A space vector modulation based direct torque control scheme for a current source inverter fed induction motor drive

Abstract

Direct torque control (DTC) scheme is quite popular in a voltage source inverter fed induction motor (IM) drive. Considering a switching table based algorithm, the flux and torque are directly controlled by applied inverter voltage vectors. There is a direct relation between stator flux and applied inverter voltage vector, which is eventually the stator voltage vector. However, in a current source inverter (CSI) fed IM drive, there is no direct relation between the stator flux amplitude and the applied current vector. Further, filter capacitor in between the inverter and motor terminals decouples the motor from the CSI. Hence, it is quite difficult to realise a switching table based algorithm to control stator flux. This paper proposes a new scheme to control flux and torque directly. The torque angle is calculated based on the electromagnetic torque demand; the torque angle and the output of flux controller generate the reference current vector. The dc link current is decided by the magnitude of the reference current and the CSI is switched through space-vector pulse width modulation scheme based on the the position of the reference current vector. The whole scheme is simulated in MATLAB/Simulink platform. The results show torque and flux are controlled properly.