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#### Control of a four-switch rectifier under unbalanced input voltage

, Article PEDSTC 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2014 , p. 261-266 ; Javadian, V ; Shahbazi, M ; Zolghadri, M. R ; Sharif University of Technology
Abstract

Nowadays, reduced switch rectifiers are more interested because of less expense. Control of these rectifiers is an important part of their designing process. In this paper, a method is proposed for four-switch rectifier to continue working under unbalanced input voltage. To achieve this goal, first a method is introduced to separate positive and negative sequences of dq components. Also, the necessary condition is determined. Considering this condition, the control method is modified and new reference value for the control signals is calculated. Finally, the system is simulated in Simulink and the results are provided. These results confirm the accuracy of the developed model, and also the...

#### Modeling, control and voltage unbalance compensation in a four-switch rectifier with input power factor correction

, Article PEDSTC 2013 - 4th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2013 , Pages 148-152 ; 9781467344845 (ISBN) ; Shahbazi, M ; Zolghadri, M ; Sharif University of Technology
2013

Abstract

In this paper, a small signal model is proposed for four-switch rectifier with input power factor correction. The required transfer functions are determined and calculated for a typical rectifier. This model is used to design an appropriate controller with defined characteristic to improve the rectifier performance. Another controller is used to compensate capacitors dc voltage difference. The system is simulated in Simulink and the results are provided. These results confirm the accuracy of the developed model, and also the effectiveness of the proposed controllers

#### Ant colony optimization-based approach to optimal reactive power dispatch: A comparison of various Ant systems

, Article 2007 IEEE Power Engineering Society Conference and Exposition in Africa, PowerAfrica, Johannesburg, 16 July 2007 through 20 July 2007 ; 2007 ; 1424414784 (ISBN); 9781424414789 (ISBN) ; Hosseini, S. H ; Sharif University of Technology
2007

Abstract

The optimal reactive power dispatch (ORPD) problem is formulated as a combinatorial optimization problem involving nonlinear objective Junction with multiple local minima. In this paper, as a new approach, different ant colony optimization (ACO) algorithms are applied to the reactive power dispatch problem. Ant system (AS), the firstly introduced ant colony optimization algorithm, and its direct successors, elitist ant system (EAS), rank-based ant system (ASrank) and max-min ant system (MMAS), are employed to solve the reactive power dispatch problem. To analyze the efficiency and effectiveness of these modern search algorithms, the proposed methods are applied to the IEEE 30-bus system and...

#### Symmetrical power factors and symmetrical reactive current components

, Article 2006 IEEE Power Engineering Society General Meeting, PES, Montreal, QC, 18 June 2006 through 22 June 2006 ; 2006 ; 1424404932 (ISBN); 9781424404933 (ISBN) ; Karimi, H ; Sharif University of Technology
IEEE Computer Society
2006

Abstract

This paper deals with the definition of power factor and reactive current component in a three-phase system. For a single-phase system, power factor and reactive current component are defined based on the phase-angle displacement between the measured voltage and current waveforms. This definition can be directly extended to balanced three-phase systems. However, this extension is not suitable when the three-phase system (voltages or currents) is unbalanced. Reason is that the conventional definition of phase-angle does not directly apply to an unbalanced three-phase system and needs further refinements. This paper defines the concept of symmetrical power factors and symmetrical reactive...

#### Application of advanced SVC incase of reactive power and unbalancy compensation of a locomotive

, Article 2006 IEEE International Conference on Industrial Technology, ICIT, Mumbai, 15 December 2006 through 17 December 2006 ; 2006 , Pages 1897-1902 ; 1424407265 (ISBN); 9781424407262 (ISBN) ; Hekmati, A ; Rezaei, M. R ; Afsharnia, S ; Sharif University of Technology
2006

Abstract

This paper introduces advanced SVC. Advanced SVC has been simulated with regard to reactive power and unbalancy compensation. Then, a new space has been chosen for state equation based on combination of d-q and real space to positive - negative. By decoupling of active, reactive powers and positive, negative sequences and using decoupling circuit, the facility of each sequence control, by control circuit will be provided independently. After advanced SVC modeling, the load - which is electrification railway system - will be simulated. So a sample of electric locomotive in Iran has been investigated and simulated. By using the load model, the advanced SVC has been used for compensation of...

