Improvement of power quality in VSI drives

The popular VSI (voltage source inverter) drives in use today are mostly PWM (pulse width modulated) drives. Harmonics produced by these drives cause heat losses, reduce the efficiency of the machine and also cause vibrations in the rotor. Active and passive filters are some of the methods to reduce the harmonics generated by these drives. A novel method is discussed which not only eliminates the 5^th harmonic but also any other negative sequence harmonics. This method, based on a reactor circuit, shows a reduction in harmonics and an improvement in the efficiency of the machine. The method can also reduce negative sequence harmonics produced by other nonlinear devices.