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

Control methods of PM Synchronous motor
The DTC has lesser parameter dependence and fast torque when compare with the
torque control via PWM current control.
Among the well-know advantages of the DTC scheme are the following:
• Simple control,
• Excellent torque dynamics,
• Absence of coordinate transformations,
• Absence of separate voltage modulation block,
• Absence of voltage decoupling circuits,
• There are no current control loops, hence, the current is not regulated directly,
• Stator flux vector and torque estimation is required.
Among the well-know disadvantages of the DTC scheme are the following:
• variable switching frequency (difficulties of LC input EMI filter design),
• high sampling time is required (fast microprocessor and A/D converter ),
• inverter switching frequency depending on: flux and torque hysteresis bands,
machine parameters, sampling frequency,
• violence of polarity consistency rules (huge voltage stress for IGBT transistor),
• current and torque distortion caused by sector changes,
• start and low speed operation problems,
• high sampling frequency needed for digital implementation of hysteresis
comparators,
• high noisy level,
• high current and torque ripple.
Many modifications of the basic switching table based direct torque control (ST-DTC)
scheme at improving starting, overload condition, very low speed operation, torque
ripple reduction, variable switching frequency functioning, and noise level attenuation
have been proposed during last decade.
In the last five years, many researcher have been carried out to try solve the above
mentioned problems of ST-DTC scheme. Therefore, the following solutions have been
developed in order to eliminated mentioned before problems:
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