Sensorless Induction Motor Slip Frequency Correction
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Solution Overview
Problem
Existing sensorless induction motor control devices fail to accurately estimate slip frequency at high motor speeds, leading to errors in speed estimation and reduced motor output due to incorrect voltage command signals.
Innovation Solution
A sensorless induction motor control device with a slip frequency correction unit that adjusts the slip frequency estimation based on the ratio of actual to ideal voltage command signals, ensuring accurate speed estimation and improved motor output by comparing the ideal and actual voltage command values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If slip frequency is estimated using the equation ωs^=K×IQfb/IDfb, then the control device can operate without speed sensors, but the speed estimation accuracy deteriorates at high motor speeds
Solution Approach 1:
The patent implements feedback control by comparing the actual voltage command signal value with the ideal voltage command signal value, and using the difference to correct the slip frequency estimation. The correction amount is calculated based on this voltage difference and applied to adjust the slip frequency estimation, thereby improving speed estimation accuracy at high speeds while maintaining sensorless operation.
2Device complexity
If the slip frequency estimation is not corrected, then the device complexity remains low, but the motor output is reduced due to voltage command signal errors
Solution Approach 1:
The patent changes the parameter being controlled from direct speed estimation to voltage command signal comparison. By comparing actual and ideal voltage command signal values and using this information to adjust the slip frequency estimation, the system improves motor output without significantly increasing device complexity. The correction is applied through parameter adjustment rather than adding complex hardware or algorithms.
Data Source
AI summary
A sensorless induction motor control device with a function of correcting a slip frequency wherein a slip frequency estimation unit estimates the slip frequency from at least one kind of current flowing through the motor. A voltage command value calculation unit calculates a D-phase voltage command value and a Q-phase voltage command value which are used for controlling a voltage applied to the motor using a Q-phase current command value calculated based on a difference between a speed estimation value, which is calculated using an estimation value of the slip frequency, and an externally supplied speed command value. An ideal voltage command value determination unit determines an ideal voltage command value using the speed command value and the Q-phase current command value. An actual voltage command value calculation unit calculates an actual voltage command value using the D-phase voltage command value and the Q-phase voltage command value. and A slip frequency correction unit compares the ideal voltage command value with the actual voltage command value and changes the estimation value of the slip frequency to make it smaller if the actual voltage command value is smaller than the ideal voltage command value.