ترانسفورماتور

Open Access Article

1 - بررسي موانع همكاري صنعت و دانشگاه و معرفي يك نمونه‌ی موفق در ايران
Mohammad kabiri karim miralikhani hooshang aliverdilou

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Open Access Article

2 - Determination of Control Variables in Power Systems to Maximum Load Restoration
H. Afrakhte A. Yazdian Varjani

This paper presents a new method to maximize load restoration in faulted condition in power systems. Control variables which are used to restore maximum load include tap of power transformers, generation rescheduling, and load shedding in the worst case. Modeling is don More

This paper presents a new method to maximize load restoration in faulted condition in power systems. Control variables which are used to restore maximum load include tap of power transformers, generation rescheduling, and load shedding in the worst case. Modeling is done in three stages with various control variables arrangements. In the first stage of modeling, power transformer tap is used as a control variable. In the second stage, power transformers taps and generations rescheduling are considered. In the last stage, load shedding as another variable is added to decision variable spaces. Since the number of variables is high and final solution space can be nonlinear, genetic algorithm is used in the optimization process. The capabilities of the proposed method were assessed using IEEE-RTS test system with satisfactory results. Manuscript profile

Open Access Article

3 - Transformers Oil Static Electrification Analysis by Using Open Cycle System
B. vahidi Gh. Rasuli Hashemabad

Static electrification due to oil flow is the main reason for several electrical breakdown in large transformers. In the present paper this phenomenon has been investigated by the aid of open cycle system. Finally from tests results obtained by authors, the effects of a More

Static electrification due to oil flow is the main reason for several electrical breakdown in large transformers. In the present paper this phenomenon has been investigated by the aid of open cycle system. Finally from tests results obtained by authors, the effects of applied electric field, temperature and oil flow velocity on static electrification have been investigated. Manuscript profile

Open Access Article

4 - A Novel Wavelet Based Method for Improvement of Power Transformer Differential Relay against Magnetizing Inrush Current and CT Saturation
A. Rahmati M. Sanaye-Pasand

Differential protective relay serves as the main protection of transformers against faults in the windings for many years. Unremitting tries for more smart of this protection relay have been done by different creative manufactures and up to now different methods and inv More

Differential protective relay serves as the main protection of transformers against faults in the windings for many years. Unremitting tries for more smart of this protection relay have been done by different creative manufactures and up to now different methods and inventions have been proposed for better operational of the differential relay. However, a differential protection for differential currents would be handicapped by difficulties due to several natural phenomena which are the cause of false differential currents and misoperate of the relay. Some of these phenomena, such as the inrush current and saturation of instrument current transformers, are the main concern in designing an efficient differential protection algorithm. This paper at first, proposes a new algorithm based on the Wavelet Transform (WT) to identify internal fault from magnetizing inrush in three phase power transformers. The internal faults can be accurately discriminated from inrush current less than a quarter a cycle after the disturbance. At following with definition of an index which it is extracted from the high frequencies by WT, the restrain current in bias-current characteristic of differential relay has been improved. Obtained results demonstrate that the proposed algorithm can provide the desired response and can be used as a very fast and accurate method. Manuscript profile

Open Access Article

5 - Determination of a New Model for Investigating Ultra-Saturation Phenomenon during the Enegization of the Loaded Three-Phase Power Transformer and Its Effect on Differential Protection
B. Noshad M. Razaz S. Gh. Seifossadat

One of the mal-operation of the power transformer differential protection that may occur during the energization of a loaded power transformer is the ultra-saturation phenomenon. In this paper, a new model to study the ultra-saturation phenomenon during the energizaton More

One of the mal-operation of the power transformer differential protection that may occur during the energization of a loaded power transformer is the ultra-saturation phenomenon. In this paper, a new model to study the ultra-saturation phenomenon during the energizaton of a loaded three-phase power transformer is presented and its effect on the differential protection of the power transformer is considered. For modeling of the ultra-saturation phenomenon, the nonlinear characteristic of the transformer core and the saturation effect of current transformers are considered. It is assumed that the load of the power transformer is a resistive and an inductive load. The mal-operation of the differential protection depends on a variety of factors the most important parameters of which are inception angle and residual flux. In this paper the parameters mentioned will study in different cases. In this paper, simulation is done by MATLAB program. Manuscript profile

Open Access Article

6 - A New Unified Power Quality Conditioner based on Trans-Z-Source Inverter
M. Siahi Mohammad Davoodi

