TABLE OF CONTENTS A power electronic ac ac converter, in generic form, accepts electric power from one system and converts it for delivery to another ac system with waveforms of different amplitude, frequency, and phase. They may be singleor three-phase types depending on their power ratings. The ac ac converters employed to vary the rms voltage across the load at constant frequency are known as ac voltage controllers or ac regulators. The voltage control is accomplished either by (i) phase control under natural commutation using pairs of silicon controlled rectifiers (SCRs) or triacs or (ii) by on/off control under forced commutation/ self-commutation using fully controlled selfcommutated switches like gate turn-off thyristors (GTOs), power transistors, integrated gate bipolar transistor (IGBTs), MOS controlled thyristors (MCTs), integrated gate commutated thyristor (IGCTs), etc. The ac ac power converters in which ac power at one frequency is directly converted to ac power at another frequency without any intermediate dc conversion link (as in the case of inverters) are known as cycloconverters, the majority of which use naturally commutated SCRs for their operation when the maximum output frequency is limited to a fraction of the input frequency. With rapid advancements of fast-acting fully controlled switches, forced commutated cycloconverters, or recently developed matrix converters with bi-directional on/off control switches provide independent control of the magnitude and the frequency of the generated output voltage as well as sinusoidal modulation of output voltage...
