Iranian Journal of Electrical & Electronic Engineering
http://ijeee.iust.ac.ir
Iranian Journal of Electrical and Electronic Engineering - Journal articles for year 2017, Volume 13, Number 2Yektaweb Collection - http://www.yektaweb.comen2017/6/11Modelling and Simulation of a Transformer With Inter-turn Fault Including Saturation Effect and Variable Fault Parameters
http://ijeee.iust.ac.ir/browse.php?a_id=993&sid=1&slc_lang=en
<p class="Abstract" style="margin: 1pt 49.55pt 0.0001pt 56.7pt; text-indent: 10.2pt; text-align: justify;">This investigation deals with a mathematical model for a distribution transformer including saturation effect. To this end, the equations related to a three phase transformer are specified and the effect of an inter-turn fault is included. Naturally by applying an inter-turn fault the inductance and resistance matrix will change. Thus, unknown quantities of inductances and resistances for completing the matrix are calculated and the inputs, outputs and state variables are specified. All the equations will be rewritten in terms of state variables, subsequently saturation effect is added to the model. Finally the block diagram of the specified model based on the obtained equations are designed and the ultimate model is simulated. The saturation effect, added to the mathematical model and also the variable fault parameters are known as two significant contributions which distinguish this study from other investigations. Various results obtained from the simulation of the final model confirm the changes in the behavior of faulty transformer such as: a large circulating current flowing in the shorted turns, lower impact on terminal voltages and currents, a sudden increase in current flowing in the primary winding, asymmetrical flux distribution and inverse proportion of the fault severity and the limiting resistor.<span style="font-size: 10pt;"><!--stripped--><!--stripped--></span></p>
<p class="Abstract" style="margin: 1pt 49.55pt 0.0001pt 56.7pt; text-indent: 10.2pt; text-align: justify;"><span style="font-size: 10pt;"><!--stripped--><!--stripped--></span></p>
<p class="Abstract" style="text-indent:10.2pt;line-height:200%"><span style="font-size: 12pt; line-height: 200%; "><!--stripped--><!--stripped--></span></p>
H. YaghobiSpace Vector Modulation Technique to Reduce Leakage Current of a Transformerless Three-Phase Four-Leg Photovoltaic System
http://ijeee.iust.ac.ir/browse.php?a_id=1037&sid=1&slc_lang=en
<p>Photovoltaic systems integrated to the grid have received considerable attention around the world. They can be connected to the electrical grid via galvanic isolation (transformer) or without it (transformerless). Despite making galvanic isolation, low frequency transformer increases size, cost and losses. On the other hand, transformerless PV systems increase the leakage current (common-mode current, (CMC)) through the parasitic capacitors of the PV array. Inverter topology and switching technique are the most important parameters the leakage current depends on. As there is no need to extra hardware for switching scheme modification, it's an economical method for reducing leakage current. This paper evaluates the effect of different space vector modulation techniques on leakage current for a two-level three-phase four-leg inverter used in PV system. It proposes an efficient space vector modulation method which decreases the leakage current to below the quantity specified in VDE-0126-1-1 standard. furthermore, some other characteristics of the space vector modulation schemes that have not been significantly discussed for four-leg inverter, are considered, such as, modulation index, switching actions per period, common-mode voltage (CMV), and total harmonic distortion (THD). An extend software simulation using MATLAB/Simulink is performed to verify the effectiveness of the modulation technique.</p>
H. RastegarRobust Adaptive Actuator Failure Compensation of MIMO Systems with Unknown State Delays
http://ijeee.iust.ac.ir/browse.php?a_id=989&sid=1&slc_lang=en
<p style="text-align: justify;">In this paper, a robust adaptive actuator failure compensation control scheme is proposed for a class of multi input multi output linear systems with unknown time-varying state delay and in the presence of unknown actuator failures and external disturbance. The adaptive controller structure is designed based on the SPR-Lyapunov approach to achieve the control objective under the specific assumptions and the SDU factorization method of the high frequency gain matrix is employed to drive the suitable form of the error equation. The two component controller structure with an integral term is used in order to compensate the effect of unknown state delay and external disturbance. Using a suitable Lyapunov-Krasovskii functional, it is shown that despite existing external disturbance and actuator failures, all closed loop signals are bounded and the plant Output asymptotically tracks the output of a stable reference model. Simulation results are provided to demonstrate the effectiveness of the proposed theoretical results.</p>
M. KamaliA Grid Connected Transformerless Inverter and its Model Predictive Control Strategy with Leakage Current Elimination Capability
http://ijeee.iust.ac.ir/browse.php?a_id=938&sid=1&slc_lang=en
