an integrated embedded hardware was designed for plant biosignal measurements. In order to avoid white Gaussian noise (WGN caused from 50 Hz power line noise as well as the noise of the electrical devices operating inside the greenhouse), the IEEE 802.15.4 protocol was used for wireless communication to the embedded systems. Electrical potential difference in leaves of single stem Chrysanthemum (Chrysanthemum moriflorum) plants grown in soilless culture and irrigated with low and high electrical conductivity (EC) nutrient solution were measured using the embedded wireless system and a traditional wire data acquisition system (DAQ). The measurements are recorded for a period of 4 days, via a data acquisition system and processed using LabVIEW code. The results show that biosignal measurements on plants, obtained with the use of the design wireless embedded system have a negligible error in contrast to wired data acquisition, since these are not affected by RF and other similar signal noise. The experimental measurements showed that there is a significant correlation between the mean voltage value of the measured biosignal ( )and the EC level of the substrate where the plants were grown.

Keywords: Biosignal, chrysanthemum, Ag/AgCl, wireless sensor, amplifier, salinity stress, electrical conductivity

Title of the Paper:  Possible Solution of Decoupling and Invariance of Multi-variable Control Loop by Using Binding and Correction Members


Authors: Pavel Navratil, Libor Pekar

Abstract: The paper describes one of possible methods how to control of multi-variable control loops. In this case the used method of control uses the so called main controllers, binding members and correction members. This control method combines classical approach for ensuring decoupling of multi-variable control loop by means of binding members and the use of the correction members for ensuring invariance of multi-variable control loop by means of two approaches. Main controllers can be proposed by arbitrary single-variable synthesis method. Simulation verification of the used control method is carried out for example of three-variable loop of a steam turbine.

Keywords: Decoupling of control loop, control, invariance of control loop, simulation

Issue 7, Volume 10, July 2011

Title of the Paper:  A Robust Asynchronous Early Output Full Adder


Authors: Padmanabhan Balasubramanian

Abstract: A robust asynchronous full adder design corresponding to early output logic, synthesized using the elements of a standard cell library is presented in this paper. As the name suggests, the adder ensures gate orphan freedom and neatly fits into the self-timed system architecture. In comparison with many of the indicating full adder designs, which can be embedded in the self-timed system, it is found that the proposed full adder enables reduction in latency by 20.7%, occupies lesser area by 15.4% and features minimized average power dissipation by 8.6% against the best design metrics of its counterparts. These design estimates correspond to simulation results of the 32-bit carry-ripple adder circuit; derived by targeting a high-speed 130nm bulk CMOS process technology. Also, the proposed full adder facilitates a faster reset and the return-to-zero for the fundamental carry-propagate topology is achieved with only two full adder delays.

Keywords: Full adder, Asynchronous design, Early propagation, Indication, Standard cells, CMOS process

Title of the Paper:  An Efficient EPI and Energy Consumption of 32 bit ALU Using Shannon Theorem Based Adder Approach


Authors: C. Senthilpari, G. Ramanamurthy, P. Velrajkumar

Abstract: This paper proposed two full adder circuits such as mixed Shannon and Shannon theorem based adder circuits. The mixed adder circuit developed by using MCIT for the sum operation and Shannon technique for carry and other one designed completely by using Shannon theorem. The ALU circuit consists of AND, OR, multiplexer and adder circuits that are designed by using proposed Shannon theorem. The 32-bit ALU circuits are analyses by BSIM 4 parameter analyzer. The power dissipation of total circuit, propagation delay and area are analyzed for 32 bit ALU. The binvert Shannon adder based ALU circuit gives better performance in terms of power dissipation, propagation delay, and throughput than bit-sliceALU circuit.

Keywords: ALU, MCIT, Shannon theorem, CPL, Power Dissipation, Throughput

Title of the Paper:  Comparison of Lyapunov Function for Different Strategies of Optimization of Analogue Networks using Parallel Computing


Authors: Alexander Zemliak, Antonio Michua

Abstract: The problem of designing of analog network for a minimal computer time has been formulated as the functional minimization problem of the control theory. The design process in this case is formulated as the controllable dynamic system. The optimal sequence of the control vector switch points was determined as a principal characteristic of the minimal-time system design algorithm. The conception of the Lyapunov function was proposed to analyze the behavior of the process of designing. The special function that is a combination of the Lyapunov function and its time derivative was proposed to predict the design time of any strategy by means of the analysis of initial time interval of the process of network optimization. The parallel computing serves to compare the different strategies of optimization in real time and to select the best strategy that has the minimal computer time. This approach gives us the possibility to select the quasi optimal strategy of network optimization by analyzing the initial part of the total design process only.

