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

Voltage source PWM inverter for PMSM supply
• instate of diode rectifier will be use the active rectifier, which provided
controllable DC-link voltage.
• or used bigger capacitor in the DC-link side in order to increase possibility of
filtering.
Let us summarize, adding influence of non-linear VSI causes by:
• serious distortion in the inverter output voltage,
• distorted machine currents,
• torque pulsation,
Additionally, also causes motor instability due to the interaction between motor and the
PWM inverter, or the choice of the PWM strategy [25].
Based on simulated and experimental observation one can say that the dead time effect
is:
• more visible in low speed operation of the motor,
• may become significantly in drives where high switching frequency is required
for good dynamics performances.
In some applications such as sensor-less vector control, the inverter output voltages are
needed to calculate the rotor or stator flux vectors. Unfortunately, it is very difficult to
measure the output voltage and requires additional hardware. The most desirable
method to obtain the output voltage feedback signal is to use the reference voltages
instead. However, the relation between the output and reference voltage is nonlinear due
to the dead-time effect and voltage drop across power devices. Thus, unless the properly
dead-time and voltage drop compensation will be applied, the reference voltage can not
be used instead of the inverter output voltage. Several compensation method were
proposed to overcome this problem. One of them will be present bellow.
Compensation based on modification of reference voltage waveform [17]
The compensation process of dead time effect and voltage drop across power devices on
the inverter output voltage from is illustrated in Fig. 3.14.
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