Polar Coordinate Voltage Space Vector Control of Induction Motor Using Voltage Source Three Phase PWC Inverter

As a vector control system, we already reported a system in which the amplitude and the frequency of the phase current were separately controlled by a current source inverter of which output current waveform was smooth. In this system, the stability of the speed control was greatly influenced by the transient angular slip frequency of the phase current. In this report, we present a vector control system in which the amplitude and the frequency of the phase voltage are separately controlled without current control circuit, using a pulse-width controlled voltage source inverter. In this system, too, it is proved that the stability of the speed control is greatly influenced by the transient angular slip frequency of the phase voltage. This transient angular slip frequency changes the phase angle of the stator voltage space vector to the rotor flux interlinkage correspondingly to the torque variation. And the torque transfer function of this control system is derived, then its validity is experimentally proved. And furthermore, it is clarified that the control circuit under constant rotor flux interlinkage is simpler than that under constant stator flux interlinkage. The here presented control system of which controlled variable is voltage, is expected to be inferior to the system of which controlled variable is current in accuracy of torque control but superior in speed of response.