Externally Excited Synchronous Machine Flux Reduction Factor Calibration
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Solution Overview
Problem
The calculation of the rotor-to-stator reduction factor in externally excited synchronous machines is often inaccurate due to the unavailability or inaccuracy of manufacturer-provided data, leading to errors in current model flux estimation and excitation control.
Innovation Solution
A method and apparatus for calculating the rotor-to-stator reduction factor using a set of measurements, including setting a stator flux linkage reference and adjusting rotor excitation current, without relying on manufacturer-specific data, to determine the reduction factor through equations (13) and (14).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reduction factor is calculated from short circuit measurements and zero-load measurements using manufacturer-provided data, then the calculation method is simple, but the accuracy deteriorates due to data unavailability or inaccuracy
Solution Approach 1:
The system performs self-measurement of the reduction factor by utilizing its own operational data (stator currents, rotor excitation current, and stator flux linkage) during normal operation. This eliminates dependency on external manufacturer-provided data and enables the system to determine its own parameters accurately through self-service measurement and calculation processes
Solution Approach 2:
The calculation method uses feedback from actual operational measurements of stator currents, rotor excitation current, and stator flux linkage to continuously determine and update the reduction factor. This feedback mechanism ensures accurate parameter determination based on real-time system state rather than relying on potentially inaccurate pre-provided data
2Reliability
If manufacturer-provided data is used for calculation, then the process is straightforward, but reliability deteriorates due to data unavailability
Solution Approach 1:
The system determines the reduction factor using its own operational measurements rather than external manufacturer data. This self-service approach ensures reliability by using data that is always available during normal operation, eliminating the reliability issue of missing or unavailable manufacturer-provided data
Solution Approach 2:
The calculation method uses operational data (stator currents, rotor excitation current, stator flux linkage) that are already measured for other control functions. This multi-functional use of existing measurements ensures the reduction factor calculation is reliable and does not require additional specialized measurements or data sources
Data Source
AI summary
An apparatus for a drive for an externally excited synchronous machine. The apparatus sets a value for a stator flux linkage reference so as to enable operation in a linear region of a d-axis magnetizing inductance without saturation. The apparatus causes the drive to drive the externally excited synchronous machine with a speed within a linear modulation range using said value. During the driving, the apparatus adjusts a rotor excitation current reference to determine a minimum-load value of a rotor excitation current and causes increasing or decreasing of the rotor excitation current until a stator current is within a pre-defined range. Then, the apparatus determines operating values for the stator and rotor excitation currents and calculates a rotor-to-stator reduction factor based on the minimum-load and operating values of the rotor excitation current, the operating value of the stator current and the value for the stator flux linkage reference.