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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
An ac to dc converter is an integral part of any power supply unit used in the all electronic equipments. These electronic equipments form a major part of load on the utility. Generally, to convert line frequency ac to dc, a line frequency diode bridge rectifier is used. To reduce the ripple in the dc output voltage, a large capacitor is used at the rectifier output. But due to this large capacitor, the current drawn by this converter is peaky in nature. This input current is rich in low order harmonics. Also, as power electronics equipments are increasingly being used in power conversion, they inject low order harmonics into the utility. Due to the presence of these harmonics, the total harmonic distortion is high and the input power factor is poor. Because of the problems associated with low power factor and harmonics, utilities will enforce harmonic standards and guidelines, which will limit the amount of current distortion allowed into the utility, and thus the simple diode rectifier may not be in use. So, there is a need to achieve rectification at close to unity power factor and low input current distortion. Initially, power factor correction schemes have been implemented mainly for heavy industrial loads like induction motors, induction heating furnaces etc., which forms a major part of lagging power factor load. Hence, PFC is becoming an important aspect even for low power application electronic equipments. There are two types of PFC"s. 1) Passive PFC, 2) Active PFC. The active PFC is further classified into low-frequency and high-frequency active PFC depending on the switching frequency. Different techniques in passive PFC and active PFC are presented here. Among these PFC"s, we will get better power factor by using high-frequency active PFC circuit. Any DC-DC converters can be used for this purpose, if a suitable control method is used to shape its input current or if it has inherent PFC properties. The DC-DC converters can operate in Continuous Inductor C
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
An ac to dc converter is an integral part of any power supply unit used in the all electronic equipments. These electronic equipments form a major part of load on the utility. Generally, to convert line frequency ac to dc, a line frequency diode bridge rectifier is used. To reduce the ripple in the dc output voltage, a large capacitor is used at the rectifier output. But due to this large capacitor, the current drawn by this converter is peaky in nature. This input current is rich in low order harmonics. Also, as power electronics equipments are increasingly being used in power conversion, they inject low order harmonics into the utility. Due to the presence of these harmonics, the total harmonic distortion is high and the input power factor is poor. Because of the problems associated with low power factor and harmonics, utilities will enforce harmonic standards and guidelines, which will limit the amount of current distortion allowed into the utility, and thus the simple diode rectifier may not be in use. So, there is a need to achieve rectification at close to unity power factor and low input current distortion. Initially, power factor correction schemes have been implemented mainly for heavy industrial loads like induction motors, induction heating furnaces etc., which forms a major part of lagging power factor load. Hence, PFC is becoming an important aspect even for low power application electronic equipments. There are two types of PFC"s. 1) Passive PFC, 2) Active PFC. The active PFC is further classified into low-frequency and high-frequency active PFC depending on the switching frequency. Different techniques in passive PFC and active PFC are presented here. Among these PFC"s, we will get better power factor by using high-frequency active PFC circuit. Any DC-DC converters can be used for this purpose, if a suitable control method is used to shape its input current or if it has inherent PFC properties. The DC-DC converters can operate in Continuous Inductor C
Author: Tine Konjedic Publisher: ISBN: Category : Languages : en Pages : 169
Book Description
This thesis investigates the possibilities for increasing the power conversion efficiency and power density of a single-phase single-stage AC-DC converter with power factor correction capability. Initially, the limitations are investigated for simultaneous increase of power density and efficiency in hard switched bidirectional converters. The switching frequency dependent turn-on losses of the transistors have been identified as the main limiting factor. In order to avoid the increase in total power losses with increasing the switching frequency, a control approach is proposed for achieving zero voltage switching transitions within the entire operating range of a bidirectional converter that utilizes power transistors in a bridge structure. This approach is based on operation in the discontinuous conduction mode with a variable switching frequency. Operation in the discontinuous conduction mode ensures the necessary reversed current that naturally discharges the parasitic output capacitance of the transistor and thus allows this transistor to be turned on at zero voltage. On the other hand, the varying switching frequency ensures that the converter operates close to the zero voltage switching boundary, which is defined as the minimum required current ripple at which zero voltage switching can be maintained. Operation with the minimum required current ripple is desirable as it generates the lowest magnetic core losses and conduction losses within the power circuit. The performance and effectiveness of the investigated approach were initially verified in a bidirectional DC-DC converter. A reliable zero voltage switching was confirmed over the entire operating range of a bidirectional DC-DC converter, as well as the absence of the reverse recovery effect and the unwanted turn-on of the synchronous transistor. In order to justify its usage and demonstrate its superior performance, the proposed zero voltage switching technique was compared with a conventional continuous conduction mode operation which is characterized by hard switching commutations. After successful verification and implementation in a bidirectional DC-DC converter, the investigated zero voltage switching approach was adapted for usage in an interleaved DC-AC converter with power factor correction capability. Comprehensive analysis of the converter's operation in discontinuous conduction mode with a variable switching frequency was performed in order to derive its power loss model. The latter facilitated the design process of the converter's power circuit. A systematic approach for selecting the converter's power components has been used while targeting for an extremely high power conversion efficiency over a wide operating range and a low volume design of the converter. The final result of the investigations performed within the scope of this thesis is the interleaved AC-DC converter with power factor correction capability. Utilization of interleaving allows for increasing the converter's power processing capability, reduces the conducted differential mode noise and shrinks the range within which the switching frequency has to vary. The proposed zero voltage switching control approach was entirely implemented within a digital signal controller and does not require any additional components within the converter's circuit. The experimental results have confirmed highly efficient operation over a wide range of operating powers. A peak efficiency of 98.4 % has been achieved at the output power of 1100 W, while the efficiency is maintained above 97 % over the entire range of output powers between 200 W and 3050 W.