Unified Power quality conditioner (UPQC) consists of back to back voltage source inverters. In UPQC combination of parallel and series active power filters are used to compensate for the nonlinear load current harmonics and voltage distortions, simultaneously. For appro More

Unified Power quality conditioner (UPQC) consists of back to back voltage source inverters. In UPQC combination of parallel and series active power filters are used to compensate for the nonlinear load current harmonics and voltage distortions, simultaneously. For appropriate performance of both converters and bidirectional power flow, the DC link voltage should be at least 1.41 times larger than the line to line voltage in the high voltage part of the system; i.e. the parallel active filter. One of the determining factors for the cost of semiconductors is the maximum tolerable voltage stress. The voltage stress of the series converter increases when the DC link voltage is high. In order to overcome this deficiency, a Z-source network is added to the common structure of back to back invertors in the UPQC. It will reduce the applied DC voltage to the series active power filters significantly and decrease the cost of manufacturing. In this structure, an impedance source network is used in an AC/DC inverter to produce a buck-boost effect. Additionally, dead time has been eliminated through the use of a Z source network in the parallel active filter and thus its performance and reliability has increased impressively. In this paper, a comparison study has been conducted through necessary simulations for the performance evaluation of the common and proposed structures. The total switching device power has been used as a criteria to confirm the manufacturing cost reduction in the proposed structure. Manuscript profile

Open Access Article

7 - An Improved Grid Connected Transformerless Inverter with Proportional Resonant Controller
J. Fallah Ardashir M. Sabahi S. H. Hosseini E. Babaei G. Gharehpetian

The grid tied PV systems without transformer have some benefits such as low cost, weight and size and also increases the overall efficiency. The galvanic connection between the grid and PV system causes leakage current in the transformerless inverter to flow through pa More

The grid tied PV systems without transformer have some benefits such as low cost, weight and size and also increases the overall efficiency. The galvanic connection between the grid and PV system causes leakage current in the transformerless inverter to flow through parasitic capacitors between the PV system and ground and causes personal safety problems, increases the output harmonic spectrum, and system losses. This paper introduces a modified single phase two stage transformerless inverter for grid connected photovoltaic systems with low leakage current. The neutral of the grid is directly connected to the negative terminal of PV panel that eliminates leakage current without complex control strategy. In this paper, a Proportional Resonant (PR) control strategy is used to control the injected current. The performance of the transformerless inverter is analyzed and its structure has been simulated in PSCAD/EMTDC and the obtained results tested experimentally. Manuscript profile

Open Access Article

8 - Operational Analysis of the Buck Boost DC–DC Converter with High Step-Up Voltage Gain
M. R. Banaei H. A. Faeghi Bonab

In some applications that we need a high voltage gain such as the photovoltaic cell and fuel cell, high step up dc-dc converters must be used, but conventional boost converter cannot provide the high voltage gain. For this reason, in this paper, a single switch transfor More

In some applications that we need a high voltage gain such as the photovoltaic cell and fuel cell, high step up dc-dc converters must be used, but conventional boost converter cannot provide the high voltage gain. For this reason, in this paper, a single switch transformerless high step-up buck boost dc-dc converter with reduced voltage stress on the semiconductors is proposed. The proposed converter has higher voltage gain in step-up mode in comparison with conventional boost and buck-boost converters. Reduced voltage stress on the active switch allows to choose lower voltage rating MOSFETs to reduce both switching and conduction losses. Low voltage stress on the diodes allows the use of Schottky rectifiers for alleviating the reverse-recovery current. The proposed converter can be operated in the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). In this paper, different operation modes of the proposed converter, calculation of the voltage gain, the currents that flow through the components, efficiency and capacitors voltage ripple are presented. To verify the operation of the proposed converter, simulation results via PSCAD software and experimental results are provided. Manuscript profile

Open Access Article

9 - Evaluation of the Effect of Transformer Oil Parameters on the Transformer Health Index Using Curve Estimation Method
Morteza Saeid Hamed Zeinoddini-Meymand

Transformers are one of the most expensive and important equipment in power systems that are under the influence of electrical, thermal and chemical reactions The transformer health index is a standard that is used to evaluate the condition and determine the remaining l More