Keywords: Minimal-time system designing, control theory application, network optimization, Lyapunov function, parallel computing

Issue 8, Volume 10, August 2011

Title of the Paper:  On Brayton-Moser Network Decomposition and State-Space Energy based Generalization Of Nose-Hoover Dynamics


Authors: Josef Hrusak, Milan Stork, Daniel Mayer

Abstract: This paper deals with generalization of the Brayton-Moser network decomposition and related structural properties to a relatively large class of finite dimensional strictly causal systems, which can be described in the state-space representation form. The resulting energy-metric function is defined for dissipative systems and is induced by the output signal dissipation power. It is demonstrated that such a power-oriented approach determines both, the structure of a system representation as well as the corresponding system state space topology. A special form of physically correct internal structure of an equivalent state space representation has been derived as a natural consequence of strict causality, the state-space energy conservation, dissipativity assumption and the state minimality requirement.

Keywords: State-space energy, decomposition, dissipation power, active power, reactive power

Title of the Paper:  Full-Graph Solution of Switched Capacitors Circuits by Means of Two-Graphs


Authors: Bohumil Brtnik

Abstract: Circuits with switched capacitors are described by a capacitance matrix. As there are also graph methods of circuit analysis in addition to algebraic methods, it is clearly possible in theory to carry out an analysis of the whole switched circuit in two-phase switching exclusively by the graph method as well. The phase of switching are called even (E) and odd (O), not 1 and 2 to avoid confusion between the sign of the phases and of the nodes. For this purpose it is possible to plot a Mason graph of a circuit, use two graphs to reduce oriented graphs for all the four phases of switching, and then plot a summary MC-graph from charge and voltage graphs. Summary MC-graph is now constructed by the incomplete common skeletons of the V-graph and the Q-graph in all four phases, branches obtained for EO and OE phase are drawn between these nodes, while their resulting transfer is multiplied by 2 1 -z to express the delay between the two phases. This summary MC-graph can then be interpreted by the Mason’s relation to provide transparent voltage transfers, and so it is possible to reach the final result a quite fully graphically. This method can be used for circuits containing operational amplifier with the break point frequency, too, but summa graph is rather complicated in this case, because this description is based on the modified nodal method, where the number of nodes is remains.

Keywords: Switched capacitors, two-graphs, Mason-Coates graph, summa graph, Mason/s rule, break point frequency

Title of the Paper:  ASIC Implementation of High Speed Processor for Calculating Discrete Fourier Transformation using Circular Convolution Technique


Authors: P. Saha, A. Banerjee, A. Dandapat, P. Bhattacharyya

Abstract: The improvement in speed and power for calculating discrete Fourier transformation using circular convolution is well established, but all the work so far been reported are at FPGA (gate) level. In this paper ASIC implementation of high speed processor for calculating Discrete Fourier Transformation (DFT) based on circular convolution architectures is reported for the first time. The IEEE-754 single precision format was considered for the representation of the twiddle factors. The improvement of the speed for floating point multiplication/addition was achieved by canonical sign digit implementation methodology, which reduced the stages of operation significantly. The functionality of these circuits was checked and performance parameters such as propagation delay, dynamic switching power consumptions were calculated by spice spectre using standard 90nm CMOS technology. The implementation methodology ensure substantial reduction of propagation delay in comparison with systolic array and memory based implementation, most commonly used architectures, reported so far, for DFT processors. The propagation delay of the resulting 16 point DFT processor is only 23.79µs while the power consumption of the same was 14.32mW only for a layout area of ~12mm2. Almost 50% improvement in speed from earlier reported DFT processors, e.g. systolic array and memory based implementation methodology, has been achieved.

Keywords: DFT, FFT, Circular convolution, Multiply and accumulate (MAC), Canonical sign digit (CSD) adder, CSD Multiplier

Issue 9, Volume 10, September 2011

Title of the Paper:  A New CMOS Current Controlled Oscillator with Minimum Phase Noise Based on a Low Parasitic Resistance CCII


Authors: Samir Ben Salem, Achwek Ben Saied, Dorra Sellami Masmoudi, Mourad Loulou

Abstract: In this paper we present a design of a minimum phase noise current controlled oscillator in CMOS technology. Owing to their high degree of controllability, the second generation current conveyer is used as a basic block for our oscillator. Thus, the first step in our design was to improve static and dynamic behaviour of second generation current conveyers. We present therefore a design of CMOS class AB second generation current conveyors. The translinear implementation in CMOS technology was first studied and then a considerable improvement of the parasitic series resistance on port X is done by presenting a structure of CCII. With a control current of 300 ěA, a reduction of RX by a factor of 10 is observed leading to a notable improvement of the frequency behaviour. This improved CCII version was used as a basic building block in the design of a new current controlled oscillator covering [100MHz-600MHz] frequency is presented. Phase noise characteristics of the presented oscillator are investigated. We present then a new methodology of modelling and optimisation of phase noise of current controlled oscillators for CMOS process. This optimization strategy leads to a minimum phase noise acting on device geometries and design sources. PSpice simulation results are performed using CMOS 0.35 ěm process of AMS.

