Srivastava, Rajiv Kumar (1988) Software controlled delta PWM inverters. Masters thesis, Memorial University of Newfoundland.
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The family of delta modulators can be characterized as uniformly sampled zero hysteresis, bang-bang type of controllers. Such systems are widely used in communication and instrumentation applications for encoding band-limited analog signals into binary waveforms i.e. A/D conversion. The inherent V/f ratio control and low order harmonic attenuation of modulated output are some of the attractive features of delta modulation which can be employed in voltage control of inverters and rectifiers. -- Delta modulated voltage source inverters, implemented by analog means, have shown improved performance over conventional PWM inverters. However, software controlled delta modulated inverters require less complex control circuitry and offer easier control of system parameters. This thesis is the study of the performance of voltage source inverters using different types of delta modulation strategies. Continuous time variables of delta modulators transformed into discrete time domain are able to generate switching waveforms to control a single phase voltage source inverter. Three types of delta modulation strategics are investigated. The results obtained from their implementation are compared and a suitable choice of a modulation strategy for on-line inverter operation is investigated. -- The effect of filter coefficients, input signal amplitude, sampling rate, and tracking step (∆) on the modulator performance is presented. In order to study the harmonic behaviour of the inverter output, a Fourier analysis is carried out. The predicted performance results confirm the advantageous features of the delta modulation techniques. -- For experimental verification, a single phase bridge inverter and associate base drive circuits are built. Microprocessor-generated switching signals are applied to control the operation of the inverter. The inverter is tested with passive as well as dynamic loads and a comparison between various modulation techniques is presented. Implications for further research are discussed.
|Item Type:||Thesis (Masters)|
|Additional Information:||Bibliography: leaves 165-168.|
|Department(s):||Engineering and Applied Science, Faculty of|
|Library of Congress Subject Heading:||Pulse-duration modulation; Delta modulation; Electric inverters|
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