Amina Hasan Abedin

Input switched single phase high performance bridgeless AC-DC Zeta converter

A new input-switched single-phase high performance bridgeless AC-DC Zeta converter (Inverse SEPIC) topology is proposed. Instead of using a single phase rectifier followed by a boost DC-DC converter, or using a bridge rectifier with two diodes and two switches, the converters input is chopped at high frequency during positive and negative cycles by a single bidirectional switch to get step-up/step-down AC-DC conversion. Total Harmonic Distortion (THD) of the input current of the proposed circuit with small input current filter is low. Input power factor and the efficiency of conversion of the circuit are high. The circuit exhibits such performance with variable loads at constant frequency switching. No additional control is required to achieve the advantages.

Input switched single phase buck and buck-boost AC-DC converter with improved power quality

Two new topologies of single-phase AC-DC converter using Buck and Buck-Boost conversion with low input current THD and high input power factor are proposed. Instead of using a single phase rectifier followed by a boost DC-DC converter, or using a bridge rectifier with two diodes and two switches, the rectifiers input is chopped at high frequency during positive and negative cycles by a single bi-directional switch to get step-up/step-down ac-dc conversion. Total Harmonic Distortion (THD) of the input current of the proposed circuit with small input current filter is low. Input power factor and the efficiency of conversion of the circuit are high. No additional control is required to achieve the advantages.

Boost and Buck topology based single phase AC-DC converters with low THD and high power factor

Two topologies of single-phase Buck and Boost AC-DC converters are presented. Instead of using a single phase rectifier followed by a boost dc-dc converter, or using a bridge rectifier with two diodes and two switches, the rectifiers input is chopped at high frequency during positive and negative cycles by a bi-directional switch in each of the Boost and Buck conversion mode to get step-up or step-down ac-dc conversion. Total Harmonic Distortion (THD) of the input current of the proposed circuits with small input current filter is low. Input power factor and the efficiency of conversion of the circuits are high. The circuits exhibit such performance with variable loads at constant frequency switching. No additional control is required to achieve the advantages.

True three-phase bidirectional switch based AC-AC Buck-Boost converter topology

A new three-phase true bidirectional switch is proposed in this paper. This switch consist of a unidirectional switch enclosed in two three phase diode bridges with bidirectional input and output terminals. A family of simple topologies of three-phase AC-AC converters using the true bidirectional switch is possible as direct extension of DC-DC converters having similar operating principle. Steady state analysis and simulation results are presented in this paper using the Buck-Boost topology as an example. Performance of the circuit has been found satisfactory with duty cycle variation. The proposed converter can be used for AC-AC line conditioning to overcome voltage sags, surges, and load fluctuations. Because the proposed converters employ only two active devices, they can reduce cost and complexity and improve system reliability.

A single phase buck-boost AC-AC converter with low input current THD and high input power factor

Two new topologies of Buck-Boost single-phase ac-ac conversion are proposed. In one of the circuits a bi-directional switch with a single buck-boost inductor is used, whereas, in the other circuit a bi-directional switch with two separate buck-boost inductors are used. Both the circuits operate in buck-boost mode separately for positive and negative cycle of the supply. As a result the input current remains almost in phase with the supply voltage without any additional sensors and control circuit. It runs in free running mode. The input current becomes almost sinusoidal by the use of small input filter. Input current THD is very low and the input power factor is very high. The converters like other switch mode converters have variable efficiency with change in duty cycle. High efficiency is possible within a range of duty cycle.

Three phase three switch modular Vienna, Boost and SEPIC rectifiers

Vienna and Modular three phase Boost power factor correction rectifiers are similar in working principle and performance. In this paper two rectifier schemes are presented as Vienna Rectifiers scheme-1 and scheme-2. A third three phase rectifier scheme, the three phase three switch modular SEPIC rectifier topology is also presented. The SEPIC topology has step-up/down voltage gain characteristic, whereas Vienna rectifier schemes has step-up voltage gain characteristic. The performance results of the proposed three phase three switch SEPIC rectifier are presented in this paper in tabular and graphical formats.

Magnetic resonance angiography- an advanced technique in MRI using flow imaging

Magnetic resonance angiography (MRA) produces images of flowing blood. The intensity in these images is proportional to the velocity of the flow. It produces an image, which distinguishes between static and flowing blood. There are three general types of MRA, time-of-flight, phase contrast angiography, and contrast enhanced angiography.

Three phase one switch modular-boost/vienna power factor corrected (PFC) rectifier

The power conversion circuit of a three phase Vienna or Modular-Boost switching power factor corrected (PFC) rectifier uses three controlled switches, eighteen diodes and two output split capacitors. Three PFC controller circuits are necessary for conversion circuits voltage regulation, power factor control and input current waveform improvement. The circuit has been modified to have fewer active and passive components in the power circuit. The input voltages and currents are sensed and conditioned to one voltage and one current signal for the feedback controller circuit. Reduction of controlled switches, diodes of the power circuit, sensors, isolation, base drive supply circuits makes overall operation of the circuit reliable. The proposed three phase boost PFC rectifier circuit is easy to design, fabricate, operate and maintain. It occupies less space and is lighter in weight. Disadvantages of unidirectional power flow and only step-up voltage gain characteristics of conventional three phase Vienna/Modular-Boost rectifiers remain in the proposed modified circuits.

A modular one-switch three-phase Single Ended Primary Inductor (SEPIC) rectifier

An input switch based modular Single Ended Primary Inductor (SEPIC) three phase AC-DC converter is proposed in this paper. The proposed rectifier has the advantage of step-up/down voltage gain with boost input stage. Input boost stage allows input current shaping accompanied by power factor correction. The topology will also provide possible capacitive isolation of input/output sides of the converter. The rectifier has minimum number of controlled switch, less number of diodes, fewer controller components and driver, isolators, sensors and heat sinks than other input switched three phase rectifiers. As a result, the proposed rectifier will be easy to operate, maintain, reliable in operation, light weight, compact and cost effective. The proposed three phase SEPIC rectifier is presented in this paper with its typical simulation and prototypes experimental results.

Diode-bridge enclosed one switch three-phase power factor corrected (PFC) Ĉuk rectifier

A new one-switch three phase power factor corrected (PFC) rectifier is presented in this paper. The proposed 3-phase ac-dc converter is based on Ĉuk topology. Proper feedback control of the circuit can maintain high power factor and low input current total harmonic distortion (THD). Use of minimum number of control switch in the proposed power conversion circuit reduces components, drivers drive isolation circuits, associated sensors and control circuits. The operation of the circuit is described by simulation and experimental results. The proposed 3-phase Ĉuk topology based rectifier is reliable in terms of operation, maintenance, control and efficiency of conversion. Boost input stage of the proposed circuit makes the circuit capable of being controlled like a single-phase boost PFC rectifier. Due to Ĉuk topology based power conversion the converter provides boost-buck ideal input/output voltage gain relationship.