A NEW APPROACH TO ENHANCE POWER QUALITY FOR MEDIUM VOLTAGE AC DRIVES

A new approach to medium-voltage variable-frequency static ac drives o ffers improvements in power quality. Harmonic current injection into t he power lines is below the most severe requirements of IEEE Standard 519-1992, The power factor of this new type of drive exceeds 94% at fu ll load and is above 90% at 10% load. Motor voltage and current wavefo rms are improved so that torque pulsations are reduced, peak voltage s tress on motor insulation does not exceed peak input line voltage, and no zero sequence voltage is imposed, Drive efficiency exceeds 96%. Th is paper describes the new approach and some of the results achieved.