Three-Phase Machine Current Correction via Recursive Algorithm
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Solution Overview
Problem
Existing methods for controlling three-phase machines are limited in correcting dynamic measurement errors in phase currents, leading to torque ripples and inefficiencies, particularly due to the need for precise additional sensors and inability to account for changing error structures during operation.
Innovation Solution
A method using a recursive algorithm to calculate correction parameters for amplification and offset errors in real-time, based on measured phase currents, which are then used to determine corrected phase currents for improved regulation, allowing for continuous adaptation to changing measurement errors without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a further highly precise current sensor is used to correct amplification errors, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses the existing current sensors to measure and detect amplification errors in themselves. The control unit calculates correction factors based on measurements from the same sensors that are being corrected, eliminating the need for additional precise sensors. The system self-diagnoses and self-corrects its measurement errors.
Solution Approach 2:
The invention changes the parameters of the existing sensors by calculating and applying correction factors to their output signals. Instead of replacing sensors with more precise ones, the system modifies the electrical parameters (amplification factors) of the existing sensor signals through computational correction.
2Measurement precision
If filtering of intermediate variables is performed to determine correction factors, then measurement precision is improved, but the three-phase machine must be operated stationary over long distances, reducing productivity
Solution Approach 1:
The invention transitions from a static correction approach (requiring stationary operation for filtering) to a dynamic approach where correction factors are calculated in real-time during machine operation. The control unit continuously updates correction factors based on current measurements, allowing the system to adapt to changing conditions without requiring stationary periods.
Solution Approach 2:
The correction process operates continuously during machine operation rather than requiring intermittent stationary periods. The control unit constantly monitors phase currents and updates correction factors in real-time, ensuring continuous useful action both for correction and for machine productivity.
3Measurement precision
If existing correction methods are used, then amplification errors are corrected, but offset errors remain uncorrected, leading to torque ripples
Solution Approach 1:
The control unit performs multiple correction functions simultaneously - it corrects both amplification errors and offset errors using the same measurement and calculation mechanism. The system evaluates all three phase currents and determines correction factors that address multiple error types comprehensively, making the correction system universal rather than specialized for a single error type.
Data Source
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AI summary
Method and apparatus for correcting phase currents (iU, iV, iW) of a three-phase machine (1), wherein measurement values of the phase currents (ĩ U , ĩ V , ĩ W ), which measurement values are affected by gain errors and/or by offset errors, are detected and are used to control the phase currents (iU, iV, iW), characterized in that, during operation of the three-phase machine (1), correction parameters (α; αU, αV, αW, βU, ßV, ßW) for correcting the gain errors or offset errors are calculated from the measurement values of the phase currents ( ĩ U , ĩ V , ĩ W ), wherein corrected phase currents (i'U, i'V, i'W) are determined using the correction parameters (α; αU, αV, αW, βU, ßV, ßW) and said corrected phase currents are passed on to the control system for the phase currents (iU, iV, iW).