Inverter Stabilizing Compensation for Motor Control
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Solution Overview
Problem
Large permanent magnet motors with high electrical time constants experience instability and increased current ripple at high speeds due to interference loop gain issues, making it difficult to achieve stable motor control with existing vector control methods.
Innovation Solution
An inverter device with a stabilizing compensation calculation unit that adjusts the d-axis voltage command to reduce current control gain at rotational frequencies, using a phase compensation signal to stabilize the q-axis current, thereby maintaining control stability across varying electrical time constants and calculation periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vector control is applied to large permanent magnet motors with high electrical time constants, then motor control is achieved, but instability and current ripple occur at high speeds due to increased loop gain
Solution Approach 1:
The control device preemptively counteracts the harmful effect of increased loop gain at high speeds by calculating a speed-dependent correction value and applying it to adjust the gain. This preliminary anti-action prevents instability and current ripple before they occur, allowing stable motor control across the entire speed range including high-speed operation
2Reliability
If the calculation period for vector control is shortened to suppress loop gain, then control stability improves, but control responsiveness deteriorates
Solution Approach 1:
The invention dynamically changes the d-axis current control gain parameter based on motor speed. By adjusting the gain to decrease at high speeds and maintain at low speeds, the system achieves stable control across all operating conditions without requiring a fixed short calculation period, thus maintaining both stability and responsiveness
3Device complexity
If the d-axis current control gain is kept constant, then control simplicity is maintained, but current ripple and torque deviation increase at high speeds
Solution Approach 1:
The control system transitions from a static constant gain approach to a dynamic speed-dependent gain. The d-axis current control gain is automatically adjusted according to motor speed, decreasing at high speeds to suppress current ripple and torque deviation while maintaining simplicity in the control architecture through automated adaptation
Data Source
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AI summary
An inverter device for controlling a permanent magnet motor includes: a voltage vector calculation unit that outputs a voltage command; a stabilizing compensation calculation unit that calculates a correction amount for reducing a current control gain at a rotational frequency component of the permanent magnet motor; a correction calculation unit that corrects the voltage command outputted from the voltage vector calculation unit based upon the correction amount calculated by the stabilizing compensation calculation unit; and a power conversion unit that converts DC power to AC power based upon the voltage command that has been corrected by the correction calculation unit, and outputs the AC power to the permanent magnet motor.