PFC Topologies for AC to DC Converters in DC Micro-Grid

With increasing dominance of renewable energy resources and DC household appliances, the novelty of DC micro grid is attracting significant attention. The key interface between the main supply grid and DC micro grid is AC to DC converter. The conventional AC to DC converter with large output capacitor introduces undesirable power quality problems in the main supply current. It reduces system efficiency due to low power factor and high harmonic distortion. Power Factor Correction (PFC) circuits are used to make supply currents sinusoidal and in-phase with supply voltages. This paper presents different PFC topologies for single phase AC to DC converters which are analyzed for power factor (PF), total harmonic distortion (THD) and system efficiency by varying output power. Two-quadrant shunt active filter topology attains a power factor of 0.999, 3.03% THD and 98% system efficiency. Output voltage regulation of the presented active PFC topologies is simulated by applying a step load. Two-quadrant shunt active filter achieves better output voltage regulation compared to other topologies and can be used as grid interface

A comparative study of electric power distribution systems for spacecraft

The electric power distribution systems for spacecraft are compared concentrating on two interrelated issues: the choice between dc and high frequency ac, and the converter/inverter topology to be used at the power source. The relative merits of dc and ac distribution are discussed. Specific converter and inverter topologies are identified and analyzed in detail for the purpose of detailed comparison. Finally, specific topologies are recommended for use in dc and ac systems

Kesan penularan wabak Covid-19 terhadap sektor perumahan dari perspektif kemampuan pemilikan rumah

Rumah menjadi hak setiap individu seperti termaktub dalam Universal Declaration of Human Rights 1948 : Everyone has a right to a standard of living adequate for the health and well-being of himself and of his family, including food, clothing, housing and medical care and necessary social services and the right to security in the event of unemployment, sickness, disability, widowhood, old age or the lack of livelihood in circumstances beyond his control. (United Nations, 1948) Kemampuan perumahan menjadi agenda penting bagi majoriti negara di peringkat global. Keperluan manusia untuk mempunyai rumah sebagai keperluan asas yang perlu dipenuhi meletakkan isu kemampuan perumahan sentiada diberi tumpuan dan dibahaskan sepanjang tahun..

Single-stage ac–dc buck–boost converter for medium-voltage high-power applications

This study proposes three topologies based on single-stage three-phase ac-dc buck-boost converters suitable for medium-voltage high-power applications. The first two topologies are based on a dual three-phase buck-boost converter, with a three-winding phase-shifted transformer to achieve sinusoidal input currents, with relatively small ac filters. The limitation of these two topologies is the switching devices are exposed either to a high voltage beyond that tolerable by a single device. The third topology is based on three single-phase buck-boost converters; with their dc output terminals connected in series to generate high voltage. By using this approach, voltage stresses on the switching devices are greatly reduced, and sinusoidal input currents with nearly unity power factor is achieved over the entire operating range when using small ac filters. Analysis, PSCAD/EMTDC simulations and experimentation are used to assess the feasibility of the proposed topologies during normal operation. Major findings of this study are discussed and summarised as a comparison between the three topologies

Multilevel Converters: An Enabling Technology for High-Power Applications

| Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

Design Of A Single Phase Unity Power Factor Switch Mode Power Supply (SMPS) With Active Power Factor Correction [TK7881.15. N335 2008 f rb].

Pembekal kuasa mod pensuisan (SMPS) merupakan satu industri yang bernilai jutaan ringgit dan berkembang pesat dalam bidang elektronik kuasa. The Switch Mode Power Supplies (SMPS) are a multi-million dollar industry and continuesly growing industry within the field of power electronics

A Novel Three-Level Isolated AC-DC PFC Power Converter Topology with Reduced Number of Switches

The three-level isolated AC-DC power factor corrected (PFC) converter provides safe and more efficient power conversion. In comparison with two-level, three-level PFC converter has the advantages of low total harmonic distortion, low device voltage rating, low di/dt, better output performance, high power factor, and low switching losses at higher switching frequencies. The high frequency transformer (HFT) grants galvanic isolation, steps up or down secondary voltage, and limits damage in case of a fault current. The existing three-level converter based on solid-state transformer (SST) topologies convert ac power from the electrical grid to a dc load while maintaining at least the minimum requirements set by the international standards (i.e., high power factor and low total harmonic distortion). The SST topologies with the capability of controlling intermediate dc-bus and output voltage simultaneously require two full bridges at the primary and secondary side of the HFT. As the power level increases, the number of cascaded bridges increases accordingly, and the price associated with these semiconductor devices becomes highly expensive. As result, the demand of converting high power level led to emphasis on high performance and cost-effective power conversion topology. The aim of this dissertation is to develop a new low-cost and high-performance three-level isolated AC-DC (PFC) converter topology. The proposed topology replaces the conventional three-level inverter in the secondary side of the HFT by only two switches and four diodes while still maintaining the basic functionality of a three-level converter (i.e., regulating the output voltage, controlling the dc-bus voltage to be within desired limits). The advantages of this new topology are: (1) low conduction losses; (2) low-cost; (3) no need to consider the issue of the power backflow; (4) zero-voltage switching (ZVS) and zero-current switching (ZCS) at turn ON are inherently guaranteed without any extra control effort. Two isolated three-level AC-DC power converter topologies are developed and investigated through the dissertation. First topology is based on the neutral point clamping (NPC) converter, and the second topology composed of the T-type converter. Two scale-down prototypes rated at 900-W and 1kW, 200 V are built to test the overall performance of the proposed topologies. The first and second topologies exhibit 94.5 % and 95.8 % efficiency scaled at a nominal power, respectively. The secondary bridge (novel circuit) in both topologies, which consists of two switches and four diodes, has 99.34 % practical efficiency

