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

Voltage source PWM inverter for PMSM supply
3.4 Summary
The general conclusions from this chapters can be summarized as follows:
‣ to supply the voltage source inverter can be used diode rectifier or active
rectifier with IGBT transistors,
‣ supplied PMSM machine from VSI do not required mechanical comutator. It is
thanks to electronic commutation. This overcome the problem with brushes and
periodical service,
‣ The voltage source inverter is non-linear power amplifier in respect to:
o dead time effect,
o voltage drop across the power devices,
o DC link voltage pulsation.
‣ Without appropriate dead-time and voltage drop compensation, the sensorless
operation in low speed range is not possible.
‣ The quality of DC link voltage has influence on proper operation of AC drive,
‣ Sinusoidal modulation technique (SPWM) guarantees the inverter output voltage
U
DC
amplitude from 0 until V. This correspond to changes modulation index
2
from 0-0.785.
‣ Modulation techniques with zero sequence signals not equal zero guarantees the
U
DC
inverter output voltage amplitude from 0 until V (it is 15% grater than
3
SPWM). This correspond to changes modulation index from 0-0.907.
‣ In this work the PWM modulator with zero sequence signal of triple harmonics
(SVPWM) will be used. Mainly because of simple calculation of zero vector
duration and placement.
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