#### Electromagnetic-thermal design optimization of the brushless doubly fed induction generator

, Article IEEE Transactions on Industrial Electronics ; Vol. 61, issue. 4 , October , 2014 , PP. 1710-1721 ; ISSN: 02780046 ; Oraee, H ; McMahon, R. A ; Sharif University of Technology
Abstract

In view of its special features, the brushless doubly fed induction generator (BDFIG) shows high potentials to be employed as a variable-speed drive or wind generator. However, the machine suffers from low efficiency and power factor and also high level of noise and vibration due to spatial harmonics. These harmonics arise mainly from rotor winding configuration, slotting effects, and saturation. In this paper, analytical equations are derived for spatial harmonics and their effects on leakage flux, additional loss, noise, and vibration. Using the derived equations and an electromagnetic-thermal model, a simple design procedure is presented, while the design variables are selected based on...

#### A low-distortion self-oscillating power factor correction circuit for low-cost applications

, Article IEEE Transactions on Industrial Electronics ; Vol. 61, issue. 11 , 2014 , pp. 6050-6060 ; ISSN: 02780046 ; Fotowat-Ahmady, A ; Kananian, S ; Zabetian, A ; Sharif University of Technology
Abstract

Self-oscillating converters operating in the critical conduction mode are popular in low power applications because of their simplicity and low cost. However, these converters are not suited for Power Factor Correction (PFC) because the peak switch current is controlled to regulate the output voltage and does not follow the shape of the line voltage waveform. A new control circuit implementation is proposed for a self-oscillating boost converter to achieve power factor correction. A full featured design example is provided which can be simplified for use in various cost sensitive applications such as electronic lighting, etc. This wide input voltage range self-oscillating PFC prototype...

#### Calculation of confined phonon spectrum in narrow silicon nanowires using the valence force field method

, Article Journal of Electronic Materials ; Volume 42, Issue 7 , 2013 , Pages 2091-2097 ; 03615235 (ISSN) ; Neophytou, N ; Taheri, M. K ; Faez, R ; Kosina, H ; Sharif University of Technology
2013

Abstract

We study the effect of confinement on the phonon properties of ultra-narrow silicon nanowires of side sizes of 1 nm to 10 nm. We use the modified valence force field (MVFF) method to compute the phononic dispersion and extract the density of states, the transmission function, the sound velocity, the ballistic thermal conductance and boundary-scattering-limited diffusive thermal conductivity. We find that the phononic dispersion and the ballistic thermal conductance are functions of the geometrical features of the structures, i.e., the transport orientation and confinement dimension. The phonon group velocity and thermal conductance can vary by a factor of two depending on the geometrical...

#### Reactive compensation investigation of TSC systems based on different power factor definitions

, Article IECON Proceedings (Industrial Electronics Conference) ; 2012 , Pages 1393-1398 ; 9781467324212 (ISBN) ; Najmi, V ; Mokhtari, H ; Sharif University of Technology
2012

Abstract

Accurate power factor definitions are of great importance for industries due to the fact that they affect the billing strategy. They also considerably affect the generation and distribution losses of the power system. At the moment, there are some ambiguities in power definitions to be used for this purpose. In recent years, because of a rapid growth in industry and the use of variable loads such as electrical furnaces and variable speed motors, there is a need for fast compensators that are capable of tracking load changes. One of these facilities is TSC, a capacitor bank that is controlled by static switches (thyristors). In this paper, the performance of these compensators in power factor...

#### A novel control technique for Power Factor Correction in SEPIC converter utilizing input/output voltage waveforms sampling

, Article PECon 2012 - 2012 IEEE International Conference on Power and Energy ; 2012 , Pages 268-273 ; 9781467350198 (ISBN) ; Sudi, Z ; Mohagheghi, E ; Lakmehsari, A. H ; Hajihosseinlu, A ; Sharif University of Technology
2012

Abstract

In this study, a simple and novel control technique for Power Factor Correction (PFC) is introduced, which is a SEPIC-based (Single-ended Primary-inductor Converter based) rectifier with high input power factor. Operation of the proposed method is based on sampling of input and output voltages in SEPIC rectifier. Using samples of input and output voltage, this control system makes the input current to follow a sinusoidal path. As a result, the line current?'s Total Harmonic Distortion (THD) is reduced and the input power factor is improved. This paper also compares the new method with the conventional control method for the power factor correction. In order to examine the proposed control...

