DTC of open-end winding induction motor drive using space vector modulation with reduced switching frequency

A new control strategy for reducing the switching frequency of direct torque controlled (DTC) induction motor with open-end winding configuration is proposed. Two independent two-level inverters are feeding both ends of the three-phase stator winding. In order to achieve the required voltage vector, one of the inverters is clamped to a particular voltage vector for a minimum of one sampling interval, while the other one is controlled using space vector PWM technique. This arrangement applies a 3-level line voltage waveform to the machine. Since this configuration is generally used in high power applications, the effective switching frequency of one of the inverters is reduced. Also, isolating the input DC source of the inverters can eliminate the flow of zero sequence current. Hence a significant reduction in size and improvement in overall efficiency is achieved. Simulation studies have been carried out for the proposed scheme and results are compared with the conventional space vector PWM-DTC by taking the equivalent 2-level inverter into account.