Salient-Pole PM Rotor Position Detection Without Phase Sensors
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Solution Overview
Problem
Existing methods for determining the initial angular position of a rotor in salient-pole permanent magnet electrical machines are prone to 180 degrees misalignment and require two-phase or three-phase current measurement sensors, which are not always necessary or effective.
Innovation Solution
A method involving two signal injection steps: a first pulse test to determine the initial angle of the permanent magnet flux axis, followed by a DC injection to adjust the rotor position, and a second pulse test to determine the final angle of the permanent magnet flux axis, allowing for the calculation of the initial angular position without needing two-phase or three-phase current measurement sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC injection method is used to determine initial rotor position, then the permanent magnet flux axis aligns with the current direction in surface mounted permanent magnet motors, but the magnetic flux does not align with the DC current direction in salient-pole permanent magnet motors due to saliency effects
Solution Approach 1:
The patent changes the operational parameters by injecting AC signals at multiple frequencies and measuring the resulting current responses. By analyzing the amplitude and phase of the current signals at different frequencies, the method determines the initial rotor position without relying on DC injection alignment, thereby accommodating salient-pole motor characteristics while maintaining measurement accuracy.
2Adaptability or versatility
If AC injection methods are used to determine initial rotor position, then the method can be applied to various motor types, but 180 degrees error occurs due to the polarity of the permanent magnet flux
Solution Approach 1:
The patent implements a feedback mechanism where the measured current responses are analyzed to determine the polarity of the permanent magnet flux. By using the amplitude and phase information from AC signal injections and comparing the responses, the system identifies the correct polarity and eliminates the 180 degrees error, thereby maintaining both adaptability and measurement precision.
3Measurement precision
If two-phase or three-phase current measurement sensors are used to measure current in the direction of the pulse, then accurate current measurement is achieved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts only the necessary measurement information by injecting AC signals and measuring the current responses through existing single-phase or simplified sensors. By analyzing the amplitude and phase of the current signals at different frequencies, the method obtains the required position information without needing complex two-phase or three-phase current measurement sensor systems, thereby reducing device complexity while maintaining measurement precision.
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 effectively determines the initial angular position of the rotor with improved accuracy and eliminates the need for two-phase or three-phase current measurement sensors, providing a more elegant and effective solution compared to prior art.
Implementation Method 1
a first signal injection step is performed, in which first signal injection step an initial angle of a permanent magnet flux axis is determined; a DC injection is performed, in which DC injection a direct current is injected into an idle salient-pole permanent magnet electrical machine
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
The present invention relates to the field of electrical machines and methods and arrangements for controlling electrical machines, and more particularly to determining an initial angular position of a rotor of a salient-pole permanent magnet electrical machine. The method for determining an initial angular position of a rotor of a salient-pole permanent magnet electrical machine connected to a frequency converter comprises: performing a first signal injection step, in which first signal injection step an initial angle of the permanent magnet flux axis θd,axis,1 is determined; performing a DC injection (12) is performed, in which a direct current is injected into an idle permanent magnet electrical machine to a DC injection direction; performing a second signal injection step, in which second signal injection step an angle of the permanent magnet flux axis θd,axis,2 is determined; and determining (16) the initial angular position of a rotor of a permanent magnet electrical machine.