Auxiliary Supply Assisted Input Current Harmonic Reduction in 12-Pulse Thyristor Rectifiers

Three-phase thyristor rectifiers have been used in industries for obtaining a variable DC voltage, but they have a problem that they include large lower-order harmonics in the input currents. For high power applications a 12-pulse configuration is useful for reducing them, but it still includes the (12mplusmn1)
^th
(m: integer) harmonics. In order to further reduce the harmonics, this paper proposes to insert an auxiliary voltage supply (AVS) to the DC bus of a 12-pulse thyristor rectifier. Theoretical analysis is presented, and a control strategy of AVS voltage is proposed. Reduction in the current harmonics is verified by simulation and experimental results