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Space vector modulation techniques for improved stator flux trajectory in direct torque control of induction motor DOI:10.15199/48.2019.05.04

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In direct torque vector control (DTC) systems, voltage source inverter (VSI) is describe in discrete mode as a source of constant amplitude voltage sources with strictly controlled direction, time duration and limited sample frequency. The output vector voltage vector may take up to seven different states and is altered in precisely specified time only at the command of given controlling signal. Therefore, the VSI dynamic state is discrete both in time and quantity. The stator flux space vector is used as a fundamental value in designing the control circuits of induction machine (IM). In this paper, therefore, the basic characteristics of stator flux space vector will be analysed in such a control concept for two different types of space vector modulation (SVM) techniques one is full block space vector modulation and second is called pulse edge space vector modulation.Advantages of the trajectory The selection of the switch-on and switch-off states of the power switches (Fig.1) is carried out so that the error between the real value of and the reference (assigned) value of moves within the limits of as defined by the hysteresis band of the flux controller. However, the selection of the states of the power switches not only depends on the absolute error value but also on the rotation direction of vector . For this purpose, the stationary reference domain is divided into 6 (six) equal parts (zones). Each zone has its own carrier voltage space vector. Thus, for instance, the carrier vector of the ‘0’ zone is vector . For a positive rotation direction (clockwise) the subsequent two voltage space vectors, and switch on respectively, depending on whether the upper or lower limit of the hysteresis band has been reached. For a negative rotation direction (counter clockwise) the corresponding vectors or switch on depending on whether the upper or lower limit of the hysteresis control band has been reached. The stator f[...]

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