Field Weakening Control for Permanent Magnet Motor Torque Stability
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Solution Overview
Problem
Conventional field weakening control methods for permanent magnet motors fail to stabilize motor operation when torque references exceed the limit torque, and do not account for variations in power supply voltage, frequency, and inductance, resulting in inadequate torque output.
Innovation Solution
A field weakening control apparatus that adjusts the phase angle limit value based on predetermined state quantities, allowing for stable operation and maximum torque output even when torque references exceed the limit torque, by varying the phase angle limit value in response to power supply voltage, frequency, and inductance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a torque reference specifying torque above the limit torque is input, then the motor can potentially output higher torque, but the motor becomes unstable and goes out of order in the weakened field region
Solution Approach 1:
The patent changes the parameter of phase angle limit value dynamically based on operating conditions (power supply voltage, frequency, inductance) to maintain motor stability while allowing torque reference to exceed limit torque. The control apparatus adjusts the phase angle limit value according to detected state quantities, enabling the motor to operate stably in the weakened field region even with high torque references.
2Force
If a fixed voltage phase limit value is used for control, then the control method is simple, but maximum torque cannot be output when power supply voltage, frequency, and inductance vary
Solution Approach 1:
The patent transitions from a static fixed voltage phase limit value to a dynamic phase angle limit value that changes with operating conditions. The control apparatus detects power supply voltage, frequency, and inductance variations, then adjusts the phase angle limit value accordingly, enabling maximum torque output across varying conditions while maintaining manageable control complexity through systematic adaptation.
3Adaptability or versatility
If the phase angle limit value is fixed, then the control apparatus is simple, but it cannot adapt to variations in power supply voltage, frequency, and inductance
Solution Approach 1:
The patent implements feedback control by detecting power supply voltage, frequency, and inductance variations, then using this information to adjust the phase angle limit value. The control apparatus continuously monitors operating conditions and adapts the phase angle limit accordingly, providing high adaptability to variations while maintaining reasonable apparatus complexity through feedback-based adjustment.
Data Source
AI summary
A motor control apparatus which controls an output voltage reference for an inverter driving a permanent magnet synchronous motor based on d-axis and q-axis current references, d-axis and q-axis current detected values, and a computed frequency value. When a torque reference specifying torque greater than maximum torque that the motor can output is input, a limit value for a phase angle that is a deviation between a rotation phase reference of control and a rotation phase value of the motor is varied depending on a quantity of the predetermined state.