List of Articles
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Open Access Article
1 - A Multigate Scheme to Improve CORPL under Traffic Load in Cognitive Radio Based Smart Grids with Mesh Topology
S. A. Hashemian V. TabatabvakiliThe conventional power grid has several drawbacks and a new powerful smart grid perspective has been recently introduced. The smart grid principle, allowing to efficiently manage an electrical grid network, needs to exploit a communication network for interconnecting t MoreThe conventional power grid has several drawbacks and a new powerful smart grid perspective has been recently introduced. The smart grid principle, allowing to efficiently manage an electrical grid network, needs to exploit a communication network for interconnecting the Smart Grid devices. An increasing interest is toward wireless communications due to their higher flexibility. Within this context cognitive radio (CR) techniques has been introduced aiming to exploit more efficiently the radio spectrum resources. In neighborhood area network (NAN), mesh grids can be considered as one of possible network topologies. In such networks no base station is required and data will be sent to gateway by means of nodes themselves. Hence, routing is one of the main issues in such networks. Routing in such networks should be done by a protocol which maximizes throughput against cognitive radio drawbacks and Packets delay in such protocol needs to be minimum and suitable for smart grids applications. CORPL has been introduced as a routing protocol to meet some of these goals. In this paper by CORPL functionality would be evaluated under burst and poisson traffic. It will be shown that by increasing active nodes, CORPL functionality would be decreased. Then average upper limit for delay would be mathematically modeled and to reduce that a multigate scheme would be introduced. Manuscript profile -
Open Access Article
2 - Design and Construction of High-Current Line-Commutated Rectifier Based on Parallel Thyristors
M. Shahparasti Mohammad Farzi M. Arefian R. Asad M. Sharei-pourThis paper presents the process of designing and manufacturing a high-current line-commutated rectifier, which consists of six high current valves. Every valve is constructed through the parallelization of the four thyristors. The design of the physical structure, the p MoreThis paper presents the process of designing and manufacturing a high-current line-commutated rectifier, which consists of six high current valves. Every valve is constructed through the parallelization of the four thyristors. The design of the physical structure, the placement of busbars, and the arrangement of parallel thyristors are made using an innovative technique so that the current flows equally between them. To ensure equal flow distribution, in addition to the design of hardware structure and the use of suitable methods for simultaneous and accurate triggering of parallel thyristors, a new control technique based on the temperature measurement of each thyristor is proposed. Finally, the experimental results of a 170V, 4000A rectifier are presented to verify the proposed hardware design and control method. Manuscript profile -
Open Access Article
3 - Reliability Modeling of PV Farm Using Markov Model
V. Khaligh H. MonsefUtilization of photovoltaic units in power networks and their participation in the power supply has increased in recent years. Total world capacity of PV units has grown exponentially from 1.5 GW in 2000 to about 300 GW in 2016. This paper presents an analytical method MoreUtilization of photovoltaic units in power networks and their participation in the power supply has increased in recent years. Total world capacity of PV units has grown exponentially from 1.5 GW in 2000 to about 300 GW in 2016. This paper presents an analytical method for evaluating the reliability of large photovoltaic farms with regard to the changes in input power and reliability indices of unit components. The proposed method is not only capable of estimating the annual energy production of the photovoltaic units, but also able to calculate the system reliability indices. With Markov approach, Frequency and Duration method is utilized in order to model a photovoltaic farm similar to the multistate conventional units. Probability, frequency and transition rate of each state is obtained using the statistical data of solar radiation as well as operational characteristics of a photovoltaic unit. Due to the large number of solar radiation and PV modules operational states, k-means clustering algorithm is used for data classification. This analytical method is applied to the RBTS to demonstrate the effectiveness of developed approach. Capacity credit using LOLF index, is more than what obtained in the case of LOLE index. This observation can be explained through the variable nature of solar radiation in comparison with conventional units. Hence there is a need to obtain a model which reflects the frequency based reliability indices of PV systems. Manuscript profile -
Open Access Article
4 - Winding Losses Calculation in Multi-Winding Traction Transformer Using a Semi-Numerical Method
D. Azizian G. GharehpetianNowadays, multi-winding transformers are widely used in power systems, especially in traction networks and steel producing companies. The multi-winding transformers have special geometry. They encounter with serious problems and difficulties in design procedure in compa MoreNowadays, multi-winding transformers are widely used in power systems, especially in traction networks and steel producing companies. The multi-winding transformers have special geometry. They encounter with serious problems and difficulties in design procedure in comparison with conventional two-winding transformers. Considering the importance of windings losses (and the generated heat), the current research firstly focuses on thermal calculations in this type of transformers, also introduces a semi-numerical technique for electromagnetic analysis of split-winding traction system transformer. Combining finite element and analytical methods, the windings losses distribution due to eddy currents is calculated and the modeling results are validated using the experimental results. As shown, the introduced semi-numerical method is a powerful technique for electromagnetic modeling and winding losses calculations in split-winding transformers. Also, the winding losses of the split-winding transformer are discussed and compared to the conventional two-winding transformer results. Finally, the relation between the winding losses and frequency is studied in this paper. Manuscript profile -
