M. A. Choudhury

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 high performance three phase Buck-Boost controlled rectifier

Input current and power factor improvement of single and three-phase rectifiers by switch mode regulators are usually achieved by switching the output of rectifiers. The output switching makes input current high frequency switched, which is filtered by a small filter to get low input current THD at near unity power factor. In this paper a three phase Buck-Boost rectifier is proposed which is regulated at the input side by a three phase bi-directional switch. Direct input current switching ensures current displacement with input voltage always in phase. The number of diodes to achieve bi-directional input switching and output stage of the three-phase buck-Boost circuit increases. Comparison is made between proposed and conventional circuit under same loads and operating conditions. Results show that the proposed circuit has better performance for variable loads at constant frequency switching. The effect of increasing the number of semiconductor components have not been investigated completely.

Ćuk topology based single phase AC-DC converter wih low THD and high power factor

To topologies of single-phase Ćuk AC-DC converters 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 bi-directional switch in Ćuk conversion mode to get step-up/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.

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.

A three-phase boost AC-AC voltage converter

A two bi-directional switch based three-phase boost AC voltage regulator is presented in this paper. The operational principle of the proposed three-phase regulator is a direct consequence of using two three-phase bi-directional switches in the boost converter topology. The topology has reduced number of switches for a three-phase AC voltage regulator having output voltage regulation, input current shaping and power factor improvement capability. It provides opportunity for simple control technique to be adopted. In this paper output/input voltage feedback and boost inductor average current tracking method is used for controlling the regulator. Reduced number of switches allows simple control circuit, less switching loss, reliable operation and low cost. Steady state analysis and simulation results of close loop control of the proposed converter are presented in this paper. The average inductor current tracking control shows acceptable regulation of the converter output voltage. During sudden variation of load or input voltage the controller adjusts the duty cycle to recover to the desired output voltage. Experimental investigation of the converter without any feedback control is also described.

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.

Dead-Time Compensated Pulsewidth Modulator for a 3-Phase VSI Implemented with an AT89C52 Microcontroller

Modern microcontrollers are equipped with enhanced resources with built in huge flash program memory, increased RAM and EEPROM for data memory, timers, multi-channel ADCs and network controls. The enhanced on-chip resources make the microcontrollers a promising candidate for complex PWM implementations in embedded applications. In this paper a microcontroller based PWM implementation scheme is proposed that can produce high resolution PWM patterns for three phase inverters with dead-time compensation. An AT89C52 microcontroller computes the PWM pulse widths on carrier cycle basis based on the input frequency. The microcontroller send the pulse width information for the three phases to a memory minimized ROM lookup table, which is scanned by a binary counter to generate the real time PWM patterns. The on board timer of AT89C52 is utilized to generate programmed clock for the scanning binary counter. The ROM lookup table stores two types of PWM pattern for the same PWM duty in consecutive even and odd address locations. The even location stores the dead-time compensated PWM pattern for a leg for load current greater than zero. The immediate odd location contains the dead-time compensated pattern for current less than zero. A current feedback signal selects the appropriate PWM pattern for any duty and hence the resultant real time PWM pattern completely eliminates the dead-time effects resulting highly efficient PWM output.

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.