Vector Controller Virtual Inductance Axis Error Estimation
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Solution Overview
Problem
In position sensor-less control of permanent magnet motors, setting errors in resistance lead to estimation errors in axis error, making it difficult to minimize current at the same torque, especially when a non-zero d-axis current is generated.
Innovation Solution
A high-efficiency vector controller is developed that uses a virtual inductance value calculated from the detected q-axis current to estimate axis errors and calculate output voltage, even when the commanded d-axis current is zero, allowing for effective torque control despite resistance setting errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If position sensor-less control is used to eliminate sensors, then device complexity is reduced, but measurement precision of axis error deteriorates due to resistance setting errors
Solution Approach 1:
The invention changes the parameter used for axis error estimation from resistance-based calculation to inductance-based calculation. By using the relationship between q-axis current and inductance, the system achieves accurate axis error estimation without being affected by resistance setting errors, thus maintaining measurement precision while using sensor-less control
Solution Approach 2:
The invention introduces inductance as an intermediary parameter to bridge the gap between current measurement and axis error estimation. Instead of directly using resistance (which has setting errors) to estimate axis error, the system uses inductance derived from q-axis current characteristics as an intermediate step, which provides more accurate estimation results
2Ease of operation
If d-axis current is set to zero to simplify control, then ease of operation is improved, but torque control precision deteriorates when resistance setting errors exist
Solution Approach 1:
The invention implements feedback by continuously monitoring q-axis current and using it to calculate inductance values. This feedback mechanism allows the system to detect and compensate for the effects of resistance setting errors, maintaining torque control precision while keeping the d-axis current command simple (zero or minimal)
3Ease of manufacture
If conventional torque control methods are used, then ease of manufacture is maintained, but loss of energy increases due to inability to minimize current
Solution Approach 1:
The invention changes the control parameter from resistance-based to inductance-based calculation, enabling accurate current minimization. By using inductance derived from q-axis current to estimate axis error and optimize torque control, the system minimizes motor current and reduces energy loss while maintaining ease of manufacture through software-based control adjustments
Data Source
AI summary
In a system in which current is detected in an inexpensive manner or in a system in which a position detector is omitted, the present invention provides a high-efficiency vector controller for a permanent magnet motor that can minimize current at the same torque even when there is setting error (R−R*) in resistance. Even when a current value commanded for the d-axis is set to zero, a virtual inductance value calculated from a detected q-axis current value is used for output voltage value calculation and phase error estimation calculation; so even if there is setting error (R−R*) in resistance, current can be minimized at the same torque and thereby the present invention can provide a high-efficiency vector controller for a permanent magnet motor.