Space vector based DTC scheme for a 3-level inverter realized by cascading two 2-level inverters

This paper proposes a space vector based direct torque control (SVDTC) scheme implemented on a three-level cascaded inverter. The cascaded inverter configuration is implemented by cascading two two-level inverters. The proposed space vector DTC scheme avoids look up Table for the selection of switching voltage vectors as used in the conventional DTC scheme. The space vector algorithm used in this three-level SVDTC scheme eliminates the sector identification procedure and uses a mapping technique to simplify three-level to a two-level modulation scheme. Switching vector timing durations are determined for two-level mode and finally the required switching vectors are obtained by reverse mapping technique. The proposed method is practically implemented on a 2-hp induction motor driven by cascaded three-level inverter and experimental results are exhibited to validate closed loop speed control capability of the scheme.