Selective harmonic elimination inverter and its application in power plants

A kind of selective harmonic elimination inverter is designed and the number of its switching angles in every period is varied with output frequency. The memory mode of switching angles in the memorize is determined according to the request of VVVF (variable voltage variable frequency) and the variable voltage is made synchronous with the variable frequency by lock-on circuit for avoiding the appearance of voltage pinnacle in output waveform. The experimental results in power plant show that the designed inverter has obvious energy-saving effect, steady frequency transformation, the ability to eliminate various orders harmonic, the small amplitude of remnant harmonic and the small heat loss from electromotor.