Keywords: Current Controlled Oscillators, Standard CMOS current conveyor, CCII, cascode structure, Conveyor characterization, RF application, Phase noise optimisation

Title of the Paper:  Investigation of Some Quite Interesting Divisibility Situations in a Signature Analyzer Implementation


Authors: Afaq Ahmad

Abstract: When designing error detecting and correcting systems, cryptographic apparatus, scramblers and other secure, safe and authenticated communication and digital system response data compression devices, the division of polynomials are frequently involved. Commonly, the process of division is implemented by using hardware known as Linear Feedback Shift Registers (LFSRs). In digital system testing the technique of Built-In Self Test (BIST) uses this LFSR based division process for response data compression and is popularly known as Signature Analyzer (SA). This paper presents a simulation experiment on the effectiveness study of the SA schemes. The finding of the results of the simulation study reveals that in SA implementation; in general the uses of primitive characteristic polynomials are the best. However, the study further investigates that the use of some critical primitive characteristic polynomials may reverse the effectiveness of the SA schemes i.e. lead to observe maximum aliasing errors.

Keywords: Signature Analyzer, Linear Feedback Shift Registers, Built-In Self-Test, VLSI, Aliasing Errors, Characteristic Polynomial, Primitive Polynomials, Polynomial Division, Cyclic Redundancy Check

Title of the Paper:  Simulation and Research on Three-Phase Parallel PFC with Feed-Forward Compensation


Authors: Chen Qian, He Mingzhi, Trillion Q. Zheng

Abstract: In order to enhance the power factor and minimize the complexity of control strategy, the analysis of a novel three-phase parallel power factor correction with feed-forward compensation is presented. According to the working principle of the topology, hysteresis current control strategy has been proposed for the bi-boost crossing converter. The simulation results verify the stability of the system. As a result, the time sequence of the system is so simple that the switches can be easily controlled to achieve stable output voltage, ideal power factor and current harmonic, while only twenty percents of the total power passes through the Boost converter. In order to achieve ideal power factor and low current harmonic, the output power should be constant.

Keywords: Three-phase power factor correction, Feed-forward compensation, Low current harmonic, Hysteresis current control, Bi-boost crossing converter, Constant-power load

Issue 10, Volume 10, October 2011

Special Issue: Fuzzy Systems and Applications
Editors: Nikos E. Mastorakis, Valeri Mladenov

Title of the Paper:  Advanced Modelling of Complex Processes by Fuzzy Networks


Authors: Alexander Gegov, Nedyalko Petrov, Boriana Vatchova, David Sanders

Abstract: This work presents an application of the novel theory of rule based networks for building models of processes characterised by uncertainty, non-linearity, modular structure and internal interactions. The application of the theory is demonstrated for a flotation process in the context of converting a multiple rule based system into an equivalent single rule based system by linguistic composition of the individual rule bases. During the conversion process, the transparency of the multiple rule based system is fully preserved while its accuracy is improved to a level comparable with the accuracy of the single rule based system.

Keywords: Hierarchical model, network model, data simulation, fuzzy logic, fuzzy systems, process model, input/output models, systems evaluation, knowledge base

Title of the Paper:  Hierarchical Clustering in Power System Based on Fuzzy Transitive Closure


Authors: Shu-Chen Wang

Abstract: This paper presents the applications of hierarchical clustering to the generators in a power system. A useful application of fuzzy mathematics is that the correction of clustering results and determination of whether it can obtain correct transitive closure. Thus, the fuzzy transitive closure plays an important role in hierarchical clustering. Based on the fuzzy relation matrix, the hierarchical cluster analysis can be achieved by using firstly computing a transitive closure matrix on which serial á-cut operations are to be performed. A specific feature of the proposed method is that the hierarchical clustering work can be performed in parallel with the algorithm. The proposed method retains the correctness of transitive closure by reducing the computation complexity. Results from applying the method to a power system are demonstrated to show the validity and effectiveness of the proposed method.

