Speed estimation apparatus for AC motor, driving apparatus for AC motor, refrigerant compressor, and refrigeration cycle apparatus
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Solution Overview
Problem
Existing sensorless control methods for AC motors face challenges in accurately estimating high-frequency speed pulsation, leading to difficulties in suppressing vibrations and noise, especially when the estimation response is limited, and preadjustment is often required for effective control.
Innovation Solution
A speed estimation apparatus that includes a model deviation calculation unit, a first angular velocity estimation unit for low-frequency components, and a second angular velocity estimation unit for high-frequency components, which calculates and combines these estimates to accurately feed back the angular velocity, enhancing estimation accuracy and control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless control method using adaptive observer is used, then cost is reduced and reliability is improved, but high-frequency speed pulsation cannot be accurately estimated
Solution Approach 1:
The speed estimation is segmented into two parts: basic speed estimation using the adaptive observer and high-frequency pulsation estimation using a separate pulsation detection unit. This segmentation allows each unit to specialize in its respective frequency range, enabling accurate detection of high-frequency pulsations without compromising the reliability of the sensorless control system.
Solution Approach 2:
The invention merges the basic speed estimation from the adaptive observer with the high-frequency pulsation estimation from the pulsation detection unit. By combining these two estimation results, the system achieves both the reliability of sensorless control and the accuracy of high-frequency speed detection.
2Measurement precision
If position sensor or speed sensor is used, then speed estimation accuracy is improved, but apparatus cost increases
Solution Approach 1:
The invention replaces the mechanical sensor-based speed detection system with an electrical signal processing system. By using the pulsation detection unit that analyzes electrical signals from the motor windings, the system achieves sensor-level accuracy without the cost and complexity of physical sensors.
3Stability of the object's composition
If estimation response is limited, then system stability is maintained, but high-frequency speed pulsation cannot be detected
Solution Approach 1:
The invention introduces a dynamic pulsation detection unit that operates independently of the stable but slow adaptive observer. This dynamic unit can rapidly respond to high-frequency changes while the main control system maintains stability, effectively decoupling the response speed requirement from the stability requirement.
Data Source
AI summary
A speed estimation apparatus for an AC motor includes a model deviation calculation unit, first and second angular velocity estimation units, and an adder. The deviation calculation unit calculates a model deviation based on a voltage, a current, and an estimated angular velocity of the motor. The first angular velocity estimation unit calculates a first estimated angular velocity as a low-frequency component including a DC component of a real angular velocity based on the model deviation. The second angular velocity estimation unit calculates a second estimated angular velocity as a high-frequency component of a real angular velocity based on a specific high-frequency component of the model deviation. The adder adds the first and second estimated angular velocities together. An addition value of the first and second estimated angular velocities is fed back as the estimated angular velocity to the deviation calculation unit.