Magnetic Pole Position Estimation Using 90-Degree Voltage Superposition
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Solution Overview
Problem
The existing magnetic pole position estimating apparatus for electric motors can only update original reference values once in a three-cycle unit of the carrier, limiting its ability to estimate the magnetic pole position without affecting the voltage reference update cycle.
Innovation Solution
A controlling apparatus for an electric motor that includes a superposed component generator, an inverter, and a magnetic pole position estimator, which generates a superposed voltage reference shifted by 90 degrees and detects changes in currents to estimate the magnetic pole position without affecting the voltage reference update cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-frequency component is superimposed on a PWM signal to estimate magnetic pole position, then the magnetic pole position can be estimated, but the voltage reference for driving the electric motor can only be updated once in a three-cycle unit of the carrier
Solution Approach 1:
The patent divides the carrier cycle into three distinct intervals: the first interval (one cycle of carrier) is used for PWM signal generation with original reference values, while the second and third intervals (remaining two cycles) are used for superimposing high-frequency components for magnetic pole position estimation. This segmentation allows independent optimization of each function within the three-cycle unit, enabling both accurate position estimation and maintained voltage reference update frequency.
2Measurement precision
If the magnetic pole position estimation is performed using conventional methods, then the position can be detected, but it affects the cycle at which voltage reference is updated
Solution Approach 1:
The patent implements periodic action by alternating between PWM signal generation and high-frequency superposition in a regular three-cycle pattern. The superposed voltage reference is generated periodically at specific intervals (second and third intervals) without disrupting the overall update cycle. This periodic structure ensures that magnetic pole position estimation occurs at optimal intervals while maintaining the original voltage reference update timing for motor control.
Data Source
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AI summary
A controlling apparatus for an electric motor according to an embodiment includes a superposed component generator, an inverter, a current detector, and a magnetic pole position estimator. The superposed component generator generates, at a predetermined cycle, a superposed voltage reference of which vector is shifted by 90 degrees with respect to that of a superposed voltage reference previously generated, in a coordinate system that is set to a stator of the electric motor. The inverter outputs a driving voltage that is based on a driving voltage reference superposed with the superposed voltage reference to the electric motor. The current detector detects currents flowing into respective phases of the electric motor at the predetermined cycle, and outputs the detected currents. The magnetic pole position estimator detects the magnetic pole position of the electric motor based on an amount of change in the detected currents.