A Five Level DTC Scheme for Dual Inverter-Fed Five Phase Open-End Winding Induction Motor Drives with Single DC Source

This paper presents a five level direct torque control scheme for dual inverter fed five phase induction motor drives with open end stator windings. The proposed DTC scheme utilizes only the large voltage vectors of the five phase voltage space vector structure of the individual inverters to achieve five level torque hysteresis band based control. The two inverters of the proposed system can be supplied from a common DC source without causing circulation of common mode current since the switching scheme eliminates common mode voltages from the windings. Different voltage levels required for achieving the multilevel DTC operation are created using the adjacent line voltages and non-adjacent line voltages of the two inverters. The proposed switching scheme can produce 90% higher winding voltages compared to that of a star connected topology with the same DC link voltage. In addition, since only the large vectors are used in this scheme, the DC bus utilization is further improved. These aspects of the proposed scheme results in reduction in the DC link voltage requirement for a given application. The proposed DTC scheme is experimentally verified on a laboratory prototype under steady state as well as transient operating conditions.