Power Conversion Device Drive Force Control Accuracy
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Solution Overview
Problem
The accuracy of drive force control in electric motors, particularly in unstable environments such as deep underground where heat generation affects motor performance, is compromised due to fluctuations in magnet magnetic flux and q-axis inductance, leading to deviations from drive force commands.
Innovation Solution
A power conversion device with processing circuitry that estimates magnet magnetic flux and q-axis inductance based on d-axis and q-axis magnetic fluxes, currents, and voltages, and corrects current commands to follow drive force commands, utilizing methods like ineffective force calculation and axis deviation estimation to improve torque estimation and control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional drive force control is used in unstable environments, then device complexity is reduced, but drive force control accuracy deteriorates due to fluctuations in magnet magnetic flux and q-axis inductance
Solution Approach 1:
The control device calculates ineffective force from voltage and current measurements, estimates angular error of the dq coordinate system based on this ineffective force, and uses this angular error to correct current commands. This feedback mechanism continuously adjusts control parameters based on actual motor state, maintaining drive force control accuracy despite fluctuations in magnet magnetic flux and q-axis inductance in unstable environments.
Solution Approach 2:
The invention replaces complex mechanical sensing and adjustment mechanisms with computational methods. Instead of using physical sensors to directly measure angular position and complex mechanical adjustment systems to compensate for inductance variations, the system uses mathematical calculations based on voltage and current measurements to estimate angular error and compute corrected current commands, achieving high precision control through software-based compensation.
2Measurement precision
If real-time estimation and correction methods are implemented, then drive force control accuracy is improved, but calculation complexity increases
Solution Approach 1:
The invention introduces ineffective force as an intermediary parameter that simplifies the estimation process. By calculating ineffective force from readily available voltage and current measurements, the system creates a intermediate value that directly reflects angular error without requiring direct measurement of magnetic flux or inductance. This intermediary approach reduces calculation complexity while maintaining estimation accuracy.
3Measurement precision
If current commands are corrected based on angular error estimation, then drive force following accuracy is improved, but response time may be affected
Solution Approach 1:
The control device continuously calculates ineffective force and estimates angular error in real-time during motor operation, maintaining continuous correction of current commands. This continuous action ensures that drive force following accuracy is maintained without interruption or delay, as the estimation and correction process operates continuously alongside motor operation rather than in discrete steps.
Data Source
AI summary
A power conversion device includes processing circuitry that estimates a magnet magnetic flux of an electric motor based on a d-axis magnetic flux generated in the electric motor, a d-axis inductance of the electric motor, and a d-axis current flowing in the electric motor, estimates a q-axis inductance of the electric motor based on a q-axis magnetic flux generated in the electric motor and a q-axis current flowing in the electric motor, estimates a drive force of the electric motor based on the magnet magnetic flux and the q-axis inductance, and corrects a current command such that the drive force follows a drive force command.