Giri Venkataramanan

Design methodologies for soft switched inverters

A detailed design methodology is presented for soft switched inverters. The actively clamped resonant DC link inverter and the resonant pole inverter are taken as illustrative design examples with a detailed enumeration of component design rules, switching loss calculations, and system optimization. The soft-switched circuits are then compared with the conventional hard-switched voltage-sourced inverter under identical load conditions.<<ETX>>

Comparative evaluation of PWM AC-AC converters

Recently a new family of AC-AC power converters has been proposed for AC power conditioning. They are solid state functional equivalents of transformers with a continuously variable transformation ratio. Operating on the principle of pulse width modulated control using gate turn off devices like IGBTs, they have been shown to have significant performance advantages compared to older generation thyristor based phase controlled power converters. The family of proposed converters include buck, boost, buck-boost and Cuk power converters. This paper is aimed at presenting the design guidelines and the results of a comparative study of these power converters. Detailed design equations are provided along with a typical examples of design of various power converters for a power conditioning application.<<ETX>>

Advanced topologies and modulation strategies for multilevel inverters

Multilevel inverters have been attracting increasing attention in the past few years as power converters of choice in high voltage and high power applications. Various topologies to realize these inverters have been introduced and studied. Waveform synthesis methods for these inverters include staircase modulation, sine-triangle carrier modulation, space vector modulation, and other predictive methods. This paper presents the development of real-time voltage control techniques for multilevel inverters based on multilevel sigma delta modulators. The spectral performance of the output waveforms is investigated. Various design criteria, performance characteristics, comparison with existing modulation methods and other practical issues are discussed in detail in the paper.

Design of a versatile three-phase AC line conditioner

This paper describes the design of a line conditioner for three phase AC-AC power conditioning. It is based on a three phase PWM AC-AC buck-boost power converter. It has several advantages in terms of size, weight, efficiency and performance over state-of-the-art line conditioners. Design specifications and relationships are presented. Analytical formulae for determining the efficiency of the line conditioner are presented. A controller design which features fast transient response is developed. Operation of the line conditioner in the presence of voltage sags and surges, load addition and rejection is illustrated by means of simulation. Experimental results verifying the operation of the power circuit are also presented.

A direct AC-DC converter for battery chargers

The prospect of widespread introduction of electric vehicles has prompted the development of public and private access battery charging stations in California and elsewhere. Home charging stations generally aim at obtaining a unity power factor interface with the single phase utility power source to maximize power capacity utilization. The rectified AC source feeds power to an intermediate DC bus. The DC bus power is then converted into high frequency AC which is then coupled to the vehicle using an inductively coupled device. In this paper an alternative approach to the power conversion problem is presented. Operating limitations, design issues and simulation results are presented in the paper.

Characterization of capacitors for power circuit decoupling applications

Increase in switching speeds of power semiconductors have resulted in the need for decoupling capacitors to be placed across the DC bus, intimate to the semiconductor module in power converter circuits. These capacitors prevent overvoltages across the power semiconductor devices during switching transients. Moreover, they also reduce the high frequency content of the current flowing through the power circuit interconnection, thereby reducing electromagnetic interference. Various types of capacitors typically used for these applications include: metallized polypropylene film; foil and metallized polypropylene film; multilayer film; multilayer ceramic; and metallized polycarbonate. The parasitic properties of these capacitors including their ESR and ESL play an important role in proper application. The objective of this paper is to present a detailed characterization of the application and comparison of the various capacitors for DC bus decoupling. Characterization methodology, simulation results and design guidelines are presented in the paper.

Evaluation of inverter topology options for low inductance motors

Trends in modern motor designs require the power converter to satisfy stringent requirements. A few of the recently proposed quasi-resonant inverters have the capability to reach the performance levels required to drive these motors directly. A comparative evaluation of these inverter topologies is presented, with the conventional hard switched inverter as the base. All these inverters represent performance and size advantages compared to a conventional hard switched inverter. A preliminary reliability analysis reveals that the new topologies have somewhat smaller MTBF (mean time between failures) than the conventional hard switched inverter.<<ETX>>

A sliding mode observer for the induction motor

An observer is presented to estimate the magnetic flux components and speed of an induction motor based on stator voltage and current measurements alone. The observer is based on the principle of variable structure systems which immediately offers a number of advantages such as ensured stability, parameter insensitivity, noise rejection, etc. The principle of operation of a sliding mode observer is introduced in an intuitive manner using a simple first order system. Experimental results verifying the operation of the first order observer are presented. Then the sliding mode observer for the induction motor is discussed. Detailed simulation results verifying the operation under tuned and detuned conditions are presented. Practical realizations of the observer system based on robust implementation strategies are discussed.<<ETX>>