High power density adjustable speed drive topology with medium frequency transformer isolation

This paper presents a new adjustable speed drive (ASD) topology that employs medium frequency (MF) transformer isolation. The proposed system consists of a new 3-phase push-pull based AC to DC rectifier with a MF AC link employing only two active switches. A single 5-limb multi-winding MF transformer is employed for isolation. The secondary side of the transformer is connected in a zig-zag configuration and is fed to 3-phase diode rectifiers, realizing 12-pulse rectifier operation. The advantages of the proposed system include high power density due to MF transformer isolation, low active switch count, and a simple modulation scheme. Furthermore, zig-zag transformer connection helps to balance leakage inductance on the secondary side. A 690 V_LL, 100 HP design example, detailed analysis and extended simulation results are presented to validate the performance of the proposed approach.