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Open Access Article
1 - Analysis of Hybrid Reference Frame Limiting Strategy Performance in the Presence of Secondary Control of Inverter Based Islanded Microgrids
Iman SadeghkhaniWith increasing the capacity and number of distributed energy resources (DERs), it is necessary to keep them connected to the microgrid during the disturbances. Two of the most important measures for satisfying this requirement are to provide the high quality voltage fo MoreWith increasing the capacity and number of distributed energy resources (DERs), it is necessary to keep them connected to the microgrid during the disturbances. Two of the most important measures for satisfying this requirement are to provide the high quality voltage for feeding the critical loads and to limit the electronically-coupled DERs current and voltage. This paper investigates the performance of hierarchical control structure of islanded microgrids during and after the fault conditions. The primary control level of this control structure is equipped with the hybrid reference frame limiting strategy to limit the voltage-sourced converter (VSC) current and voltage. The effect of employing the concept of independent control of natural reference frame in both primary and secondary control levels and the influence of using the conditional integration method in the voltage controller of secondary control level on the microgrid performance during and after fault condition are investigated. The study results are demonstrated through several time-domain simulations of symmetrical and asymmetrical faults. Manuscript profile -
Open Access Article
2 - Design and implement of a high step-up boost converter with voltage multiplier
Sadegh Heidari Beni Mohammad Mehdi MirtalaeeBecause the traditional fossil energy is not renewable modern societies, are facing energy shortages. As a result, it is necessary to develop new energy that is clean and renewable to replace of fossil fuels. Solar energy, photovoltaic power generation, fuel cell and hy MoreBecause the traditional fossil energy is not renewable modern societies, are facing energy shortages. As a result, it is necessary to develop new energy that is clean and renewable to replace of fossil fuels. Solar energy, photovoltaic power generation, fuel cell and hydrogen energy are methods used to big - scale energy sources.In a mono - phase system with two - step structure if the line voltage is 220 volts, bus inverter voltage that connected to network, should be about 380 volts. However, the output voltage of the photovoltaic cells and fuel cells are generally between 25 to 40 volts this voltage is much lower than the bus voltage. So a high efficiency DC-DC converter output voltage is required to boost fuel cells and photovoltaic cells. In this research, will be presented an improved structure as high efficiency voltage boost converter with a voltage multiplier circuit for solar cell applications. In the proposed structure for efficiency improvement, used voltage multiplier circuit techniques and coupled inductors. We have the proposed converter using the active clamp circuit to achieve soft switching conditions and reduce switching losses. generally, the advantages of the proposed converter are high step-up voltage and high efficiency, low voltage stress for switches and diodes, providing soft switching conditions, and ultimately reducing the number of magnetic elements and the circuit's size. In this paper, in addition to describing the operation of the circuit and provide theoretical analyzes, validity of circuit performance will be evaluated through simulation software Manuscript profile -
Open Access Article
3 - Ultra low voltage and low power 4-2 compressor using FinFET transistors
Amir Baghi Rahin Vahid Baghi RahinA compressor is basic building blocks of many arithmetic circuits. Design of smaller area, low power consumption and high speed compressor is always in demand. As the channel length approaches nanometer scale, the use of MOSFET as the basic device in compressor now has MoreA compressor is basic building blocks of many arithmetic circuits. Design of smaller area, low power consumption and high speed compressor is always in demand. As the channel length approaches nanometer scale, the use of MOSFET as the basic device in compressor now has reaching its performance limits such as average power dissipation and speed. In this paper, a 1-bit full adder cell using FinFET transistor based on PTM 32nm process model with 0.6 V supply voltage for mobile applications is proposed. Then, the proposed full adder cell is used in the structure of compressor and performance of the proposed 4: 2 compressor is evaluated with the simulation results obtained from HSPICE. The main parameters of proposed compressor such as power compression, delay, power-delay product (PDP) and energy-delay product (EDP) were measured and its superior performance has been proved by various simulations. Also, in comparison of MOSFET based compressor, the number of transistors is decreased to 42. Manuscript profile -
Open Access Article
