The power quality impact of cycloconverter control strategies

A cycloconverter is a power electronic device used to convert constant voltage constant frequency AC power to adjustable voltage adjustable frequency AC power without a DC link. Cycloconverters inject significant harmonics and nonstandard frequency components (i.e., noninteger multiples of the power frequency) into power systems. The impact of cycloconverters on power quality is studied, and the relationships between power quality indices and cycloconverter control strategies are developed. Control strategies are proposed to minimize the power quality impact of the cycloconverters. An innovative group frequency concept is introduced. This is a technique whereby many frequency components in the cycloconverter voltage and current spectra are collapsed into several group frequencies, and the power quality impact of the group frequencies is the same as that of the full spectrum of the cycloconverter signals. Some concepts are illustrated by simulation, and some by measurement at a twelve pulse cycloconverter load.