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Solution Overview
Problem
Existing methods for driving synchronous motors with a single power converter face stability issues, particularly in the low-speed range due to errors in resistance, inductance, and induced voltage constants, and detection errors, leading to unstable operation.
Innovation Solution
A drive device comprising a power converter, current detectors, magnetic pole position identification units, a subtractor, magnetic flux current command determination and compensation units, and a pulsation component extraction unit, which adjusts the magnetic flux current command based on the angular difference between the synchronous motors to stabilize operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If one power converter is used to drive two synchronous motors, then cost is reduced, but operation stability deteriorates in the low-speed range
Solution Approach 1:
The control unit continuously monitors the angular difference between the two synchronous motors and adjusts the magnetic flux current command in real-time based on this feedback. This closed-loop control ensures stable operation by dynamically compensating for deviations, particularly in the low-speed range where stability issues occur.
Solution Approach 2:
The system dynamically adjusts the magnetic flux current command parameter based on the angular difference between motors. By changing this electrical parameter in response to operational conditions, the system maintains stability across different speed ranges while using a single power converter.
2Reliability
If magnetic flux current command is increased to stabilize operation, then operation stability improves, but signal-to-noise ratio deteriorates
Solution Approach 1:
The control system dynamically adjusts the magnetic flux current command based on real-time angular difference measurements rather than using a fixed high value. This dynamic approach maintains stability only when needed (when angular difference exceeds threshold) while preserving signal-to-noise ratio during normal operation.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A drive device (100) includes a power converter (2), a magnetic pole position identification unit (5a), a magnetic pole position identification unit (5b), a subtractor (8), and a current control unit (6). The power converter (2) supplies power to a main-side synchronous motor (1a) and a sub-side synchronous motor (1b) connected in parallel. The subtractor (8) obtains an angular difference (λ) using the magnetic pole position of the rotor of the main-side synchronous motor (1a) identified by the magnetic pole position identification unit (5a) and the magnetic pole position of the rotor of the sub-side synchronous motor (1b) identified by the magnetic pole position identification unit (5b). A magnetic flux current command compensation unit (10) adjusts the absolute value of a magnetic flux current command (id*) based on the angular difference (λ). The current control unit (6) controls the power converter (2) using a torque current command (iq*) and the magnetic flux current command (id*) with the absolute value adjusted by the magnetic flux current command compensation unit (10).