On the interharmonic components generated by adjustable speed drives

The interharmonic generation process is addressed with reference to high power adjustable speed drives based on double stage conversion systems using line commutated or pulse width modulated inverters. Reference is made to ideal supply conditions. Formulas to forecast the interharmonic frequencies due to the interaction between the rectifier and the inverter are developed and a proper symbolism is proposed to recognize the interharmonic origins. Comprehensive analyses are performed for both the considered adjustable speed drives in a wide range of output frequencies and with reference to supply system side, output side, and dc link.