Motor Rotor Resistance Estimation for Temperature Control
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Solution Overview
Problem
Permanent magnet type electric motors in environmentally friendly vehicles face reduced driving force and fuel economy due to temperature-dependent magnetization, leading to inefficient torque control.
Innovation Solution
An apparatus and method for controlling temperature changes in induction motors by estimating rotor resistance in real-time using a DQ-axis voltage command value, synchronous angle estimation, and power conversion, with a rotor resistance estimator calculating values from magnetic flux models and adaptive models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If real-time rotor resistance estimation is implemented using dual magnetic flux models, then torque control performance is maintained under temperature variation, but device complexity increases
Solution Approach 1:
The patent introduces magnetic flux estimation as an intermediary variable to indirectly obtain rotor resistance information. By estimating magnetic flux through voltage and current models without directly measuring rotor resistance, the system maintains torque control performance while avoiding the complexity of direct rotor resistance measurement hardware
Solution Approach 2:
The patent implements a feedback mechanism where the estimated rotor resistance is continuously fed back to adjust the torque control parameters. The rotor resistance estimator uses the difference between voltage model and current model magnetic flux estimations to generate real-time resistance feedback, enabling adaptive torque control under temperature variation
2Measurement precision
If rotor resistance is estimated using voltage model and current model magnetic flux estimation error, then rotor temperature can be monitored accurately, but measurement precision requirements increase
Solution Approach 1:
The patent creates a virtual copy of the magnetic flux measurement through mathematical modeling. Instead of directly measuring the difficult-to-obtain magnetic flux, the system uses voltage and current measurements to calculate estimated magnetic flux values through equivalent circuit models, achieving accurate rotor temperature monitoring without direct magnetic flux sensors
Solution Approach 2:
The patent replaces physical magnetic flux measurement hardware with computational modeling. By substituting the mechanical/physical measurement system with mathematical voltage and current models, the system achieves rotor temperature monitoring while avoiding the technical difficulties of direct magnetic flux detection
Data Source
AI summary
An apparatus for controlling a temperature change in a motor may include a rotor resistance estimator calculating a rotor resistance estimation value of the motor utilizing a DQ-axis voltage command value and a coordinate conversion DQ-axis current value, a synchronous angle estimator estimating a synchronous angle utilizing the rotor resistance estimation value, a rotor angular velocity of the motor and a DQ-axis current command value, a coordinate converter creating the coordinate conversion DQ-axis current value utilizing the synchronous angle and a sensing current value, a current controller creating the DQ-axis voltage command value utilizing the DQ-axis current command value and the coordinate conversion DQ-axis current value, and a power conversion unit converting the power according to the DQ-axis voltage command value and supplying the converted power to the motor.