Salient-Pole PM Rotor Position Estimation 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, without the need for two-phase or three-phase current measurement sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If DC injection method is used to determine initial rotor position, then the method is simple to implement, but 180 degrees misalignment error occurs due to DC parking behavior in salient-pole machines
Solution Approach 1:
The patent applies preliminary action by performing signal injection tests before DC injection to predict the DC parking position. The controller estimates where the rotor will park after DC injection based on pre-test signal responses, then adjusts the initial position estimate accordingly to compensate for the expected 180-degree error.
Solution Approach 2:
The patent implements feedback by using the results of signal injection tests to refine the initial rotor position estimate. The controller measures the response to test signals, calculates the predicted DC parking position, and uses this information to correct the initial position determination, creating a closed-loop correction mechanism.
2Measurement precision
If AC injection methods are used to determine initial rotor position, then polarity detection can be achieved, but 180 degrees error still occurs and the method becomes more complex
Solution Approach 1:
The patent extracts only the essential polarity detection function from complex AC injection methods. Instead of implementing full AC injection sequences, the patent uses simplified signal injection tests that extract only the necessary information about magnetic flux axis orientation and DC parking behavior needed for accurate initial position estimation.
Solution Approach 2:
The patent performs preliminary signal injection tests to detect polarity and predict DC parking position before the actual DC injection occurs. This preliminary action allows the system to prepare the correct initial position estimate in advance, avoiding the need for complex real-time correction during motor startup.
3Measurement precision
If two-phase or three-phase current measurement sensors are used, then current measurement accuracy improves, but the cost and device complexity increase
Solution Approach 1:
The patent applies self-service by using the motor's own phase windings as measurement sensors. The controller measures currents directly in the motor phases without requiring external current measurement sensors, thereby reducing device complexity and cost while maintaining sufficient measurement accuracy for position estimation.
Solution Approach 2:
The patent makes the phase windings serve multiple functions: they act as both the motor's functional components and as measurement sensors for current detection. This multi-functionality eliminates the need for separate current measurement sensors, reducing system complexity while maintaining measurement capabilities.
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, reducing the need for additional current measurement sensors and addressing the issues of 180 degrees misalignment and DC parking behavior.
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
Data Source
AI summary
A 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 includes: 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 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 the initial angular position of a rotor of a permanent magnet electrical machine.