Effect of nonidealities on the performance of the 3-phase current source PWM converter

Usually, IGBTs in a current source converter are controlled by using a high switching frequency. This means that the filtered DC-link current and supply currents should not,include significant low order current harmonics. However, nonidealities like the switch overlap-time, the supply voltage unbalance or low order voltage harmonics in the supply voltages produce low order current harmonics into the DC-link and the supply currents. Especially, a 2nd, 6th and 12th harmonic appear in the DC-link current and a 3rd, 5th and 7th harmonic in the supply phase currents. These low order current harmonics are hardly attenuated by the filters which are tuned for the high order harmonics appearing around the switching frequency or it´s multiples. Thus, the low order current harmonics, for example, can be a source of resonance problems in a converter current control loops. The purpose of this paper is to show the amplitude levels of the low order current harmonics resulting from the nonidealities in the current source converter bridge. This will further help to understand the nonideal behavior of the converter