4 - Improved Angular Tracking Accuracy in Phased Array Radar
Ehsan Asgari Mojdeh Mahdavi Ruhollah HafezifardMonopulse is a technique which is used to detect radiation direction of waves. Radiation can be originated from active sources such as radar antennas, disturbances, etc., or passive sources, such as the reflector plates of an aircraft. Nowadays, monopulse technique has MoreMonopulse is a technique which is used to detect radiation direction of waves. Radiation can be originated from active sources such as radar antennas, disturbances, etc., or passive sources, such as the reflector plates of an aircraft. Nowadays, monopulse technique has been used in many modern radar systems. In radar tracking accuracy, the criterion for evaluating the angulation function is the differential gradient. It needs to have accurate information about antenna dimensions and wavelengths. In this paper, the difference gradient value is normalized and can be completed with knowing the radiation pattern of the antenna without knowing wavelength and gate dimensions. Then, by choosing a four-horns feed, the feed is optimized based on the squint angle. The results indicate that in the whole functional range, the optimum squint angle has the least angular error. Simulations provide us with confidence in the superior performance of the radar tracker with an optimal squint angle for all target angles within the range of the pattern of monopulse radar. Manuscript profile -
Open Access Article
5 - Design and Fabrication of Novel Single- and Dual-band Bandpass Filters with Modern Zero-Degree Feed Structure for Wireless Communications
Mohammad Reza Zobeyri Ahmadreza EskandariIn this paper, there are three novel bandpass filters (BPFs), consist of single- and dual-band, presented in a same size, which all the filters, have been designed, optimized and finally fabricated and measured, based on a primary structure and using planar microstrip t MoreIn this paper, there are three novel bandpass filters (BPFs), consist of single- and dual-band, presented in a same size, which all the filters, have been designed, optimized and finally fabricated and measured, based on a primary structure and using planar microstrip technology. Each of the generated passbands, is resonated by the use of one of the two existing types of resonator structures. The larger resonators, as main-structures of the filter with a stepped-impedance features, by appling 0°-feed structure and electrical coupling in-between, create the first passband at 0.9 GHz. The smaller resonators as sub-structures, with dual-spiral topology, are in the same size and uniform-impedance, and with symmetrical feeding and internal coupling, are embedded in the main-structures to generate and control the higher passband at 1.8GHz. The existence of a cross-coupling between the sub-structures, suppresses any harmonics in the stop-band and generates additional transmission zeros on both sides of the upper passband. Overal dimensions of the innovative filters with a miniaturizing approach, are reduced from 0.163λg*0.09λg to 0.092λg*0.08λg in terms of the guided wavelength, which is the most compacted structure compared with other filters. According to 0.7 dB and 0.5 dB, the obtained insertion losses of the first and second passbands of the dual-band BPF respectively, the lowest losses have been achieved, compared with other examined dual-band BPFs. Finally three prototypes for global systems for mobile communication, were fabricated and measured. A good agreement between the measured and simulated results indicates realizing the goals and ingenious methods of this design. Manuscript profile -
Open Access Article
6 - Analysis of Bifurcation Phenomenon in a Grid-Connected Electric Arc Furnace
Mohammad Behzad Es-haghi Mehran ZamanifarThis paper aims to study the stability and dynamic behavior of a grid-connected electricarc furnace system, using bifurcation theory. This theory introduces a systematic method for stability analysis of dynamic systems, under changes in the system parameters. In fact, a MoreThis paper aims to study the stability and dynamic behavior of a grid-connected electricarc furnace system, using bifurcation theory. This theory introduces a systematic method for stability analysis of dynamic systems, under changes in the system parameters. In fact, a parameter is constantly changed in each step, using MATLAB and/or AUTO software, and system eigenvalues are monitored simultaneously. Considering how the eigenvalues approach the system’s imaginary axis on S plain in accordance with the changes in the targeted parameter, the occurred saddle-node and/or Hopf bifurcation of the system is extracted. In this paper, at first, electric arc furnace is modeled by the differential-algebraic equations and then based on the projection method, two-dimensional center manifold at the Hopf bifurcation happens in the electric arc furnace system is achieved analytically. Projection method is discussed in the bifurcation theory and is presented totally in this paper. Finally, the results are compared by the computer simulations. Manuscript profile
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