A new approach for the computation of harmonics and interharmonics produced by AC/DC/AC conversion systems with PWM inverters

The computation of harmonics and interharmonics produced by AC/DC/AC conversion systems with PWM inverters is considered, and a new approach is presented. Basically, a new inverter model is introduced that is based oil the modulation function theory and is able to take into account the voltage ripple at the inverter input terminals. A rectifier model that was previously proposed and the new inverter model are first used in the framework of a direct injection procedure and, then, in all iterative harmonic and interharmonic analysis. The proposed model call be applied successfully to adjustable speed drives for asychronous motors, achieving better modeling accuracy with respect to approaches based oil simplified inverter modeling. They also allow a sensible reduction of computational burden with respect to the time-domain models. For this reason, they constitute an attractive tool inside Monte Carlo simulations for probabilistic analyses of harmonic and interharmonic distortion. Numerical experiments demonstrate the good performance of the proposed models and the need to account for the presence of interharmonics for high-power PWM drives. Copyright (C) 2009 John Wiley & Sons, Ltd.