Vector control schemes for Tandem-converter fed induction motor drives

The tandem converter is an arrangement of two inverters connected in parallel: a high-power pulse-amplitude modulated current-source inverter and a low-power pulse-width modulated voltage-source inverter. In comparison with an equivalent single voltage-source inverter, this structure offers several advantages, significant reduction of switching losses in particular. Results of experiments with a tandem inverter, and those of computer simulations of induction motor drives with that converter, are presented. Three vector control schemes for such drives were investigated: a) rotor-flux orientation with a voltage-controlled tandem converter, b) rotor-flux orientation with a current-controlled tandem converter, and c) stator-flux orientation with a voltage-controlled tandem converter. Performance characteristics of the described control schemes are discussed.