DC-Link Voltage Ripple Reduction via Position Error Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Non-ideal resolver signals due to manufacturing imperfections in electric machines induce periodic errors in position measurement, leading to oscillations in the DC-link voltage, which are exacerbated by reduced DC-link capacitance, causing power quality issues and potentially shortening the lifespan of capacitors.
Innovation Solution
A method to mitigate these oscillations by determining an estimated position waveform with error components, using coefficients to correct the position measurement, and increasing virtual resistance in the current regulator to reduce ripple in the DC-link voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If DC-link capacitance is reduced, then system efficiency is improved, but DC-link voltage oscillations are amplified
Solution Approach 1:
The patent implements a feedback mechanism by estimating position waveform errors and using this information to adjust control parameters. The system continuously monitors position measurement errors and feeds this information back to the current regulator to modify virtual resistance dynamically, thereby stabilizing DC-link voltage while maintaining reduced capacitance operation.
Solution Approach 2:
The patent changes the parameter of virtual resistance in the current regulator based on estimated position errors. By dynamically adjusting this parameter, the system compensates for the instability caused by reduced DC-link capacitance, allowing efficiency improvements without sacrificing voltage stability.
2Measurement precision
If position measurement precision is maintained, then control accuracy is improved, but manufacturing imperfections cause periodic errors
Solution Approach 1:
The patent extracts and isolates the periodic error components from the position measurement signal. By identifying and separating these error components caused by manufacturing imperfections, the system can compensate for them without affecting the overall measurement precision or requiring higher manufacturing standards.
Solution Approach 2:
The patent creates an estimated position waveform that copies the structure of the actual position signal but incorporates compensation for manufacturing errors. This estimated waveform serves as a corrected version that maintains the benefits of high measurement precision while accounting for resolver imperfections.
3Stability of the object's composition
If virtual resistance is increased, then DC-link ripple is reduced, but current regulator gain requirements increase
Solution Approach 1:
The patent makes the virtual resistance dynamic rather than fixed. By adjusting the virtual resistance based on estimated position errors and operating conditions, the system achieves DC-link stabilization without requiring excessively high fixed gain values, thereby managing current regulator complexity more effectively.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In an example embodiment, a method of controlling an electric machine includes obtaining an estimated position waveform, the estimated position waveform being based on a position of a rotor of the electric machine, the estimated position waveform having an error signal and an actual position waveform and determining a corrected position waveform based on the estimated position waveform. The determining the corrected position waveform of the rotor includes determining an estimated first coefficient and an estimated second coefficient and reducing at least one frequency component of the error signal using the estimated first coefficient and the estimated second coefficient to determine the corrected position waveform. The method further includes controlling the electric machine based on the corrected position waveform and reducing a ripple in a direct current (DC) link voltage based on the controlling.