PMSM Power Converter Magnetic Pole Position Storage
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Solution Overview
Problem
Permanent magnet synchronous motors face challenges in estimating the magnetic pole position during startup after shutdown, particularly when no magnetic pole position sensor is used, leading to increased tact time and potential control issues due to the need for repeated magnetic pole position detection, which is inefficient and undesirable in applications with frequent start-stop cycles.
Innovation Solution
A power conversion device and control method that allows for the storage of magnetic pole position estimation data in memory, enabling the motor to start using initial estimation data instead of detecting the pole position each time, reducing the need for repeated detection and optimizing system configuration based on specific application requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic pole position detection is performed each time the motor is restarted after shutdown, then control reliability is maintained, but tact time increases and system efficiency deteriorates
Solution Approach 1:
The magnetic pole position estimation data is stored in memory before shutdown occurs. When the motor restarts, this pre-stored data is immediately used for control, eliminating the need for time-consuming re-detection. This preliminary action resolves the contradiction by maintaining control reliability through data persistence while dramatically reducing tact time during restart operations.
Solution Approach 2:
Instead of performing the complex magnetic pole position detection process again after shutdown, the system creates a copy of the estimation data and stores it in memory. This copied data is then reused during restart, avoiding redundant detection operations and reducing the time loss while maintaining the reliability needed for accurate control.
2Measurement precision
If magnetic pole position sensor is installed, then magnetic pole position can be detected at any time, but device complexity and cost increase
Solution Approach 1:
The system uses its own operational data (current and voltage information during motor operation) to estimate and store the magnetic pole position internally. This self-service approach eliminates the need for external sensors while maintaining the capability to know the magnetic pole position, thereby reducing device complexity and cost without sacrificing measurement precision during operation and restart.
Solution Approach 2:
The control device acts as an intermediary, using mathematical estimation based on available electrical measurements to derive magnetic pole position information without requiring direct physical sensing. This intermediary calculation approach replaces complex sensor hardware with computational methods, reducing overall system complexity while maintaining the necessary measurement accuracy.
3Productivity
If magnetic pole position estimation data is stored in memory, then restart efficiency is improved, but information loss occurs when current and voltage become zero during shutdown
Solution Approach 1:
The system performs the magnetic pole position estimation and stores the resulting data in memory before shutdown occurs, when current and voltage information are still available. This preliminary capture of position data ensures that the information is preserved in non-volatile or maintained memory, preventing information loss during the zero-current shutdown state and enabling efficient restart without re-detection.
Data Source
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AI summary
A problem exists in the prior art wherein when operation of a permanent magnet synchronous motor is stopped, current and voltage become zero and information cannot be obtained, thereby causing magnetic pole position information that has been estimated up until that point to be lost and resulting in the magnetic pole position information being estimated each time that the permanent magnet synchronous motor is restarted. Provided is a power conversion device that performs variable speed control of a synchronous motor in which a permanent magnet is used, that is provided with a power conversion unit that converts direct current into alternating current, and wherein: a current detection circuit that detects current that flows through the synchronous motor, an estimation means that estimates the magnetic pole positions of the synchronous motor when starting the synchronous motor, and a memory that stores magnetic pole position estimation data that indicates the magnetic pole positions at the time the synchronous motor is stopped are provided; and said power conversion device is configured so as to comprise a selection means that selects either magnetic pole position estimation data that is stored in the memory or magnetic pole position estimation data that is obtained by the estimation means and a control unit that uses the magnetic pole position estimation data that is selected by the selection means to drive the synchronous motor.