Rotor Position Estimation Using DC Current Amplitude Correction
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Solution Overview
Problem
Existing rotor position estimation methods for rotating electrical machines face challenges in accuracy during magnetic saturation, requiring increased calculation loads and slow response times, especially when not using a rotating coordinate system for drive control.
Innovation Solution
A control device that includes a current detector, position estimator, and controller to extract position estimation currents from rotating electrical machine currents, using a DC component of high-frequency current amplitudes for accurate rotor position estimation without increasing calculation load, even under magnetic saturation conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If saliency-based position estimation is used to enable position sensorless control in zero-speed or low-speed range, then the rotor position can be estimated without position sensors, but the estimation accuracy deteriorates when magnetic saturation occurs due to significant difference between estimated and actual positions
Solution Approach 1:
The patent introduces a correction value as an intermediary element to bridge the gap between estimated and actual rotor positions. The correction value is calculated based on torque information and added to the initially estimated position to compensate for errors caused by magnetic saturation, thereby improving measurement precision without sacrificing the sensorless control capability
Solution Approach 2:
The patent implements a feedback mechanism where the estimated rotor position and torque information are used to calculate a correction value that is then applied to improve the position estimation. This closed-loop approach continuously refines the position estimate by feeding back the torque-related position error information
2Measurement precision
If correction methods based on torque information are applied to improve position estimation accuracy during magnetic saturation, then the estimation accuracy improves, but the calculation load increases
Solution Approach 1:
The patent changes the parameter used for correction from complex multi-variable calculations to a simplified approach based on torque information alone. By utilizing the torque command value or actual torque as the basis for calculating the correction value, the method reduces computational complexity while maintaining improved position estimation accuracy during magnetic saturation
3Measurement precision
If rotating coordinate voltage superposition scheme is used to perform position estimation, then position estimation can be performed, but the response speed is slow due to convergence calculations and rotating coordinate conversion
Solution Approach 1:
The patent extracts only the necessary position estimation function from the complex rotating coordinate system framework. By performing position estimation directly in the stationary coordinate system using simplified voltage superposition and current extraction methods, it eliminates the need for rotating coordinate conversion and convergence calculations, thereby significantly improving response speed while maintaining estimation capability
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
Improves rotor position estimation accuracy while preventing an increase in calculation load, enabling stable estimation during magnetic saturation without the need for rotating coordinate systems.
Implementation Method 1
Methods for position sensorless control of a rotating electrical machine mainly include methods of estimating the position of a rotating electrical machine using an induced voltage of the rotating electrical machine and methods of estimating the position of a rotating electrical machine using saliency
Data Source
AI summary
A control device includes: a current detector that detects rotating electrical machine currents flowing to the rotating electrical machine; a position estimator that estimates a rotor position of the rotating electrical machine based on the rotating electrical machine currents; a controller that calculates drive voltage commands based on the rotating electrical machine currents and information on the rotor position, adds position estimation voltage commands and the drive voltage commands to obtain rotating electrical machine voltage commands. The position estimator extracts position estimation currents included in the rotating electrical machine currents, the position estimation currents being changed according to the position estimation voltage commands, and estimates the rotor position of the rotating electrical machine using a DC component of amplitudes of the position estimation currents extracted, the DC component being not changed according to the rotor position.