Two-Quadrant Power Control for Large-Current, Low-Voltage Rectification with Reference to Aluminium Smelters

Abstract Large-current, low-voltage applications such as aluminium smelters use diode-saturable reactors or thyristor-based rectification to control the DC current. Transformer on-load tap-changers are also used to minimise the steady-state reactive power requirements. This paper describes a new double-group, two-quadrant thyristor-based concept suitable for high current, where several thyristor and insulated gate bipolar transistor bridges are paralleled. By using a combination of leading and lagging firing angles, high power-factor is maintained and supplying bridges via phase shifting transformers enables continuous high-pulse operation. The theory is verified by EMTDC simulation.