Direct Torque Control with Space Vector Modulation (DTC-SVM) of ...

DSP implementation of DTC-SVM control
sampling time of microcontroller should be decrease. However there is hardware
limitation. The loaded program to microprocessor can not run faster.
Using the space vector modulation (SVM) based DTC much better results can be
obtained. Note, that in spite of lower switching frequency DTC-SVM guarantees less
current and torque ripple. This is mainly because contrary to hysteresis operation with
SVM operation, the inverter output voltage is unipolar (compare output voltage
waveform in Fig. 7.5a with Fig. 7.5b). This also reduces semiconductor device voltage
stress and instantaneous current reversal in DC link.
The presented experimental results (Fig. 7.6-7.9) are measured in the system with
measured speed taken to the feedback. These investigations have been performed to
show the behaviour of the DTC-SVM system without influence of the speed estimation.
In Fig. 7.6 and Fig. 7.7 steady state operation for different values of the mechanical
speed and load torque are shown.
Figure 7.6. Experimental steady state operation of PMSM controlled via DTC-SVM with the
encoder speed signal taken to the feedback ( Ω = 300rpm
, M = 0 ).
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From the top: 1) amplitude of stator flux (0.25Wb/div), 2) electromagnetic torque (10Nm/div),
3) line to line voltage (1000V/div), 4) stator phase current (10A/div).
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