Induction Motor Parameter Estimation via State Observer
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Solution Overview
Problem
Existing systems for controlling induction motors lack real-time parameter estimation, particularly for rotor resistance, which is affected by temperature changes due to load variations, leading to degraded control performance in vector control applications.
Innovation Solution
An apparatus that includes a state estimator, integral controller, and calculating unit to estimate rotor and stator resistance in real-time, using d and q-axis currents and voltages in a synchronous reference frame, and updating the magnetic flux angle calculation to enhance vector control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If real-time parameter estimation is implemented, then vector control performance is improved, but device complexity increases
Solution Approach 1:
The patent implements a state observer that continuously estimates rotor resistance based on feedback from measured stator currents and voltages. The estimated resistance is fed back to the control system to compensate for temperature-induced parameter changes, thereby maintaining vector control performance without requiring additional physical sensors
Solution Approach 2:
The patent replaces physical temperature sensors and direct measurement methods with a mathematical state observer that estimates rotor resistance parameters through computational algorithms. This substitution of mechanical/physical measurement systems with computational models reduces device complexity while achieving the desired control performance
2Measurement precision
If rotor resistance changes due to temperature variation, then control accuracy deteriorates, but adding estimation mechanisms increases system complexity
Solution Approach 1:
The state observer utilizes existing measurements of stator currents and voltages that are already available in the vector control system to self-estimate the rotor resistance parameter. No additional sensors or external measurement devices are required, as the system uses its own operational data to compensate for parameter variations
Solution Approach 2:
The patent dynamically adjusts the rotor resistance parameter based on temperature-induced changes by continuously estimating the parameter through the state observer. The estimated resistance value replaces the nominal resistance in the control algorithm, allowing the system to adapt to parameter changes without adding physical complexity
Data Source
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Figure 3A~3B
AI summary
An apparatus for estimating a parameter of an induction motor is provided. The estimating apparatus receives an output from a current controller and d and q-axis currents in a synchronous reference frame applied to an induction motor, calculates an error of rotor resistance, and obtains a difference between the rotor resistance and nominal rotor resistance to calculate stator resistance therefrom.