Keywords: Hierarchical Clustering, Power System, Fuzzy Transitive Closure, Fuzzy Similarity Relation, á-cut Operation, Complexity

Title of the Paper:  The Optimal Interval Partition and Second-Factor Fuzzy Set Bi on the Impacts of Fuzzy Time Series Forecasting


Authors: Chi-Chen Wang, Yueh-Ju Lin, Yu-Ren Zhang, Hsien-Lun Wong

Abstract: This study uses two sets of Taiwanese data, the export values as the prediction varialbe and its foreign exchange spot rates as the auxiliary variable, to discuss two important issues of forecasting effects in the fuzzy time series analysis by using One- and Two-factor models. The first issue is the relation between the optimum number of partition equal intervals and forecasting error. The second issue is the setting of fuzzy matrix (Bi) in the model to compare its impacts on forecasting error when it is static or dynamic. The above two issues are investigated with the empirical results. First, the optimum number of partition equal intervals is to select 14 intervals for the information to have the smallest forecasting error in all models for one- or two-factor, or different number of window basis selected. However, if partitioning the information into more than 14 equal intervals, the forecasting error can not be reduced but presents a waving pattern. Second, when the information period is longer and if the selecting window basis is two, under any number of partition intervals, the forecasting error is always smaller for the dynamic Bi than for the static one. However, when the information period is shorter and the window basis is two or three, only partitioning into five or eight equal intervals, the forecasting error will also be smaller for the dynamic Bi.

Keywords: Fuzzy tine series, Two-factor model, Interval partition, Fuzzy relationship matrix, Window base, Taiwan exports, MSE

Title of the Paper:  Determination of Crystallizer Service Life on Continuous Steel Casting by Means of the Knowledge System


Authors: Jiri David, Milan Vrozina, Zora Jancikova

Abstract: In this paper there is described the input analysis of the crystallizer service life control problem for creation and exploitation of the software product in order to apply the knowledge systems complemented by the continuous diagnostics that will significantly reduce the human factor involvement in providing the manufacturing equipments inspection, in identification of technical condition and failures of equipments, specification of failures prediction and possibly also in failures elimination through a partial or total automation.

Keywords: Knowledge system, fuzzy systems, prediction, reliability, lifetime, steel industry

Issue 11, Volume 10, November 2011

Title of the Paper:  Study on the New Topology of Power Electronic Transformer


Authors: Zhibing Wang, Kushan Yu, Xiaoxin Zhou

Abstract: This paper presents a mixed topology of Power Electronic Transformer based on Three-Level converter and H-Bridges. It does take into account two conditions, which includes the development of power electronic devices and manufacturing level of high-frequency transformer in the future. First the paper introduced the fundamentals of PET, and then studied on the mathematical model of the new topology in detail. In order to verify the validity of the new topology, the model of Power Electronic Transformer was simulated by MATLAB/PST toolbox, and indicated the inherent problem, which is unbalance of the neutral point voltage. Therefore, the paper proposed control strategies to maintain the balance, and suppress the effect of ripple voltage on common DC bus. Eventually simulations and experimental results validate the feasibility of the new topology and control strategies.

Keywords: Distributed Generations (DGs), Intelligent Universal Transformer (IUT), Power Electronic Transformer (PET), Solid State Transformer (SST), Space Vector Modulation (SVM), Power Factor Correction (PFC), Renewable Energy Source (RES), Smart Grid (SG)

Title of the Paper:  Investigation of Transient Models and Performances for a Doubly Fed Wind Turbine under a Grid Fault


Authors: Mingyu Wang, Bin Zhao, Hui Li, Chao Yang, Renjie Ye, Z. Chen

Abstract: In order to investigate the impacts of the integration of wind farms into utilities network, it is necessary to analyze the transient performances of wind turbine generation systems (WTGS) with the appropriate transient models. According to the grid code requirements for a wind turbine with doubly fed induction generator (DFIG), the assessments of the impact on the electrical transient performances were investigated for the doubly fed wind turbine with different representations of wind turbine drive-train dynamics models, different initial operational conditions and different active crowbar trip time. Firstly, the different mathematical models of the doubly fed wind turbine were presented, including the electromagnetic transient models of DFIG, a one-mass lumped model, a two-mass shaft flexible model of the wind turbine drive train system, and the power decoupling control strategies of the grid-side converter and the rotor-side converter of DFIG. Secondly, the transient performances of the presented doubly fed wind turbine under a grid fault were compared and evaluated with different equivalent models, parameters and initial operational conditions. And thirdly, the effects of the active crowbar on the transient performances of the doubly fed wind turbine were also investigated, with the possible reasonable trip time of crowbar. The investigation have shown that the transient performances are closely correlated with the wind turbine drive train models, initial operational conditions, key parameters of wind turbine, and trip time of the crowbar circuit.