Transformers are one of the most expensive and important equipment in power systems that are under the influence of electrical, thermal and chemical reactions The transformer health index is a standard that is used to evaluate the condition and determine the remaining life of the transformer by using laboratory data and field inspections. The purpose of this article is to determine the relationships between electrical, physical, chemical parameters of oil, dissolved gases in oil and transformer health index. One of the advantages of using the regression method in the analysis of transformer data compared to other methods for determining the transformer health index is determining the influence of the parameters that have the greatest impact on each other. In this article, Curve Estimation Regression method is used and the results are drawn by drawing graphs by SPSS statistical software to analyze the parameters. To carry out the simulations, the laboratory data of some transformers have been considered. Manuscript profile

Open Access Article

10 - Integrated Modeling of Bidirectional Solid-State Transformers: Rectifier, DC to DC Converter and Inverter Stages
hamed molla-ahmadian morteza shafiei javid khorasani

: One of the new and growing equipment in modern power networks is solid state or power electronic transformer. These types of transformers are based on power semiconductor switches and high frequency transformers. Compared to traditional transformers, it has several ca More

: One of the new and growing equipment in modern power networks is solid state or power electronic transformer. These types of transformers are based on power semiconductor switches and high frequency transformers. Compared to traditional transformers, it has several capabilities such as the ability to operate with input voltage variations in amplitude and frequency, automatic regulation of output voltage and input power factor correction. The investigated transformer has the ability to transfer power in both directions and has three stages, including the rectifier, the middle stage and the inverter stage. This transformer has a large number of semiconductor switches and its modeling, analysis, design and simulation is difficult and complex. In particular, real-time simulation of these transformers with conventional models is not possible. In these cases, the use of averaging theory seems to be the appropriate solution. In this paper, the averaging theory is applied to a solid-state transformer and its modeling is done in a simple and powerful way with the ability to study real-time, transient and steady states performance. The proposed modeling includes differential equations and equivalent circuits and offers an integrated transformer model with the ability to study the interaction between stages as a part of power system. The presented models are used in simulation of smart grids, DC microgrids and connection of distributed generation sources to the grid, as well as analysis and design of solid-state transformer behavior in areas such as renewable energies and electrical transportation. In addition to the proposed modeling, the closed-loop control structure has been implemented for all three stages. Transformer simulation is performed by implementing differential equations in SIMULINK/MATLAB software and verified the proposed model. Manuscript profile

Open Access Article

11 - Investigating the three-phase to five-phase time converter using a special transformer connection
Ali Bahadran Seyed Majid Keshavarz

The first five-phase induction motor drive systems were proposed in the late 1970s for variable speed drive applications. Since then, considerable research efforts have been devoted to identifying the development of commercially feasible multiphase propulsion systems. S More

The first five-phase induction motor drive systems were proposed in the late 1970s for variable speed drive applications. Since then, considerable research efforts have been devoted to identifying the development of commercially feasible multiphase propulsion systems. Since the three-phase supply is available from the network, it is necessary to remove a static phase conversion system to obtain a multi-phase supply from the existing three-phase supply. Therefore, this paper presents a new transformer connection scheme to convert a three-phase network power supply into a five-phase constant voltage and constant frequency supply. The proposed transformer connection gives a five-phase output and therefore, can be used in applications that require a five-phase power supply. Currently, the five-phase motor drive is commercially viable. The five-phase transmission system solution can be further explored as an efficient solution for bulk power transmission. The connection scheme is explained using simulation and experimental approach to prove the feasibility. The geometry of the manufactured transformer is explained in this article. Manuscript profile

Open Access Article

12 - Investigating the performance of electronic transformers on the environment
Maziar Demory Nejad Mehrdad Mohadpur

During the last 30 and 40 years, TS transformer substations have evolved a lot, from the classic assembly in open areas, partition walls and outdoors, to the existing model, in order to increase human safety and material reliability, as well as significant progress. Ass More

During the last 30 and 40 years, TS transformer substations have evolved a lot, from the classic assembly in open areas, partition walls and outdoors, to the existing model, in order to increase human safety and material reliability, as well as significant progress. Assembly and space reduction, new results such as metal enclosures, prefabricated buildings, compact transformer substations and finally installed substations are also revolutionary. Due to society's increasing concern about the environment, the industry as a whole is rethinking the design and materials that may mean pollution, trying to replace them as much as possible with environmentally friendly communities. The inevitable development of society cannot and should not destroy the future of the earth. The time for sustainable development has come. So our work here today is a help in that sense. Manuscript profile

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