THD IMPROVEMENT OF VARIABLE FREQUENCY SINGLE PHASE INVERTERS

摘要

A variable frequency, variable amplitude inverter is needed for testing electrical instruments, for power quality and EMC tests. In variable frequency inverter, the LC filter is designed according to the highest output frequency. But when the inverter is used in the lower frequency band, some harmonics appear because of switching delay and deadtime effects. These harmonics are in low frequency band, and can not be removed by the output filter. In this paper the effect of varying switching frequency in order to improve the total harmonic distortion, is investigated.