Direct Torque Controlled Space Vector Modulated Induction Motor Fed by a Z-source Inverter for Electric Vehicles

This paper proposes a new closed loop speed control of an induction motor fed by a high performance Z-source inverter (ZSI), the speed control is based on direct torque control space vector modulation (DTC-SVM) control strategy. The modified space vector modulation (MSVM) is used to insert the shoot-through state within the switching signals for the ZSI. A dual loop controller is designed to control the peak dc link voltage of the ZSI, where the peak dc-link voltage is estimated by measuring both the input and capacitor voltages. The peak dc link voltage control is designed based on small signal model using the bode diagram. Also, the parameters of the PI controllers in the DTC-SVM method are calculated based on the required dynamic specifications. The proposed speed control methods, with reduced DC input voltage compared with the standard adjustable speed drives (ASD), are able to change the motor speed from zero to the rated speed with rated load torque. The performance of the proposed speed control methods is verified by MATLAB simulation of a 15 kW induction motor fed by a high performance ZSI. The simulation results during start up, load disturbance and input voltage change are presented. The simulation results have verified the validity of the proposed DTC-SVM closed loop speed control method.

Publication year:2011

Keywords:Z-source inverter, Direct torque control, space vector modulation