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Jahan H.K.,Iran Power Generation, Transmission and Distribution Management Co. | Banaei M.R.,Shahid Madani University of Azarbaijan
IET Power Electronics | Year: 2014

In this study, a three-phase to three-phase matrix converter with eight switches in each phase is presented. In addition, a simple switching strategy is used to control switches based on the comparison of a reference output voltage value with 12 voltage values obtained from input voltage. One advantage of the simple switching approach is that it is suitable to step down input voltage frequency. So, it is applicable to interface microturbine generation and load. This converter can boost input voltage amplitude with variable reduced frequency with respect to conventional matrix converter using a simple switching technique. Other advantages of the suggested converter is that it is possible to obtain a voltage with low total harmonic distortion by applying the stated switching method as compared to conventional matrix converter. Simulation and experimental results are shown to validate the capability of the suggested converter in the boosting of input voltage at a variable frequency. © The Institution of Engineering and Technology 2014. Source

Fallahi A.,Iran Power Generation, Transmission and Distribution Management Co. | Ebrahimi R.,Iran University of Science and Technology | Ghaderi S.F.,University of Tehran
Energy | Year: 2011

This paper provides an empirical analysis of the determinants of energy efficiency in 32 power electric generation management companies over the period 2005-2009. The study uses non-parametric Data Envelopment Analysis (DEA) to estimate the relative technical efficiency and productivity change of these companies. In order to verify the stability of our DEA model and the importance of each input variable, a stability test is also conducted. The results of the study indicate that average technical efficiency of companies decreased during the study period. Nearly half of the companies (14) are below this average level of 88.7% for five years. Moreover, it is shown that the low increase of productivity changes is more related to low efficiency rather than technology changes. © 2011 Elsevier Ltd. Source

Iman-Eini H.,University of Tehran | Farhangi S.,University of Tehran | Schanen J.-L.,Grenoble Institute of Technology | Khakbazan-Fard M.,Iran Power Generation, Transmission and Distribution Management Co.
Journal of Power Electronics | Year: 2010

Reliability is an important issue in cascaded H-bridge converters (CHB converters) because they use a high number of power semiconductors. A faulty power cell in a CHB converter can potentially lead to expensive downtime and great losses on the consumer side. With a fault-tolerant control strategy, operation can continue with the undamaged cells; thus increasing the reliability of the system. In this paper, the operating principles and the control method for a CHB multilevel rectifier are introduced. The influence of various faults on the CHB converter is investigated. The method of fault diagnosis and the bypassing of failed cells are explained. A fault-tolerant protection strategy is proposed to achieve redundancy in the CHB rectifier. The redundant H-bridge concept helps to deal with device failures and to increase system reliability. Simulation results verify the performance of the proposed strategy. Source

Rezaei S.,Iran Power Generation, Transmission and Distribution Management Co.
2015 IEEE 15th International Conference on Environment and Electrical Engineering, EEEIC 2015 - Conference Proceedings | Year: 2015

Catastrophic circumstances and equipment failures in electrical networks are mostly caused by emerging unidentified phenomena. Resonance and Ferroresonance are those phenomena, which have been investigated since, many years ago. Manitoba Hydro 230 kV electrical network has experienced Ferroresonant states several times. Such conditions may occur in effect of short circuit, breaker phase failure, transformer energizing, load rejection, accidental or scheduled line disconnection, and plant outage. One of the significant consequences of resonant and Ferroresonant states can be an apparent mis-operation or tripping some protective devices and inaccurate operation of instrument transformers. In this paper by means of PSCAD/EMTDC simulation software, Ferroresonant states are analyzed in Manitoba Hydro 230 kV network. Ferroresonant states are classified in to adequate modes by Ferroresonance detection tools, furthermore; kinds of protective relays subjected to Ferroresonance are simulated in the power network, and operation of relays is assessed. © 2015 IEEE. Source

Samimi M.H.,University of Tehran | Mahari A.,University of Tehran | Farahnakian M.A.,Iran Power Generation, Transmission and Distribution Management Co. | Mohseni H.,University of Tehran
IEEE Sensors Journal | Year: 2014

The Rogowski coil is an old device for current measurement. It has been modified and improved over a century and is still being studied for new applications. The Rogowski coil has various advantages over conventional magnetic current transformers (CTs). Not only can it be used instead of CT, but also it has various utilizations in other fields. This paper provides a brief review on different aspects of the Rogowski coil and its advancement procedure, during last decades. In this paper, the history of the coil is brifely reviewed and its bases and applications are discussed. The Rogowski coil is analyzed from different points of view, including different integration techniques in the output stage, models for the Rogowski coil, experimental methods for parameter measurement in models, and method for determining the damping resistor. Finally, a brief review over different applications of the coil ends this paper. © 2001-2012 IEEE. Source

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