Sensorless AC Motor Control Using Magnetic Alignment Signatures
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Solution Overview
Problem
Existing sensorless control methods for electric machines face limitations in achieving full torque capability and dynamic performance, especially at high-load levels due to magnetic saturation and phase errors, which restrict their application to low torque density and modest dynamic performance requirements.
Innovation Solution
A drive system that injects high frequency carrier signals to measure magnetic alignment signatures, allowing for sensorless control by tracking rotor position and velocity, and incorporates a special rotor structure like the 'D-ring' to enhance magnetic saliency, enabling control over a full operating range of speed and torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high frequency signal injection is used for sensorless control, then rotor position and velocity can be tracked at zero and near zero speed, but torque capability is reduced due to magnetic saturation at high-load levels
Solution Approach 1:
The patent applies preliminary action by injecting high frequency carrier signals before the main excitation to pre-establish the magnetic alignment information. This allows the system to determine rotor position and magnetic alignment in advance, enabling sensorless control at zero and near-zero speeds without compromising torque capability during main operation.
Solution Approach 2:
The patent uses periodic action by continuously injecting high frequency carrier signals at regular intervals to periodically update the magnetic alignment signatures. This periodic injection maintains accurate rotor position tracking throughout the operating range, enabling both zero-speed sensorless control and full torque capability through continuous refresh of alignment information.
2Adaptability or versatility
If magnetic alignment signature measurement is used, then sensorless control over full operating range is achieved, but system complexity increases due to high frequency signal injection requirements
Solution Approach 1:
The patent applies universality by designing the high frequency carrier signal injection system to serve multiple functions simultaneously: it enables sensorless control at zero and near-zero speeds, provides rotor position tracking across the full operating range, and determines magnetic alignment information. This multi-functionality reduces the need for separate systems for different operating conditions.
Solution Approach 2:
The patent applies self-service by using the motor's own windings and magnetic circuit to generate and detect the high frequency carrier signals. The motor structure itself serves as the sensing element, eliminating the need for external sensors or additional measurement apparatus, thereby reducing overall system complexity despite the sophisticated control algorithm.
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 achieves sensorless control with improved torque control and reliability, overcoming the limitations of magnetic saturation and phase errors, enabling full torque capability and dynamic performance across a wide range of operating conditions.
Implementation Method 1
A magnetic alignment signature of the AC electric machine is measured from a generated carrier response signal
Implementation Method 2
inject a carrier signal to generate a carrier response signal that has sensitivity to magnetic alignment information
Data Source
Figure 1A~1B
Figure 2~3
Figure 4A
AI summary
A system and method for position sensorless control of an AC electric machine is disclosed. A drive system for driving an AC electric machine provides a primary current excitation to drive the AC electric machine, the primary current excitation comprising a current vector having a magnitude and angle. The drive system injects a carrier signal to the AC electric machine that is superimposed onto the current vector, with the carrier signal being selected to generate a carrier response signal that has sensitivity to magnetic alignment information of the AC electric machine at its operating point. The drive system measures at least one magnetic alignment signature of the AC electric machine from the generated carrier response signal and controls an orientation of the current vector using the measured at least one magnetic alignment signature, so as to achieve a desired magnetic operation of the AC electric machine.