Rotary Machine Angle Estimation Under Magnetic Saturation
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Solution Overview
Problem
Existing control systems for three-phase motors, particularly those with salient structures, face challenges in accurately estimating the rotation angle due to magnetic saturation, which affects the inductance distribution and makes it difficult to properly calculate the rotor's rotation angle, especially under high output torque conditions.
Innovation Solution
A control system that superimposes high-frequency signals with specific phases and periods onto the input signal of a multiphase rotary electric machine, using amplitude detection and correction mechanisms to determine the rotation angle, and accounts for saturation levels to maintain accurate estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high output torque is generated in a three-phase motor with salient structure, then the motor power increases, but magnetic saturation occurs causing inductance distribution to change and rotation angle estimation accuracy deteriorates
Solution Approach 1:
The invention changes the parameter of high-frequency signal amplitude dynamically. By adjusting the amplitude of the superimposed high-frequency signal based on operating conditions, the system maintains accurate rotation angle estimation even when magnetic saturation alters the motor's inductance characteristics. This parameter adaptation allows the estimation algorithm to compensate for saturation effects.
Solution Approach 2:
The invention implements feedback by detecting the actual amplitude of the high-frequency signal after it passes through the motor, comparing it with expected values, and using this information to correct the rotation angle estimation. The feedback mechanism enables the system to adapt to changing inductance distribution caused by magnetic saturation and maintain estimation accuracy.
2Power
If magnetic saturation occurs in a three-phase motor, then the inductance in d-axis direction becomes substantially equal to that in q-axis direction, but this makes it difficult to properly calculate the rotation angle of the rotor
Solution Approach 1:
The invention introduces a high-frequency signal as an intermediary carrier to extract rotation angle information. By superimposing this external high-frequency signal on the motor phases and detecting its response, the system can determine rotor position even when the natural back-EMF or current-based methods fail due to magnetic saturation eliminating the salient structure characteristics.
Solution Approach 2:
The invention uses periodic high-frequency signals superimposed on the motor phases to continuously probe the motor's inductance characteristics. This periodic excitation allows the system to track rotation angle in real-time, compensating for the loss of position information that occurs during magnetic saturation when the d-axis and q-axis inductances become equal.
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
The system effectively corrects for differences in amplitude and phase, ensuring accurate determination of the rotor's rotation angle even under conditions of magnetic saturation, enhancing the precision and reliability of rotation angle estimation.
Implementation Method 1
An output of a multiphase rotary electric machine is controlled based on an input signal thereto. A superimposing unit superimposes a first frequency signal on the input signal to the multiphase rotary electric machine
Data Source
AI summary
In a system for controlling rotation of a rotor of a multiphase rotary electric machine in relation to a stator thereof, a superimposing unit superimposes a first frequency signal on the input signal to the multiphase rotary electric machine. The first frequency signal has a first phase and a first period, and the first period is different from a period of rotation of the rotor. An amplitude detector detects an amplitude of a second frequency signal. The second frequency signal is actually propagated in the multiphase rotary electric machine with a second phase based on the superimposed first frequency signal. A rotation angle determiner determines a rotation angle of the rotor so as to eliminate a difference between the detected amplitude of the second frequency signal and a predetermined target amplitude thereof.