Iranian Journal of Electrical and Electronic Engineering

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This paper describes a DC isolated network which is fed with Distributed Generation (DG) from photovoltaic (PV) renewable sources for supplying unbalanced AC loads. The battery energy storage bank has been connected to the DC network via DC/DC converter to control the voltage of the network and optimize the operation of the PV generation units. The PV arrays are connected to the DC network via its own DC/DC converter to ensure the required power flow. The unbalanced AC loads are connected to the DC network via its own DC/AC converter. This paper proposes a novel control strategy for storage converter which has a DC voltage droop regulator. Also a novel control system based on Park rotating frame has been proposed for DC/AC converters. In this paper, the proposed operation method is demonstrated by simulation of power transfer between PV arrays, unbalanced AC loads and battery unit. The simulation results based on PSCAD/EMTDC software show that DC isolated distribution system including PV generation systems can provide the high power quality to supplying unbalanced AC loads.

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This paper presents the modeling and simulation of a proton exchange membrane fuel cell (PEMFC) generation system for off-grid and on-grid operation and configuration. A fuel cell DG system consists of a fuel cell power plant, a DC/DC converter and a DC/AC inverter. The dynamic model for fuel cell array and its power electronic interfacing are presented also a multi-input single output (MISO) DC/DC converter and its control scheme is proposed and analyzed. This DC/DC converter is capable of interfacing fuel cell arrays to the DC/AC inverter. Also the mathematical model of the inverter is obtained by using average technique. Then the novel control strategy of DC/AC inverter for different operating conditions is demonstrated. The simulation results show the effectiveness of the suggested control systems under both on-grid and off-grid operation modes.

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A fast low-power 1-bit full adder circuit suitable for nano-scale CMOS implementation is presented. Out of the three modules in a common full-adder circuit, we have replaced one with a new design, and optimized another one, all with the goal to reduce the static power consumption. The design has been simulated and evaluated using the 65 nm PTM models.

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This paper presents a novel approach for fault type estimation in power systems. The Fault type estimation is the first step to estimate instantaneous voltage, voltage sag magnitude and duration in a three-phase system at fault duration. The approach is based on time-domain state estimation where redundant measurements are available. The current based model allows a linear mapping between the measured variable and the states to be estimated. This paper shows a possible for fault instance detection, fault location identification and fault type estimation utilizing residual analysis and topology error processing. The idea is that the fault status does not change measurement matrix dimensions but changes some elements of the measurement matrix. The paper addresses how to rebuilt measurement matrix for each type of faults. The proposed algorithm is shown that the method has high effectiveness and high performance for forecasting fault type and for estimating instantaneous bus voltage. The performance of the novel approach is tested on IEEE 14-bus test system and the results are shown.

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Abstract- A novel low-voltage two-stage operational amplifier employing resistive biasing is presented. This amplifier implements neutralization and correction common mode stability in second stage while employs capacitive dc level shifter and coupling between two stages. The structure reduces the power consumption and increases output voltage swing. The compensation is performed by simple miller method. For each stage an independent common-mode feedback circuits has been used. Simulation results show that power consumption is 2.1 mW at 1V supply. The dc gain of the amplifier is about 70 dB while its output swing is as high as around 1.2V.

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This paper proposes an idea to modify the conventional Wilkinson power dividers to have physically spaced output ports. The well-known internal resistor of Wilkinson power divider is now connected to output ports by two additional transmission lines to create a triangular shape power divider. Several modified power dividers are designed at frequency of 1.0 GHz and one of them is fabricated and measured. The measured results of the fabricated diplexer have very good agreement with the theoretical results.

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The characteristics of dielectric backed planar conducting layers of arbitrarily shaped in a rectangular waveguide are calculated by means of coupled integral equation technique (CIET) which accurately takes higher order mode interactions. Equivalent structures for the accurate analysis whole structure are introduced in which magnetic surface currents are identified as the unknowns at the aperture parts of interfaces in all regions. Spectral dyadic green’s functions are derived for these equivalent structures. A coupled magnetic filed integral equation formulation is proposed which is solved using method of moment (MoM). Then one matrix equation that involves the all magnetic currents of non metallic parts (aperture parts) of discontinuities is derived. This single matrix formulation replaces the procedure of cascading individual GSM’s of each block. By dividing the area of cross section in discontinuities into a given number of subsections, it is possible to model any shape of metallic parts. In this method when the shape of metallic parts (in a given structure) changes, the related coupled integral equations can be extracted from the pre-computed general matrices in a given frequency and there is not need to repeat the all of process. The proposed technique permits modeling of a variety of structures such as cavity-backed micro strip antenna, frequency selective surfaces (FSS’s), waveguide filters with printed irises and generally multilayered media with printed circuits embedded between dielectric layers in a waveguide. The usefulness of the proposed method and its performance are verified by calculating and simulating of a given structure.

