Direct Torque Control of Five-Phase Induction Motor Drives With xy Current Regulation Under an Open-Phase Fault-Condition

Switching table-based direct torque control (DTC) for multiphase drives performs well but is drastically overshadowed by high harmonic contents of the stator currents caused by uncontrolled xy subspace. To address this issue, the concept of a virtual vector (VV) based lookup table has been reported to make the sub-harmonics zero (xy plane: 10k±3, k = 0, 1..) in the literature regularly. However, the developed VVs concept duty ratios are fixed. The fixed duty ratios have disadvantages and especially in the faulty conditions the subharmonic spaces are depending on the fundamental subspace (i
x
=-i
α
). In such conditions, making the sub-harmonics zero is a really big challenge. Taking this as a challenge and developed a dynamic duty-ratio-based DTC technique under the open-phase fault condition and implemented it on a five-phase induction motor drive. Noted that the proposed dynamic duty-ratio-based VVs will be applicable for other multiphase machines too. This has been achieved based on the xy voltage commands arising from the closed loop xy current controllers over a sampling period of time.