In this paper, a comparison is made between different

implementations of the three-level torque comparator

for a Direct Torque Control (DTC) based induction motor

drive. The DTC scheme controls stator flux and torque by

means of hysteresis comparators, respectively a two-level control

structure for the stator flux and a three-level comparator for

the electromagnetic torque. The standard three-level hysteresis

controller has a DC offset torque error. In this paper, an

additive implementation is investigated in order to remove this

DC offset error. The operational principles of the different

implementations are compared based on continuous and discrete

simulation results, which demonstrate the additional advantages

of the additive structure in a discrete implementation of the

control scheme.