<p style="text-align: justify;">This paper proposes a new single phase transformerless PV inverter for grid connected photovoltaic (PV) 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 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.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.</p>
M. SabahiDesign of High-Efficiency and Low-Cost Six-Phase Permanent Magnet Synchronous Generator for Direct-Drive Small-Scale Wind Power Application
http://ijeee.iust.ac.ir/browse.php?a_id=1009&sid=1&slc_lang=en
<p style="text-align: justify;">Permanent magnet synchronous generators (PMSG) have a huge potential for direct-drive wind power applications. Therefore, optimal design of these generators is necessary to maximize their efficiency and to reduce their manufacturing cost and total volume. In this paper, an optimal design of a six-phase 3.5 KW direct-drive PMSG to generate electricity for domestic needs is performed. The aim of optimal design is to reduce the manufacturing cost, losses and total volume of PMSG. To find the best design, single/multi-objective design optimization is carried out. Cuckoo optimization algorithm (COA) is adopted to solve the optimization problem. Comparison between the results of the single-objective and multi-objective models shows that simultaneous optimization of manufacturing cost, losses and total volume leads to more suitable design for PMSG. Finally, finite-element method (FEM) is employed to validate the optimal design, which show a good agreement between the theoretical work and simulation results.</p>
S. A. GholamianDesign of A Compact CPW-FED UWB Antenna with WiMAX and WLAN Band-Notched Characteristic Evaluated in AHP Framework
http://ijeee.iust.ac.ir/browse.php?a_id=1034&sid=1&slc_lang=en
<p><a name="OLE_LINK5"></a><a name="OLE_LINK4">In this article, we present a new design of a coplanar waveguide fed (CPW-fed) </a><a name="OLE_LINK151"></a><a name="OLE_LINK152">ultra-wideband (UWB) </a>antenna with dual band-notched characteristics. <a name="OLE_LINK17"></a><a name="OLE_LINK18">Two </a>notched frequency bands are achieved <a name="OLE_LINK62"></a><a name="OLE_LINK61">by using two </a><a name="OLE_LINK194"></a><a name="OLE_LINK243"></a><a name="OLE_LINK242">inverted U-shaped stepped impedance resonator</a>s. The proposed antenna can operate from <a name="OLE_LINK180"></a><a name="OLE_LINK179">2.82 to 11 GHz (118%),</a> defined by VSWR< 2, except two notched bands around 3.5 GHz (WiMAX) and 5.5 GHz (WLAN). The size of the antenna is <a name="OLE_LINK82"></a><a name="OLE_LINK83"></a><a name="OLE_LINK84"></a><a name="OLE_LINK85"></a><a name="OLE_LINK74"></a><a name="OLE_LINK75"></a><a name="OLE_LINK222">20×20</a>×1.6 mm<sup>3</sup>. The experimental and simulated results of the prototyped antenna, including voltage standing wave ratio (VSWR), radiation pattern, and gain characteristics are presented and discussed. In addition, Analytical Hierarchy Process (AHP) method used for comparison the proposed antenna with previous designed structures.</p>
Y. ZehforooshReal-Time Interference Detection in Tracking Loop of GPS Receiver
http://ijeee.iust.ac.ir/browse.php?a_id=963&sid=1&slc_lang=en
<p dir="ltr" style="text-align: justify;">Global Positioning System (GPS) spoofing could pose a major threat for GPS navigation ‎systems, so the GPS users have to gain a better understanding of the broader implications of ‎GPS.‎ In this paper, a plenary anti-spoofing approach based on correlation is proposed to distinguish spoofing effects. The suggested ‎method can be easily implemented in tracking loop of GPS receiver. We will study a real-time spoof recognition ‎with a clear certainty by introducing a reliable novel metric. As a primary step, the proposed technique is ‎implemented in software receiver to prove the concept of idea in a multipath-free ‎scenario. ‎Three rooftop data sets, collected in our GPS laboratory, are used in the ‎performance assessment of the proposed method. The results indicate that investigated algorithm is ‎able to perform a real-time detection in all date sets.</p>
M. R. MosaviRegulatory Impacts on Distributed Generation and Upstream Transmission Substation Expansion Planning: A Novel Stochastic Bi-level Model
http://ijeee.iust.ac.ir/browse.php?a_id=1050&sid=1&slc_lang=en
<p>In this paper, a novel framework is proposed to study impacts of regulatory incentive on distributed generation (DG) investment in sub-transmission substations, as well as upgrading of upstream transmission substations. Both conventional and wind power technologies are considered here. Investment incentives are fuel cost, firm contracts, capacity payment and investment subsidy relating to wind power. The problem is modelled as a bi-level stochastic optimization problem, where the upper level consists of investor's decisions maximizing its own profit. Both market clearing and decision on upgrading of transmission substation aiming at minimizing the total cost are considered in the lower level. Due to non-convexity of the lower level and impossibility of converting to single level problem (i.e. mathematical programming with equilibrium constraints (MPEC)), an algorithm combing enumeration and mathematical optimization is used to tackle with the non-convexity. For each upgrading strategy of substations, a stochastic MPEC, converted to a mixed integer linear programming (MILP) is solved. The proposed model is examined on a six-bus and an actual network. Numerical studies confirm that the proposed model can be used for analysing investment behaviour of DGs and substation expansion.</p>
T. Barforoushi