Speed estimating device for AC motor, driving device for AC motor, refrigerant compressor, and refrigeration cycle apparatus
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Solution Overview
Problem
Conventional speed estimation systems for AC motors, particularly in sensorless control, face limitations in accurately estimating high-frequency pulsations, leading to insufficient vibration reduction and noise issues due to inadequate response to high-frequency speed fluctuations.
Innovation Solution
A speed estimating device for AC motors that includes a model deviation computing unit, first and second angular velocity estimating units, a compensation phase computing unit, and an estimated angular velocity calculator, which computes and compensates for disturbance frequencies to enhance speed estimation accuracy at high frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional speed estimation control is used in sensorless control of AC motor, then the control system is simple and cost-effective, but the speed estimation response is insufficient at high frequency and cannot accurately estimate pulsation
Solution Approach 1:
The speed estimation system is divided into two independent parallel estimation paths: a conventional estimation unit for low-frequency components and a high-frequency estimation unit specifically designed for pulsation frequencies. Each unit processes the model deviation at its optimized frequency range, and the results are synthesized to achieve comprehensive speed estimation across the full frequency spectrum.
Solution Approach 2:
The high-frequency estimation unit dynamically adjusts its gain based on the detected pulsation frequency, allowing the system to adaptively optimize its response characteristics for different operating conditions and frequency ranges, thereby maintaining high estimation accuracy across varying speeds and load conditions.
2Object-affected harmful factors
If conventional speed estimation is used, then the system complexity is low, but the vibration reduction performance is insufficient due to inadequate high-frequency response
Solution Approach 1:
The control system is segmented into distinct functional units: conventional estimation for baseline speed control and high-frequency estimation specifically targeted at pulsation reduction. This segmentation allows each unit to be optimized for its specific function without requiring complete system redesign, thereby achieving vibration reduction with moderate complexity increase.
Solution Approach 2:
A compensation phase computing unit acts as an intermediary that processes the model deviation and generates phase compensation signals specifically for high-frequency pulsation components. This intermediary unit bridges the gap between the two estimation paths and enables effective vibration reduction through phase-aligned compensation.
3Measurement precision
If a single angular velocity estimating unit is used, then the device complexity is low, but the speed estimation accuracy at high frequency pulsation is insufficient
Solution Approach 1:
The estimation system is divided into two specialized units operating in parallel: one optimized for low-frequency speed estimation and another specifically designed for high-frequency pulsation estimation. Each unit processes signals independently at its optimal frequency range, and their outputs are combined to achieve accurate full-bandwidth speed estimation.
Solution Approach 2:
The results from the conventional estimation unit and the high-frequency estimation unit are merged through a compensation mechanism that combines both estimates. This merging process integrates the strengths of both estimation approaches, producing a final speed estimate that maintains accuracy across the entire frequency spectrum from low-speed operation to high-frequency pulsation.
Data Source
AI summary
A speed estimating device for an AC motor includes: a model deviation computing unit computing a model deviation based on a voltage, a current, and an estimated angular velocity of the AC motor; a first angular velocity estimating unit computing a first estimated angular velocity based on the model deviation; a second angular velocity estimating unit computing a second estimated angular velocity differing from the first estimated angular velocity in frequency, based on the model deviation; a compensation phase computing unit computing a compensation phase based on a disturbance frequency; and an estimated angular velocity calculator computing an estimated angular velocity of the AC motor based on the first estimated angular velocity and the second estimated angular velocity. Either one of the first estimated angular velocity and the second estimated angular velocity is computed based on the compensation phase.