#### Graphene-based antidots for thermoelectric applications

, Article Journal of the Electrochemical Society ; Volume 158, Issue 12 , 2011 , Pages K213-K216 ; 00134651 (ISSN) ; Pourfath, M ; Pazoki, M ; Faez, R ; Kosina, H ; Sharif University of Technology
2011

Abstract

The low temperature thermoelectric properties of hydrogen-passivated graphene-based antidot lattices are theoretically investigated. Calculations are performed using density functional theory in conjunction with the Landauer formula to obtain the ballistic transport coefficients. Antidot lattices with hexagonal, triangular and rectangular antidot shapes are studied. Methods to reduce the thermal conductance and to increase the thermoelectric power factor of such structures are studied. Our results indicate that triangular antidot lattices have the smallest thermal conductance due to longer boundaries, the smallest distance between the neighboring antidots, and the armchair edges. This...

#### Geometrical effects on the thermoelectric properties of ballistic graphene antidot lattices

, Article Journal of Applied Physics ; Volume 110, Issue 5 , 2011 ; 00218979 (ISSN) ; Pourfath, M ; Faez, R ; Kosina, H ; Sharif University of Technology
2011

Abstract

The thermoelectric properties of graphene-based antidot lattices are theoretically investigated. A third nearest-neighbor tight-binding model and a fourth nearest-neighbor force constant model are employed to study the electronic and phononic band structures of graphene antidot lattices with circular, rectangular, hexagonal, and triangular antidot shapes. Ballistic transport models are used to evaluate transport coefficients. Methods to reduce the thermal conductance and to increase the thermoelectric power factor of such structures are studied. Our results indicate that triangular antidot lattices have the smallest thermal conductance due to longer boundaries and the smallest distance...

#### A new t-type direct AC/AC converter

, Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; February , 2015 , Pages 247-252 ; 9781479976539 (ISBN) ; Zolghadri, M. R ; Noroozi, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015

Abstract

In this paper a novel T type scheme for 1-phase direct ac/ac converters is proposed. In this topology, frequency changing takes place directly (without common DC voltage bus) through three converters that are connected in a T structure. Unity power factor and precise output voltage regulation is achieved through appropriate control of these three converters. H-bridge converters are implemented, as the basic unit, in each branches of T to make the proposed converter. The converter is controlled such that the average active power of each H-bridges remains zero. So capacitors are implemented in DC links of H-bridges. In comparison to conventional back-to-back converters, life time of each...

#### A novel control strategy for power factor corrections based on predictive algorithm

, Article PEDSTC 2010 - 1st Power Electronics and Drive Systems and Technologies Conference, 17 February 2010 through 18 February 2010, Tehran ; 2010 , Pages 117-121 ; 9781424459728 (ISBN) ; Farhangi, S ; Zolghadri, M. R ; Sharif University of Technology
2010

Abstract

A novel control strategy based on predictive control is presented for continuous conduction mode boost converter which operates as a power factor correction. In the proposed algorithm two horizons for the behavior of the circuit are predicted which improves the total harmonic distortion, mainly the low frequency harmonics. The algorithm doesn't need elaborating calculations therefore, implementation of the controller using low price processor is feasible. Moreover, an extra horizon of the prediction leads to expansion of the calculation time. Reduction of the harmonic distortion of the input current and improvement of the power factor have been demonstrated on an isolated boost PFC converter...

#### Space vector modulation for four-switch rectifier with compensating the effect of capacitors voltage ripple

, Article 2009 International Conference on Electric Power and Energy Conversion Systems, EPECS 2009 ; 2009 ; 9789948427155 (ISBN) ; Zolghadri, M. R ; Sharif University of Technology
Abstract

A space vector modulation (SVM) approach is proposed to control a four-switch rectifier with power factor correction and compensating the effect of capacitors voltage ripple. The theory and performance of this method are presented, and the method effectiveness is demonstrated by extensive simulations. The simulation results show that the capacitor voltage ripple effects in the output voltage and current shaping can be omitted and the rectifier can work agreeably under high power factor condition although capacitors voltage is not balance. The allowable amount of this unbalanced value of filter capacitors is determined

#### An isolated high power small-size interleaved full-bridge PFC rectifier for 400 volt telecom energy distribution systems

, Article 9th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2018 ; Volume 2018-January , April , 2018 , Pages 186-192 ; 9781538646977 (ISBN) ; Tahami, F ; Sharir University of Technology
Institute of Electrical and Electronics Engineers Inc
2018

Abstract

In new 400 volt energy distribution systems for telecommunication sites and data centers power density is an influential factor which is commonly desired to be provided such that the systems occupy a small space. On top of that in 400 volt energy distribution systems galvanic isolation is investigated to be inevitable. In this paper a new method is presented that makes it possible to interleave the topology of an isolated low-cost low-size rectifier in which the DC link capacitor of power factor correction stage and DC-DC stage inductor are eliminated and as result it is shown that all the benefits of interleaving such as low current ripple and higher power density are combined with the...

