Harmonic and interharmonic currents generated by the VSI-fed adjustable speed drive

The voltage source converter (VSI) fed adjustable speed drives (ASDs) frequently generates significant amount of harmonic and interharmonic currents into the supply system and may cause undesired effects on other power system components. The traditional SPWM harmonic analysis method only suitable for synchronous modulation model, this paper uses a new method, which is suitable for the asynchronous modulation model too. This method directly sets up a mathematical module of the carrier in one period which is independent on the parity and the periodicity of frequency-modulated wave. The harmonic and interharmonic currents of the VSI-fed ASD injected into the supply system are calculated. By means of the electromagnetic simulation software PSCAD/EMTDC, the harmonic and interharmonic principle of the supply side is analyzed and the validity of the analysis method is confirmed by the simulation results.