Open Access Article
5 - A DC-DC Interleaved Converter Based on Buck Topology with High Step-Down Conversion Ratio
M. Ghanbari M. R. YazdaniHigh step-down conversion ratio cannot be achieved by the conventional buck converter. Also, the switch voltage stress is another drawback of the regular buck converter for high input voltages. In this paper, a DC-DC switching converter using interleaved method is propo MoreHigh step-down conversion ratio cannot be achieved by the conventional buck converter. Also, the switch voltage stress is another drawback of the regular buck converter for high input voltages. In this paper, a DC-DC switching converter using interleaved method is proposed based on the buck topology to achieve a high step-down conversion ratio. In the structure of this converter, a coupled inductor is used without need of another auxiliary winding. After presenting key waveforms and analysis of the proposed converter, the conversion ratio curves are offered. Moreover, simulation waveforms of a 240 W converter prototype with the input voltage of 150 V and the output voltage of 24 V are shown to verify the theoretical analysis. Manuscript profile -
Open Access Article
6 - Algebraic Stability Analysis and Stabilization by Proportional Controllers: Critical Inflection Point in Phase Diagram
kh. Neshat M. S. TavazoeiThis paper deals with algebraic stability analysis and investigating the existence of proportional stabilizing controllers on the basis of frequency response data. Firstly, it is shown that using the available results in this subject may yield in inconsistent subsequenc MoreThis paper deals with algebraic stability analysis and investigating the existence of proportional stabilizing controllers on the basis of frequency response data. Firstly, it is shown that using the available results in this subject may yield in inconsistent subsequences in the cases that there is a critical inflection point in phase diagram of the open-loop/process transfer function. Then, to solve this inconsistency problem some modifications are proposed. Finally, conditions for ensuring the existence of critical inflection point in phase diagram of a dynamical system are analytically found. Manuscript profile -
Open Access Article
7 - Design and ُSimulation of a New High CMRR, High Bandwidth and Low Power Current Mode Instrumentation Amplifier Based on FDCCII
S. Ahmadi S. J. AzhariIn this paper a novel topology of CMIA based on FDCCII is proposed. Due to benefiting from current mode signal processing, unlike the most of the previously reported IAs, the proposed FDCCII based structure doesn't need well-matched resistors or active blocks to obtain MoreIn this paper a novel topology of CMIA based on FDCCII is proposed. Due to benefiting from current mode signal processing, unlike the most of the previously reported IAs, the proposed FDCCII based structure doesn't need well-matched resistors or active blocks to obtain high CMRR and inherently can improve CMRR, bandwidth, power consumption and it has better frequency performances. On the other side, unlike other current mode types of this group, using fully differential structure decreases the mismatch effect in electronic blocks. Both of these advantages significantly reduced the structure size and power consumption while improving bandwidth and CMRR and makes it an excellent and an unbeatable choice for integration. In the proposed circuit, CMRR as the most important property of IA has been greatly improved by using a current subtracting stage. The CMIA has been designed using 0.18 um CMOS Technology under ±1 V supply voltages and the performance of the CMIA has been verified using HSPICE software in transistor level. The CMIA has achieved voltage CMRR of 227.4 dB, voltage CMRR bandwidth of 8.98 KHz, differential voltage gain bandwidth of 9.08 MHz and output offset voltage of 2.23 uV and the IA’s power dissipation is only 348 uW Manuscript profile -
Open Access Article
8 - A New Statistical-Physical UTD Based Channel Model for Calculating Channel Capacity in Mobile Urban Areas
Ali TajvidyIn urban areas, wireless communications suffer from severe fading due to reflections and diffraction of waves from buildings and mobility of receivers. Hence, in design of wireless networks, we need a model to predict propagation channels, in order to determine communic MoreIn urban areas, wireless communications suffer from severe fading due to reflections and diffraction of waves from buildings and mobility of receivers. Hence, in design of wireless networks, we need a model to predict propagation channels, in order to determine communication methods between transmitters and receivers. Most of current mobile wireless communication models are based on measurements. In this paper, we want to introduce a new statistical physical model in which buildings are considered as a fixed part of the model and the phenomena of diffraction and reflection are modeled using the uniform theory of diffraction (UTD).On the other hand, the receiver in this model is considered as a car. The position of this car is predicted using the Poisson point process (PPP). We can predict channel capacity in urban areas, taking into account the density of traffic and urban traffic by using this model. Furthermore, in order to validate the proposed model, we compared the results of this model with a statistical model based on measurements and there is a good agreement between them. Manuscript profile