Sensorless Electric Compressor Control via Repetitive Speed Correction
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Solution Overview
Problem
Conventional control devices for electric compressors face challenges in accurately controlling motor rotation speed due to narrow frequency handling ranges, leading to estimation errors and complexity in handling multiple frequency components during sensorless operation.
Innovation Solution
A control device with a target rotation speed setting portion, estimated rotation speed calculation, drive command signal generation, repetitive control portion, and reset signal generation based on pressure detection to manage rotation speed differences and cycle switching, enabling successful control of motors with complex load fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a peak filter with a specific load fluctuation frequency is used to reduce rotation speed deviation, then oscillation of the compressor is reduced, but the frequency range that can be handled is narrow and estimation errors occur when frequency components outside this range are input
Solution Approach 1:
The invention segments the frequency handling by using multiple peak filters, each tuned to different load fluctuation frequencies. These filters process different frequency components of the rotation speed deviation separately, allowing the system to handle complex frequency compositions effectively while maintaining accuracy across a broader spectrum.
Solution Approach 2:
The invention merges the outputs of multiple peak filters with different frequency characteristics. By combining the filtered signals, the system achieves comprehensive frequency coverage and maintains high estimation accuracy across various operating conditions, resolving the limitation of narrow frequency handling range.
2Adaptability or versatility
If multiple peak filters with different handling frequencies are connected in parallel to handle complex frequency components, then the frequency handling range is expanded, but tuning becomes complicated and difficult
Solution Approach 1:
The invention creates a universal control structure where multiple peak filters follow a standardized configuration and signal flow pattern. This multi-functional approach allows the system to handle various frequency components using the same architectural framework, simplifying the overall tuning process despite the increased number of filters.
Solution Approach 2:
The invention leverages the periodic nature of compressor load fluctuations by designing peak filters with periodic frequency characteristics. This allows the system to effectively capture and process different frequency components of the periodic load variations without requiring complex adaptive tuning mechanisms.
3Reliability
If sensorless control is applied to avoid sensors and their associated problems, then device size and cost are reduced, but speed estimation characteristics are influenced and oscillation suppression becomes difficult
Solution Approach 1:
The invention implements feedback control by using the output of the peak filters to generate correction signals that are fed back to adjust the rotation speed command. This feedback mechanism enables effective oscillation suppression in sensorless control by continuously correcting estimation errors based on the filtered deviation signals, maintaining stability without requiring physical sensors.
Data Source
AI summary
A control device for an electric compressor, capable of successfully controlling a drive motor of the compressor in response to the load fluctuation having complicated frequency components even when the motor is controlled in a sensorless manner, is provided. The control device for an electric compressor includes: a repetitive control portion 5 to which a rotation speed difference between a target rotation speed of a motor which drives the compressor and the estimated rotation speed is input to perform a repetitive operation using the rotation speed difference of one preceding cycle of the compressor, thereby reducing the rotation speed difference; a pressure detecting portion 1 for the compressor; and a reset signal generation portion 4 calculating a timing of one rotation of the compressor by counting the number of predetermined parts of load fluctuations of the compressor based on the pressure value of the compressor, thereby outputting a reset signal to the repetitive control portion according to the timing.