Date of Award


Document Type

Master Thesis

Degree Name

Master of Engineering


Electrical & Electronic Engineering

First Advisor

Dr. N. Barry


The trend towards digital and microprocessor based control of power electronic converters has increased the level of research into digital modulating techniques. This thesis examines the inherent digital nature of Binary Rate Modulation with particular attention concentrated on its suitability for dispatching power to three-phase loads. The circuit topology of a three-level inverter is also examined and its performance aspects are compared with those of the more conventional two-level inverter.

Integral cycle Binary Rate Modulation is applied to an ac voltage controller and this method of power dispatch, which displays an optimal ac cycle positioning property, is compared with Pulse Width Modulation dispatch. Harmonic analysis of loads using both techniques is described, revealing improvements in system performance when Binary Rate Modulation is used.

Speed control of a separately excited dc motor using Binary Rate Modulation is investigated and compared to Pulse Width Modulation control. It is shown that Binary Rate Modulation can be operated at a higher controller gain, effectively giving better disturbance rejection and faster performance in a closed-loop control system. Moreover, the method of producing Binary Rate Modulation waveforms is shown to be simple and comparable with that for Pulse Width Modulation in any computer system.

The application of Binary Rate Modulation to two-level and three-level bridge inverters is studied along with fundamental frequency switching which is the most suitable method of power dispatch for high power applications. The total harmonic distortion, and loss factors which give a good indication of the losses incurred by an induction motor are presented for Binary Rate Modulation, three-level, twelve-step and six-step operation as a means of comparison. Simulated and experimental results are also presented.

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