AC/DC/AC high voltage traction drives with quasi-zero reactive power demand

A novel AC/DC/AC conversion structure has been developed, referring to single-phase AC (25 kV/50 Hz) traction systems using induction motor drives. High-voltage converters delivering multilevel voltage waveforms with lower harmonic content have been employed on both the line side and the motor side. High-performance techniques have been studied for controlling the whole system, assuring a quasi-unitary power factor and a low distorted line current. The control system was designed following VSS (variable structure system) principles, obtaining high-dynamics responses and insensitivity to parameter variations and disturbances. Simulation results confirm the validity of the methodologies proposed and of the analyses performed