AbstractThe object of this dissertation is to show that communication principles may be usefully applied to pulse-width modulated inverters to increase their useable frequency range, without increasing the switching frequency of the power devices.
The prior-art techniques of reducing harmonic distortion in pulse-width-modulated inverters is investigated, and it is shown that such techniques are mainly applicable -to constant voltage/constant frequency inverters.
It is shown that the sampling process inherent in existing pulse-width-modulated inverters is natural sampling. The results of theoretical and experimental analysis shows that this sampling process is the cause or considerable unwanted harmonic distortion at low values of carrier frequency to modulating frequency ratio when operating in both the synchronous mode and asynchronos mode.
The concept of regular sampling which is common in communication engineering but which has not previously been used in power inverters, is applied to the pulse-width modulation process, and it is shown that such techniques eradicate I the many undesirable features introduced by natural sampling.
The construction of a practical thyristor pulse-width modulated inverter whose control circuits incorporate regular sampling techniques is described. A harmonic spectral analysis of the output voltage waveforms from the power inverter shows that the useable frequency range of the inverter is considerably increased by the application of regular sampling techniques to the control circuit, without increasing the switching frequency of the power devices.
|Date of Award