Asynchronous Motor Flux Observer Control for Low-Speed Stability
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Solution Overview
Problem
Existing control methods for asynchronous motors face stability and reliability issues, particularly at low speeds, due to variations in stator resistance caused by temperature and the presence of an unstable operating region.
Innovation Solution
An improved control arrangement and method utilizing a flux sensor unit, polyphase flux sensors, and a flux observer to measure and calculate airgap flux, stator current, and stator voltage, enabling precise estimation of flux and motor angular speed, which are then used to stabilize control of the asynchronous motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If speed sensorless control is used to simplify the system, then device complexity is reduced, but stability deteriorates at low speeds
Solution Approach 1:
The patent introduces a flux observer as an intermediary component that estimates rotor flux and speed without requiring physical sensors. This mediator processes stator current and voltage signals to derive rotor state information, enabling sensorless control while maintaining stability through accurate flux estimation algorithms that compensate for the lack of direct measurement
2Device complexity
If stator resistance variations due to temperature are not compensated, then device complexity is reduced, but reliability deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where the flux observer continuously monitors estimated flux and uses this information to adjust control parameters. The system feeds back rotor flux estimates and speed estimates to compensate for stator resistance variations, maintaining control reliability despite temperature-induced resistance changes without requiring explicit temperature sensors
3Measurement precision
If flux observation with multiple signal inputs is implemented, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The flux observer is designed as a multi-functional unit that simultaneously processes multiple signal inputs (stator currents, stator voltages) to perform multiple estimation tasks (rotor flux, rotor speed, stator resistance). This universal estimator consolidates multiple measurement functions into a single processing block, improving measurement precision while managing complexity through integrated signal processing
Data Source
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AI summary
The present invention relates to the field of electric drive devices and electric motors for industrial applications, and more particularly to an arrangement and a method for controlling an asynchronous motor and a frequency converter. The arrangement of the present invention for controlling an asynchronous motor (3) comprises an inverter unit (2) arranged to drive said asynchronous motor (3); a flux sensor unit (4) comprising polyphase flux sensor/sensors placed in the airgap of said asynchronous motor (3) arranged to measure the polyphase airgap flux ψag,a, ψag,b, ... ψag,m of the asynchronous motor (3); a flux observer (5); and polyphase current sensors (31); wherein said flux observer (5) is arranged to calculate a flux estimate ψ̂ utilizing a received airgap flux ψ‾agsvector signal in a αβ-reference frame, a received stator current iss vector signal in a αβ-reference frame, a received stator current is vector signal in a dq-reference frame and either one of a received/calculated stator voltage reference or a received stator voltage uss vector signal in a αβ-reference frame, and wherein said flux observer (5) is used in control of said asynchronous motor (3).