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Recently several robust control designs have been proposed to the load-frequency control (LFC) problem. However, the importance and difficulties in the selection of weighting functions of these approaches and the pole-zero cancellation phenomenon associated with it produces closed loop poles. Also the order of robust controllers is as high as the plant. This gives rise to complex structure of such controllers and reduces their applicability in industry. In addition conventional LFC systems that use classical or trial-and-error approaches to tune the PI controller parameters are more difficult and time-consuming to design. In this paper, a bisection search method is proposed to design well-tuned PI controller in a restructured power system based on the bilateral policy scheme. The bisection search is a very simple and rapidly converging method in mathematics. It is a root-finding approach which repeatedly bisects an interval and then selects a subinterval in which a root must lie for further processing. The new optimized solution performance has been applied to a 3-area restructured power system with possible contracted scenarios under large load demand and area disturbances. The results evaluation shows the proposed method achieves good performance compared with a powerful robust ILMI-based controller. Moreover, this newly developed solution has a simple structure, and is fairly easy to implement in comparison to other controllers, which can be useful for the real world complex power systems.

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In this article, three new green's functions are presented for a narrow strip line (not a thin wire) inside or on a homogeneous dielectric, supposing quasi-TEM dominant mode. These functions have no singularity in contrast to so far presented ones, so that they can be used easily to determine the capacitance matrix of multi-layer and single-layer homogeneous coupled microstrip lines. To obtain the green’s functions, the Laplace’s equation is solved analytically in Fourier integral or Fourier series expressions, taking into account the boundary conditions including the narrow strip. The validity and accuracy of three presented green’s functions are verified by some examples.

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A dual-band artificial magnetic material and then a dual-band double-negative metamaterial structure based on symmetric spiral resonators are presented. An approximate analytical model is used for the initial design of the proposed structures. The electromagnetic parameters of the proposed metamaterial structure retrieved using an advanced parameter retrieval method based on the causality principle show its dual-band nature at microwave frequencies.

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The matrix converter instability can cause a substantial distortion in the input currents and voltages which leads to the malfunction of the converter. This paper deals with the effects of input filter type, grid inductance, voltage fed to the modulation algorithm and the synchronous rotating digital filter time constant on the stability and performance of the matrix converter. The studies are carried out using eigenvalues of the linearized system and simulations. Two most common schemes for the input filter (LC and RLC) are analyzed. It is shown that by a proper choice of voltage input to the modulation algorithm, structure of the input filter and its parameters, the need for the digital filter for ensuring the stability can be resolved. Moreover, a detailed model of the system considering the switching effects is simulated and the results are used to validate the analytical outcomes. The agreement between simulation and analytical results implies that the system performance is not deteriorated by neglecting the nonlinear switching behavior of the converter. Hence, the eigenvalue analysis of the linearized system can be a proper indicator of the system stability.

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A method for design and implementation of a compact via-less Composite Right/Left-Handed Transmission Line (CRLH TL) is presented. By introducing a new circuit model, the CRLH transmission line behavior is studied versus the parameters variations to achieve the desired characteristic impedance and electrical length. Then a compact quarter wavelength CRLH transmission line with 70 Ω characteristic impedance is designed as an example. Finally a very compact four way Wilkinson power divider and a rat-race coupler are designed and fabricated by using this type of CRLH TL which exhibit about 75% and 80% compactness, respectively.

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The ideal analysis of planar diodes in Temperature Limited Region is presented. Two types of relations are obtained for electric potential and electric field distributions one accurate but implicit and the other almost accurate but explicit.

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Multi agent systems (MAS) are popularly used in practice, however; a few studies have looked at MAS capabilities from the power engineering perspective. This paper presents the results of an investigation concerning the compatibility of MAS capabilities in different power engineering categories. Five MAS capabilities and seven power system categories are established. A framework for applying MAS in power engineering is developed. A fuzzy inference system is adopted to evaluate the paper proposed framework. Two approaches, namely simulation and real, are considered for different power categories. The paper shows that MAS capabilities are generally compatible with both approaches, although compatibility of MAS with real approach is more significant. The paper concludes that in the near future MAS is anticipated to be a key important tool in the development of intelligent systems and smart grids in power system. This paper contributes to thinking on perspective of MAS in power System.

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This paper proposes a new single phase transformerless Photovoltaic (PV) inverter for grid connected systems. It consists of six power switches, two diodes, one capacitor and filter at the output stage. The neutral of the grid is directly connected to the negative terminal of the source. This results in constant common mode voltage and zero leakage current. Model Predictive Controller (MPC) technique is used to modulate the converter to reduce the output current ripple and filter requirements. The main advantages of this inverter are compact size, low cost, flexible grounding configuration. Due to brevity, the operating principle and analysis of the proposed circuit are presented in brief. Simulation and experimental results of 200W prototype are shown at the end to validate the proposed topology and concept. The results obtained clearly verifies the performance of the proposed inverter and its practical application for grid connected PV systems.

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