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

Summary and closing conclusion
• position of PM flux has to be known prior to start up to achieve smooth
operation.
Therefore, for robust starting of PMSM without the temporary rotor reversal a simple
initialization algorithm has been used. This algorithm performs two tests: short and the
longer voltage pulses generated by the PWM inverter. The used speed estimation
algorithm is based on stator flux vector and torque angle estimation and does not
operate accurately in zero speed region. However, it allows robust start and closed
speed operation in the speed range above 10% of nominal speed. For application where
high performance operation around zero speed are required, the DTC-SVM drive with
motion sensor (encoder) is recommended. The effectiveness of DTC-SVM scheme with
and without motion sensor has been proved by simulation and experimental results
(Chapter 7).
Simulation study and experimental results have shown that from two variants of DTC-
SVM schemes the parallel structure is more flexible in torque and flux controller
design. Also, because of lack of the differentiation in the main control path (compare
Fig. 5.2 and Fig. 5.25), it is less sensitive to noise which inherently associates signal
processing in power electronic converters. Therefore, the parallel structure has been
selected for industrial manufacturing and implemented on digital signal processor
(DSP).
Thanks to direct torque and flux control structure the described control is suitable to
almost all – industrial applications including electrical vehicles (for example hybrid
cars).
Finally, it should be stressed that the developed system was brought into serial
production. Presented algorithm DTC-SVM has been used in new generation of inverter
drives produced by Polish company Power Electronic Manufacture – “TWERD”,
Toruń.
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