Author: Mustafa Emhemed Abdulhafith Abofares Publisher: ISBN: Category : Languages : en Pages : 96
Book Description
The key objectives of this research include; design a low power bridgeless AC-DC converter with inherent power factor correction; improve the power efficiency for power electronics system with ultralow diode voltage drop; evaluate the proposed design based power factor correction for power electronics system.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Electronic equipments recently in use (PCs, TVs, and Telecommunication Equipments etc.) require power conditioning of some form, typically rectification, for their proper working. But since they have non-linear input characteristics and they are connected the electricity distribution network they produce a non-sinusoidal line current. Current of frequency components which are multiples of the natural frequency are produced that are otherwise called the line harmonics. With constantly increasing demand of these kind of equipments at a high rate, line current harmonics have become a significant problem. There has been an introduction of a lot of international standards which pose limitations on the harmonic content in the line currents of equipments connected to electricity distribution networks. This calls for measures to reduce the line current harmonics which is also otherwise known as Power Factor Correction - PFC. There exist two kinds of power factor correction techniques - passive power factor correction and active power factor correction. In this thesis we tried to devise an active power factor correction method for improvement of the power factor. In this work the advantages of a boost converter is combined with that of the average current mode control to implement the technique. UC3854 was used to design the power factor corrector. This integrated circuit had all the circuits necessary to control a power factor corrector and was designed to implement the average current mode control.
Author: Kokula Krishna Hari Kunasekaran Publisher: Association of Scientists, Developers and Faculties (ASDF) ISBN: 8192986632 Category : Computers Languages : en Pages : 114
Book Description
Proceedings of the International Conference on Interdisciplinary Research in Electronics and Instrumentation Engineering 2015 (ICIREIE)
Author: Reham Haroun Mohamed Publisher: LAP Lambert Academic Publishing ISBN: 9783659115455 Category : Languages : en Pages : 184
Book Description
Single phase high power factor rectification is the most frequently accomplished using a boost converter. The input current shaping approach results in low line currents harmonic distortion and a power factor close to unity at the interface between the ac line and the rectifier. Various techniques are available for active current shaping, average current mode control, nonlinear control and one cycle control. Most of them are now supported by dedicated integrated circuits. Average-current-mode control is the regular control where the inductor current is forced to follow the input voltage. Recently nonlinear phenomena have been obvious in AC/DC converters which results in unstable regime such as period doubling and chaos. During these operating regimes, the input current distorts and therefore, breaks the operation of PFC converters. In this book, a study for stability for the three practical controls of boost PFC converter is introduced. Each technique has been tested to determine the practical limitation for stable regions. Design guidelines are made clear for stable operation in the examined control techniques. Experimental results confirm simulation with good matching.
Author: Philip Krein Publisher: ISBN: 9780199388424 Category : Languages : en Pages : 816
Book Description
Building on the tradition of its classic first edition, the long-awaited second edition of Elements of Power Electronics provides comprehensive coverage of the subject at a level suitable for undergraduate engineering students, students in advanced degree programs, and novices in the field. It establishes a fundamental engineering basis for power electronics analysis, design, and implementation, offering broad and in-depth coverage of basic material.Streamlined throughout to reflect new innovations in technology, the second edition also features updates on renewable and alternative energy.Elements of Power Electronics features a unifying framework that includes the physical implications of circuit laws, switching circuit analysis, and the basis for converter operation and control. It discusses dc-dc, ac-dc, dc-ac, and ac-ac conversion tasks and principles of resonant converters and discontinuous converters. The text also addresses magnetic device design, thermal management and drivers for power semiconductors, control system aspects of converters, and both small-signaland geometric controls. Models for real devices and components-including capacitors, inductors, wire connections, and power semiconductors-are developed in depth, while newly expanded examples show students how to use tools like Mathcad, Matlab, and Mathematica to aid in the analysis and design of conversion circuits.Features:*More than 160 examples and 350 chapter problems support the presented concepts*An extensive Companion Website includes additional problems, laboratory materials, selected solutions for students, computer-based examples, and analysis tools for Mathcad, Matlab, and Mathematica
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Author: 
Author: Fariborz Musavi
Author: Bor-ren Lin
Author: Tine Konjedic
Author: Mustafa Emhemed Abdulhafith Abofares
Author: 
Author: Kokula Krishna Hari Kunasekaran
Author: Michael Gerard Jaskiewicz
Author: Reham Haroun Mohamed
Author: Philip Krein