#### A switched-capacitor inverter with optimized switch-count considering load power factor

, Article 45th Annual Conference of the IEEE Industrial Electronics Society, IECON 2019, 14 October 2019 through 17 October 2019 ; Volume 2019-October , 2019 , Pages 4959-4964 ; 9781728148786 (ISBN) ; Tarzamni, H ; Kolahian, P ; Hosseini, S. H ; Tahami, F ; Blaabjerg, F ; Sharif University of Technology
IEEE Computer Society
2019

Abstract

In this paper, an optimized topology for switched-capacitor (SC) multilevel inverter is proposed. The proposed topology, which is referred to as Optimized Switched-Capacitor Multilevel Inverter (OSC-MI), offers a boosted staircase voltage by using only one dc source and fewer switches count. Since each industrial load requires a specific power factor (PF), an optimal converter can be designated in a way that it both satisfies the required PF and employs fewer switches and gate drivers. Therefore, the main strategy of reducing switches count in the proposed topology is to design the converter according to the required PF value. In this paper, the theoretical analytics and comparison results...

#### An isolated high power small-size interleaved push-pull PFC rectifier with ZVS for 400 volt telecom energy distribution systems

, Article 2018 IEEE International Telecommunications Energy Conference, INTELEC 2018, 7 October 2018 through 11 October 2018 ; Volume 2018-October , 2019 ; 02750473 (ISSN); 9781538653708 (ISBN) ; Chamanian, M. A ; Tahami, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019

Abstract

Power density is an influential factor in 400 volt telecom energy distribution systems. In addition, systems are desired to reach an acceptable efficiency while they take advantage of a galvanic isolation. This paper presents a new architecture that is based on push pull topology and its power switches perform ZVS in both their turn on and turn off conditions. Besides, the presented topology uses an interleaving technique that has made it desirable for high power applications. Power loss for the presented topology is calculated and compared to conventional topologies. Finally, by considering the efficiency and power density of the presented topology, it is concluded why this topology is...

#### Is the unity power factor realizable at the load terminals?

, Article IEEE Power and Energy Society 2008 General Meeting: Conversion and Delivery of Electrical Energy in the 21st Century, PES, Pittsburgh, PA, 20 July 2008 through 24 July 2008 ; 2008 ; 9781424419067 (ISBN) ; Khajehoddin, S. A ; Bakhshai, A ; Sharif University of Technology
2008

Abstract

Contrary to the widespread understanding, this paper shows by means of mathematics and numerics that a perfect power factor correction cannot be made at the load terminals only. To achieve a perfect power factor correction, the supply commitment is required as well. In the absence of such commitment, the power factor cannot reach unity unless we refine the very definition of power factor. But the refined power factor is then slightly higher than the conventional one. The refined expression for power factor is a function of the load parameters as well as the line characteristics. For an ideal power system (with no line losses), this coincides with the conventional formula. © 2008 IEEE

#### Integrated bidirectional isolated soft-switched battery charger for vehicle-to-grid technology using 4-Switch 3Φ-rectifier

, Article IECON Proceedings (Industrial Electronics Conference) ; November , 2013 , Pages 906-911 ; 9781479902248 (ISBN) ; Taghavi, M ; Tahami, F ; Oraee, H ; Sharif University of Technology
2013

Abstract

Battery and plug-in hybrid vehicles equipped with bidirectional battery chargers are capable of supplying power to the electric grid according to power system demand. This technology is called 'vehicle to grid' or V2G. A bidirectional on-board charger can be used to improve the charge availability. An on-board charger should have small size and light weight. On the other hand, the charger must minimize power quality impact, draw current at high power factor to maximize power from an outlet. In this paper, a new three-phase integrated bidirectional isolated soft-switched battery charger is proposed which is appropriate for vehicle to grid technology. The charger utilizes a 4-switch...