Certain control strategies for three-phase semi-converters for the operation of self-excited induction generators

The application of certain firing angle control techniques such as Negative Firing Angle Control, Extinction Angle Control, and Symmetrical Angle Control has been studied for the first time, for the operation of three-phase semi-converters. The input and output voltage and current waveforms and the expressions for the performance quantities of the converter, in terms of the respective control angles α, β, and γ, have been analytically derived. These results have been confirmed in the simulation of the converter with these control schemes employing MATLAB software tools. The schemes were applied for the control of Self-Excited Induction Generators popularly employed in the renewable energy conversion systems. Illustrative examples of such generator-converter systems, studied both theoretically and experimentally, have been presented for different types of loading patterns that would be required in practical applications and relative merits of the schemes are discussed. To ensure compactness, reliability and flexibility as closed loop schemes, microcontroller based firing circuits have been developed.