Direct torque control of open-end winding induction motor drive using the concept of imaginary switching times for marine propulsion systems

This paper proposes a control strategy for marine propulsion systems using the open-end winding configuration of induction motor. It uses the concept of imaginary switching times for space vector pulse width modulation (SVPWM) with direct torque control (DTC). The imaginary switching times greatly simplifies the algorithm. This method also eliminates the procedure for identifying the region for space voltage vector. Also, it does not require the sectors and angle identification of the voltage vector. Two independent two-level inverters feed power from both the ends of the three-phase stator windings. This applies a 3-level line voltage waveform to the machine. This reduces the torque ripple with improvement in current spectrum. In order to restrict the zero sequence currents, two isolated DC sources are considered. Simulation studies have been carried out for the proposed scheme. Experimental results have been presented to validate the viability of the scheme.