A Novel Torque Control in Constant Power Region for IPMSM Under Six-step Voltage Operation

What is it about?

To increase output torque in constant power region of IPMSM for EV/HEV applications, a novel torque control based on voltage phase angle control is proposed to provide more accurate torque for IPMSM. First, the mathematic model of IPMSM under six-step voltage operation is derived. Then, phasor diagram based on fundamental frequency and ideal condition is used to explain the relation among torque, power and voltage phase angle. Moreover, Maxwell 2D simulation for IPMSM shows the detailed phenomena including generated torque, phase current, and magnetic flux distribution for developing controllers. Hence, the proposed method using phase voltage advancing angle to yield torque, consists of a command feedforward controller to give fast dynamic response, a PI regulator, a high resolution voltage angle injection to reduce torque ripple and an efficiency-based torque estimator to enhance torque accuracy under six-step voltage operation. Finally, a DSP-based motor drive is built to verify the proposed method using a 6kW/47Nm/1200rpm IPMSM. The experimental results measured by torque transducer are derived to show that torque ripple is significantly reduced, torque accuracy is improved, and constant power control is achieved from 1800 rpm to 3600 rpm. These results therefore confirm the superior performance of the proposed control method.

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Why is it important?

Maxwell 2D simulation for IPMSM shows the detailed phenomena including generated torque, phase current, and magnetic flux distribution for developing controllers. Hence, the proposed method using phase voltage advancing angle to yield torque, consists of a command feedforward controller to give fast dynamic response, a PI regulator, a high resolution voltage angle injection to reduce torque ripple and an efficiency-based torque estimator to enhance torque accuracy under six-step voltage operation.

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