A PWM CSI-based vector controlled medium voltage AC drive with sinusoidal input and output waveforms

A vector controlled medium voltage AC motor drive is proposed in this paper which is based on a current source topology consisting of a PWM GTO current source inverter (CSI) as the output connected to the motor and a two-module PWM GTO current source rectifier (CSR) as the front end. The output inverter is operated with selective harmonic elimination (SHE) patterns with variable fundamental frequency and a maximum switching frequency of 300 Hz. The conventional direct vector control strategy for induction motors is adapted to incorporate the effect of the output capacitors of the CSI. The front end two-module PWM GTO CSR is operated with an SHE pattern eliminating the 11th and 13th harmonics and is connected to the AC mains through a three winding transformer which also eliminates the 5th, 7th, 17th, 19th harmonics. The regulation of the DC link current is achieved by phase shifting the SHE pattern of the rectifier modules. The paper includes the study and analysis of the front end topology, the input transformer, input harmonic characteristics, input power factor for various industrial loads, the inverter control strategy, simulation results and experiments on a 50 kVA system.