Keywords: Wind power, Doubly fed induction generator, Drive train, Transient performance, Crowbar

Title of the Paper:  A Fast Iterative Shrinkage-Thresholding Algorithm for Electrical Resistance Tomography


Authors: Zhang Lingling, Wang Huaxiang, Xu Yanbin, Wang Da

Abstract: Image reconstruction in Electrical Resistance Tomography (ERT) is an ill-posed nonlinear inverse problem. Considering the influence of the sparse measurement data on the quality of the reconstructed image, the l1 regularized least-squares program (l1 regularized LSP), which can be cast as a second order cone programming problem, is introduced to solve the inverse problem in this paper. A normally used method of implementing the l1 regularized LSP is based on the interior point method whose main drawback is the relatively slow convergence speed. To meet the need of high speed in ERT, the fast iterative shrinkage-thresholding algorithm (FISTA) is employed for image reconstruction in our work. Simulation results of the FISTA and l1_ls algorithm show that the l1 regularized LSP is superior to the l2 regularization method, especially in avoiding the over-smoothing of the reconstructed image. In addition, to improve the convergence speed and imaging quality in FISTA algorithm, the initial guess is calculated with the conjugate gradient method. Comparative simulation results demonstrate the feasibility of FISTA in ERT system and its advantage over the l1_ls regularization method.

Keywords: Electrical resistance tomography; l1 regularization method; interior-point method; iterative shrinkage-thresholding algorithm; linear inverse problem

Issue 12, Volume 10, December 2011

Title of the Paper:  A Novel Technique to Reduce Write Delay of SRAM Architectures


Authors: Swapnil Vats, R. K. Chauhan

Abstract: This paper presents a novel circuit technique for improving the write delay of an SRAM cell. The technique is common for all the SRAM architecture. It utilizes a PMOS between power supply rail and the SRAM cell and an NMOS between SRAM cell and ground. The simulation results for write delay, SNM and power dissipation were presented with and without application of proposed technique on two different SRAM architectures. Significant improvements on write delay and power dissipation were noticed for the proposed modified SRAM architectures with less impact on SNM.

Keywords: SRAM, SNM, NMOS, PMOS, DRAM, Butterfly curve

Title of the Paper:  Comparative Study of Three Shapes of DGS Pattern and Design of Compact Microstrip Low-Pass and Band-Pass Filters


Authors: Mouloud Challal, Frederick Labu, Mokrane Dehmas, Arab Azrar

Abstract: In this paper, three types of defected ground structure (DGS) units which are triangular-head (TH), rectangular-head (RH) and U-shape (US) are investigated and their characteristics are compared each other. Further, they are used in the design of low-pass filters (LPF) and band-pass filters (BPF) and the obtained performances are examined. The LPF employing RS-DGS geometry presents the advantages of compact size, low-insertion loss and wide stopband compared to the other filters. It provides a cutoff frequency at 2.5 GHz, a largest rejection band width of 20 dB from 2.98 to 8.76 GHz, a smallest transition region and a smallest sharpness response at the cutoff frequency. The BPF based on RS-DGS has the highest bandwidth (BW) of about 0.74 GHz and the lowest center frequency of 3.24 GHz whereas the other BPFs have BWs less than 0.7 GHz.

Keywords: Defected ground structure (DGS), low-pass filter (LPF) and band-pass filter (BPF)

Title of the Paper:  Transmission Line Protection based on Travelling Waves


Authors: Anuradha S Deshpande, Grishma S. Shah

Abstract: Major problem of tripping signal of a relay based on steady state component does not warranty faster tripping schemes for protection of extra high voltage transmission lines. Proposed work has made an attempt to find solution to the problem of fault detection and location by relay using post fault high frequency signals. Transmission line protection using travelling waves generated at the time of fault are used as trip signals of a travelling wave relay.Paper has made an attempt to obtain travelling waves components in the form of forward wave and backward waves from post fault components of voltage and current. These have been used for getting 0, á and â components using clarke’s transformation which further reduces to df and dr respectively forming trip signals for tripping travelling wave relay. The proposed methodology is tested on a 500KV test system for different types of fault and different fault locations.Results obtained by proposed methodology are in total comparison to those obtained by co-relation technique described in [1].

Keywords: Travelling waves, transmission line protection, postfault voltage, surge impedence, relaying signals

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