Synchronous Motor Current Control Near the Voltage Limit
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Solution Overview
Problem
Conventional synchronous machine control methods struggle with stable current control near the voltage limit, leading to oscillations in d-axis and q-axis currents due to interference between the dq axes.
Innovation Solution
A synchronous machine control device that includes a current command computation unit for generating current commands through proportional-integral control, a voltage vector computation unit for generating voltage commands, a voltage limitation unit that prioritizes limiting the coaxial voltage command over the orthogonal axis voltage command to prevent voltage exceeding the limit, and a correction amount calculation unit for adjusting current or magnetic flux commands based on voltage limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If voltage limitation is performed on the orthogonal axis voltage vector to prevent voltage command value from exceeding the voltage limit value, then voltage utilization rate is improved, but oscillation occurs in d-axis current and q-axis current due to interference component between dq axes
Solution Approach 1:
The voltage vector is segmented into two independent components: a coaxial voltage vector (215) that acts in the same direction as the voltage limit value, and an orthogonal axis voltage vector (213) that acts perpendicular to it. By separately controlling these two components, the patent applies voltage limitation only to the coaxial component while allowing the orthogonal component to remain unaffected, thereby preventing oscillation in d-axis and q-axis currents while still improving voltage utilization rate.
2Productivity
If high voltage up to near voltage limit value is used to improve voltage utilization rate, then productivity is improved, but stable current control cannot be performed near voltage limit
Solution Approach 1:
The control system dynamically adjusts the voltage vector by separately controlling its coaxial and orthogonal components. Near the voltage limit, the system maintains stable current control by limiting only the coaxial voltage component while preserving the orthogonal component, enabling the system to operate at high voltage utilization rates without sacrificing current control stability.
Data Source
AI summary
A synchronous machine control device drives and controls a synchronous machine, the synchronous machine control device including: a current command computation unit that calculates a difference between a current command value for the synchronous machine and an actual current flowing through the synchronous machine and generates a current command value by proportional-integral control; a voltage vector computation unit that generates a voltage command value including a coaxial voltage command value and an orthogonal axis voltage command value based on the current command value generated by the current command computation unit; a voltage limitation unit that limits the coaxial voltage command value in preference to the orthogonal axis voltage command value to prevent the voltage command value from exceeding a predetermined voltage limit value; and a correction amount calculation unit that calculates the amount of correction of a current command value for correcting the current command value based on limitation of voltage determined by the voltage limitation unit, the current command computation unit being configured to correct the current command value by the proportional-integral control based on the amount of correction of a current command value.