Variable Speed Drive Rotor Parameter Adjustment
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Solution Overview
Problem
Existing variable speed drives for electric induction motors face performance degradation due to errors in estimating rotor resistance and inductance, leading to increased current consumption, overheating, and torque oscillations, as these parameters fluctuate over time, particularly with temperature changes.
Innovation Solution
A method to adjust rotor resistance and inductance values in real-time using the integral term of the current loop, by calculating correction values from differences between torque and flux current references and measurements, and incorporating these adjustments into the motor model to refine control voltages applied to the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotor resistance and inductance values are estimated using preliminary identification or empirical equations, then the initial motor model can be established, but the parameters become inaccurate over time due to temperature changes and flux variations
Solution Approach 1:
The patent implements a feedback mechanism where the actual motor currents (torque current and flux current) are continuously measured and compared with reference values. The integral terms of these current deviations are used to dynamically correct the rotor resistance and inductance parameters, ensuring the motor model remains accurate despite temperature changes and operating condition variations.
Solution Approach 2:
The patent dynamically changes the rotor resistance and inductance parameters based on real-time operating conditions. By using the integral terms of current deviations as correction values, the parameters are continuously adjusted to reflect actual motor state, thereby maintaining model accuracy over time and across different temperature and flux conditions.
2Device complexity
If fixed rotor resistance and inductance values are used in the motor model, then the control system is simpler, but current consumption increases and torque oscillations occur due to parameter drift
Solution Approach 1:
The patent uses feedback from actual motor currents to continuously correct the rotor parameters. The integral terms of the differences between actual and reference currents provide correction values that are applied to the rotor resistance and inductance, eliminating parameter drift and its harmful effects without requiring complex external measurement systems.
Solution Approach 2:
The motor control system performs self-correction by using its own current measurements and the integral terms of current deviations to automatically adjust its internal parameter model. This self-service mechanism eliminates the need for external parameter measurement equipment while maintaining accurate control and preventing harmful oscillations and overheating.
3Measurement precision
If real-time parameter adjustment is implemented using integral terms of current deviations, then motor control accuracy is improved, but the computational complexity of the control system increases
Solution Approach 1:
The patent implements feedback by continuously measuring motor currents and using the integral terms of their deviations from reference values to correct parameters. This approach achieves high measurement precision for rotor resistance and inductance while keeping the computational complexity manageable, as it uses standard integral calculations rather than complex optimization algorithms.
Data Source
Figure 1~2
AI summary
The invention relates to a method for adjusting motor parameters in a speed variator intended for controlling an induction electric motor M. The method comprises a step of determining the deviations ΔID and ΔIQ between references and measurements of the flux currents and motor torque, a step of calculating a correction value ΔRR of the rotor resistance and a correction value ΔLR of the rotor inductance from the integral terms of the deviations ΔID and ΔIQ, a step of adjusting the values of the parameters of the motor model from ΔLR and ΔRR, a step of developing the control voltages UD and UQ to be applied to the motor M using said adjusted values of the motor parameters.