Low Voltage Regulator Modules and Single Stage Front-end Converters

Evolution in microprocessor technology poses new challenges for supplying power to these devices. To meet demands for faster and more efficient data processing, modem microprocessors are being designed with lower voltage implementations. More devices will be packed on a single processor chip and the processors will operate at higher frequencies, exceeding 1GHz. New high-performance microprocessors may require from 40 to 80 watts of power for the CPU alone. Load current must be supplied with up to 30A/µs slew rate while keeping the output voltage within tight regulation and response time tolerances. Therefore, special power supplies and Voltage Regulator Modules (VRMs) are needed to provide lower voltage with higher current and fast response. In the part one (chapter 2,3,4) of this dissertation, several low-voltage high-current VRM technologies are proposed for future generation microprocessors and ICs. The developed VRMs with these new technologies have advantages over conventional ones in terms of efficiency, transient response and cost. In most cases, the VRMs draw currents from DC bus for which front-end converters are used as a DC source. As the use of AC/DC frond-end converters continues to increase, more distorted mains current is drawn from the line, resulting in lower power factor and high total harmonic distortion. As a branch of active Power factor correction (PFC) techniques, the single-stage technique receives particular attention because of its low cost implementation. Moreover, with continuously demands for even higher power density, switching mode power supply operating at high-frequency is required because at high switching frequency, the size and weight of circuit components can be remarkably reduced. To boost the switching frequency, the soft-switching technique was introduced to alleviate the switching losses. The part two (chapter 5,6) of the dissertation presents several topologies for this front-end application. The design considerations, simulation results and experimental verification are discussed

Dynamic modeling of pwm and single-switch single-stage power factor correction converters

The concept of averaging has been used extensively in the modeling of power electronic circuits to overcome their inherent time-variant nature. Among various methods, the PWM switch modeling approach is most widely accepted in the study of closed-loop stability and transient response because of its accuracy and simplicity. However, a non-ideal PWM switch model considering conduction losses is not available except for converters operating in continuous conduction mode (CCM) and under small ripple conditions. Modeling of conductor losses under large ripple conditions has not been reported in the open literature, especially when the converter operates in discontinuous conduction mode (DCM). In this dissertation, new models are developed to include conduction losses in the non-ideal PWM switch model under CCM and DCM conditions. The developed model is verified through two converter examples and the effect of conduction losses on the steady state and dynamic responses of the converter is also studied. Another major constraint of the PWM switch modeling approach is that it heavily relies on finding the three-terminal PWM switch. This requirement severely limits its application in modeling single-switch single-stage power factor correction (PFC) converters, where more complex topological structures and switching actions are often encountered. In this work, we developed a new modeling approach which extends the PWM switch concept by identifying the charging and discharging voltages applied to the inductors. The new method can be easily applied to derive large-signal models for a large group of PFC converters and the procedure is elaborated through a specific example. Finally, analytical results regarding harmonic contents and power factors of various PWM converters in PFC applications are also presented here

Resonance mode power supplies with power factor correction

There is an increasing need for AC-DC converters to draw a pure sinusoidal current at near unity power factor from the AC mains. Most conventional power factor correcting systems employ PWM techniques to overcome the poor power factor being presented to the mains. However, the need for smaller and lighter power processing equipment has motivated the use of higher internal conversion frequencies in the past. In this context, resonant converters are becoming a viable alternative to the conventional PWM controlled power supplies. The thesis presents the implementation of active power factor correction in power supplies, using resonance mode techniques. It reviews the PWM power factor correction circuit topologies previously used. The possibility of converting these PWM topologies to resonant mode versions is discussed with a critical assessment as to the suitability of the semiconductor switching devices available today for deployment in these resonant mode supplies. The thesis also provides an overview of the methods used to model active semiconductor devices. The computer modelling is done using the PSpice microcomputer simulation program. The modifications that are needed to the built in MOSFET model in PSpice, when modeling high frequency circuits is discussed. A new two transistor model which replicates the action of a OTO thyristor is also presented. The new model enables the designer to estimate the device parameters with ease by adopting a short calculation and graphical design procedure, based on the manufacturer's data sheets. The need for a converter with a high efficiency, larger power/weight ratio, high input power factor with reduced line current distortion and reduced cost has led to the development of a new resonant mode converter topology, for power processing. The converter presents a near resistive load to the mains thus ensuring a high input power factor, while providing a stabilised de voltage at the output with a small lOOHz ripple. The supply is therefore ideal for preregulation applications. A description of the modes of operation and the analysis of the power circuit are included in the thesis. The possibility of using the converter for low output voltage applications is also discussed. The design of a 300W, 80kHz prototype model of this circuit is presented in the thesis. The design of the isolation transformer and other magnetic components are described in detail. The selection of circuit components and the design and implementation of the variable frequency control loop are also discussed. An evaluation of the experimental and computer simulated results obtained from the prototype model are included in the presentation. The thesis further presents a zero-current switching quasi-resonant flyback circuit topology with power factor correction. The reasons for using this topology for off-line power conversion applications are discussed. The use of a cascoded combination of a bipolar power transistor and two power MOSFETs i~ the configuration has enabled the circuit to process moderate levels of power while simultaneously switching at high frequencies. This fulfils the fundamental precondition for miniaturisation. It also provides a well regulated DC output voltage with a very small ripple while maintaining a high input power factor. The circuit is therefore ideal for use in mobile applications. A preliminary design of the above circuit, its analysis using PSpice, the design of the control circuit, current limiting and overcurrent protection circuitry and the implementation of closed-loop control are all included in the thesis. The experimental results obtained from a bread board model is also presented with an evaluation of the circuit performance. The power factor correction circuit is finally installed in this supply and the overall converter performance is assessed