Rotor Position Estimation with Harmonic Correction in Multi-Winding Motors
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Solution Overview
Problem
Conventional methods for estimating rotor position and speed in electrical machines with multiple winding sets wound to have a phase-shift between them often result in inaccurate estimations due to harmonic content in feedback signals, leading to control instability and reduced operational range.
Innovation Solution
A method that involves deriving preliminary rotor operational parameters from measured currents and reference voltages for each winding set, calculating a harmonic correction term based on these parameters from multiple winding sets, and then correcting the rotor operational parameters to remove or attenuate predefined harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional EMF-based observer methods are used to estimate rotor position and speed, then the estimation process is simple and does not require additional sensors, but the accuracy of estimation is reduced due to harmonic content in feedback signals
Solution Approach 1:
The estimation process is segmented into two distinct stages: first deriving preliminary rotor operational parameters from measured currents and reference voltages using conventional EMF-based observer methods, then calculating harmonic correction terms based on these preliminary parameters to eliminate harmonic effects. This segmentation allows each stage to focus on specific tasks, maintaining system simplicity while improving accuracy through the added correction stage.
Solution Approach 2:
The harmful harmonic content is extracted and identified as a separate component affecting the estimation accuracy. By calculating harmonic correction terms that specifically target these harmonics, the method isolates and removes the harmful effect from the overall estimation process, thereby improving measurement precision without fundamentally changing the conventional observer structure.
2Object-affected harmful factors
If digital filters are applied to attenuate harmonics in current and voltage signals, then harmonic content is reduced, but phase delay is introduced which creates extra errors in speed and position estimation
Solution Approach 1:
Instead of filtering the input signals before processing, the method performs preliminary derivation of rotor operational parameters using the raw measured currents and reference voltages. The harmonic correction is then applied as a subsequent action based on these preliminary parameters, avoiding the phase delay problem that would result from filtering the original signals.
Solution Approach 2:
The preliminary rotor operational parameters serve as an intermediary between the measured feedback signals and the final corrected estimates. By working with these intermediate parameters to calculate harmonic correction terms, the method avoids directly filtering the current and voltage signals, thereby eliminating the phase delay issue while still achieving harmonic attenuation.
3Adaptability or versatility
If multiple winding sets with phase-shift are used in the electrical machine, then the operational range and power capability are extended, but harmonic content in the feedback signals increases leading to estimation errors
Solution Approach 1:
The method utilizes feedback from multiple winding sets with their inherent phase-shifts to calculate harmonic correction terms. By feeding back the preliminary rotor operational parameters derived from each winding set and using them to compute corrections, the system leverages the multiple winding configurations to improve accuracy rather than being hindered by the increased harmonic content.
Solution Approach 2:
The approach changes the parameters used in estimation by introducing harmonic correction terms that account for the specific harmonic patterns generated by multiple phase-shifted winding sets. Instead of treating all harmonic content as noise to be filtered, the method adjusts the estimation parameters to compensate for the structured harmonic patterns inherent in multi-winding configurations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method improves the accuracy of rotor position and speed estimations by effectively removing or attenuating dominant harmonics, thereby enhancing control performance and avoiding the need for additional filtering.
Implementation Method 1
deriving, for each winding set, a preliminary rotor operational parameter based on a (e.g. measured) current and a (e.g. reference) voltage of the respective winding set
Data Source
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AI summary
It is described a method of estimating a rotor operational parameter (θ,ω) of an electrical machine (3) comprising multiple winding sets (15a,15b,15c, 17a,17b,17c) wound to have a phase-shift between winding sets, the rotor operational parameter comprising rotor position (θ) and/or rotor speed (ω), the method comprising: deriving, for each winding set (15, 17), a preliminary rotor operational parameter (39) based on a current (23) and a voltage (27) of the respective winding set (15); calculating for at least two winding sets (15, 17) and for at least one predefined harmonic (h), a rotor operational parameter harmonic correction term based on the preliminary rotor operational parameter (39,θ1,ω1; 41,θ2,ω2) of at least two winding sets (15, 17); calculating for at least one winding set (15, 17), a corrected rotor operational parameter (11, 13, 12, 14) based on the preliminary operational parameter (39, 41) of this winding set and the rotor operational parameter harmonic correction term of this winding set, wherein in particular the corrected rotor operational parameter has at least one predefined harmonic removed or at least attenuated.