Aiming at the drawbacks of insufficient torque output of field-weakening control strategy in traditional direct torque control method
a maximum torque operation scheme is proposed by establishing voltage limit equation and current limit equation. Voltage limit area is combined with current limit area for maximum torque output consideration. The reference current vector and torque expression are calculated in field-weakening region one. Then voltage limit equation is combined with torque expression to get the maximum torque output in field-weakening region two. Theoretical analysis demonstrates that the new method can replace the traditional direct torque control scheme on speed regulation range in the whole field-weakening region. Compared with traditional direct torque control scheme in field-weakening region
the proposed method can improve torque margin by 21% under the same condition
and the new strategy is verified to be powerful for induction motor drive electric vehicles with lower energy from battery.
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references
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