Showing papers by "Ramesh Oruganti published in 1997"

Single phase power factor correction — A review

Abstract: This paper provides a comprehensive review of the past and recent developments in the area of single-phase power factor correction (PFC) techniques. The motivation for the research in this area, and the manifold directions into which the research has gained impetus, are clearly brought out. The various PFC techniques are broadly classified into (1) passive, (2) active, and (3) active-passive PFC techniques. The active PFC techniques, based on the output dynamics, are further classified into (1) conventional techniques which have slow output dynamics and (2) techniques with fast output dynamics. The critical issues within each PFC technique are discussed in detail. An extensive list of references is also provided at the end.

Analysis and design of power factor correction using half bridge boost topology

Abstract: A single-phase, high efficiency, and near-unity power factor half-bridge boost power converter circuit, which has been proposed earlier by other researchers, is presented with detailed analysis. Though this power converter is capable of operating under variable power factor, the focus of this paper is in achieving unity power factor operation only. The efficiency of this circuit is high because there is only one series semiconductor on-state voltage drop at any instant. The existence of an imbalance in the voltages of the two DC link capacitors, which was noted before, is confirmed here. The cause of the imbalance is analysed using appropriate models, and a control method to eliminate it is discussed in detail. Analysis and design considerations for the power circuit using the fixed band hysteresis current control technique are provided. The analytical results are verified through simulation using switched and averaged circuit models of the scheme and also through experimental work. At 90 V AC input and 300 W, 300 V output, the experimental prototype demonstrates an efficiency of 96% and a power factor of 0.998. This power converter, with its relatively high DC output voltage, is well suited for 110 V utility supply system. A circuit modification for universal input voltage range operation is also suggested.

A single phase two-switch buck type AC-DC converter topology with inductor voltage control

Abstract: A single-phase AC-DC buck-type converter using only two switches is studied in detail. The converter is derived from half-bridge boost AC-DC converter using the principle of duality of electrical networks. The converter can be used with various control techniques such as sine PWM and phase control. An inductor voltage control method, capable of fast and robust input current control, is adopted here. With this control the converter can be made to draw a near sinusoidal input current with any arbitrary power factor while the output voltage may be controlled smoothly from a maximum value to zero volts. The proposed converter is analysed in detail, and analytical plots and expressions useful to a design engineer, have been developed. An averaged circuit model of the converter has been developed to obtain the analytical results of some of the circuit variables. This model can also be used successfully for fast and efficient circuit simulation studies. Besides providing the experimental results, the merits and demerits of the converter are also brought out.

A single phase parallel power processing scheme with input-shunt power factor correction stage

Abstract: A single-phase parallel power processing scheme with input-paralleled power factor correction stage is proposed. The input current in the proposed scheme is nearly-sinusoidal with power factor close to unity. This scheme is very attractive for systems with two or more independent loads, each requiring an AC-DC power converter. An example of one such system is a personal computer (the monitor and the CPU units). For such a system, the proposed scheme is both cost effective and efficient than the popular two-stage cascaded scheme. The scheme is implemented using a half-bride boost PFC stage, and is analysed in detail. Analytical plots and expressions useful to a design engineer, have been developed. Switched and averaged model simulation results, and experimental results are also included. An efficiency of 93.78% at 90 V input, and a power factor of 0.999 were obtained experimentally. The possible circuit variations of the proposed scheme have also been identified.

Implementation of predicted (on-time) equal charge criterion control of a single phase boost AC-DC converter

Abstract: The implementation of a constant frequency PWM scheme for shaping the input current waveform in a single phase AC-DC boost power converter is presented in this paper. The method controls the switching devices of the power converter in such a way that the average of input current over a switching interval tracks the average of the sinusoidal reference current over the same interval. Simulation studies showed that the method gives satisfactory operation for different loads and variable power factors. Practical implementation of the control method was done on an IGBT power converter switching at 10 kHz using a 80386 processor based system. Issues in the practical implementation of the method are addressed in this paper. The experimental results showed that the proposed method is capable of stable, transient free operation at various conditions, loads and power factors. The excellent dynamic response of the system with the proposed control is also illustrated with experimental results.