Multi-phase Machine Fault Detection via Harmonic Control Release
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Solution Overview
Problem
Existing methods for fault detection in multi-phase electrical machines, such as Fourier transforms and Vector Space Decomposition, are either computationally intensive or require significant faults to be detected, and do not effectively control harmonics during analysis.
Innovation Solution
A method using Vector Space Decomposition (VSD) to control multi-phase electrical machines by releasing harmonic control while maintaining fundamental current control, allowing for harmonic decomposition and fault detection based on current signatures, and subsequently re-establishing harmonic control to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Fourier transform is used for fault detection, then fault detection capability is provided, but computational complexity and processing time increase significantly
Solution Approach 1:
The patent extracts only the necessary frequency components (positive and negative sequence components) from the current signal using simplified transformation methods, rather than performing a complete Fourier transform. This extraction approach provides sufficient fault detection capability while significantly reducing computational complexity by focusing only on the relevant spectral information.
2Device complexity
If Vector Space Decomposition is used for fault detection, then computational load is reduced, but only very significant faults can be detected
Solution Approach 1:
The patent segments the current signal into distinct sequence components (positive sequence, negative sequence, and harmonic components) using VSD. By analyzing each component separately and comparing their magnitudes and characteristics, the method achieves enhanced sensitivity to subtle faults while maintaining low computational load. The segmentation allows detection of small imbalances that would be masked in a complete signal analysis.
3Productivity
If harmonic control is maintained during operation, then machine performance is optimized, but fault detection sensitivity to harmonic-related faults is reduced
Solution Approach 1:
The patent implements periodic switching between normal control mode (with harmonic suppression) and diagnostic mode (with harmonic control released). During diagnostic intervals, harmonic control is temporarily released to allow fault detection, then restored to maintain performance. This periodic action enables both high machine performance during operation and sensitive fault detection during diagnostic windows, resolving the contradiction between the two requirements.
4Measurement precision
If harmonic control is released for fault detection, then fault detection accuracy improves, but harmonic losses increase during analysis
Solution Approach 1:
The patent uses periodic action to release harmonic control only during brief diagnostic intervals rather than continuously. This allows accurate fault detection when harmonics are present, while limiting energy losses to short periods. The majority of operation time maintains harmonic control for efficient performance, making the temporary losses acceptable for achieving high detection accuracy.
Solution Approach 2:
The patent performs preliminary assessment of fault conditions by analyzing existing harmonic content before fully releasing harmonic control. This preliminary action allows the system to detect obvious faults without incurring full harmonic losses, and only releases control completely when necessary, minimizing energy waste while maintaining detection capability.
Data Source
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AI summary
A method of controlling a multi-phase electrical machine by means of a power converter, wherein the method comprises: a) controlling the electrical machine by utilising vector space decomposition, VSD, wherein the controlling involves releasing control of the current of a harmonic while maintaining control of the current of the fundamental, b) measuring phase currents of the electrical machine while the control of the current of the harmonic is released, c) transforming the current measurements using VSD to obtain a current signature of the harmonic, and d) determining whether a fault is present in the electrical machine or the power converter based on a comparison of the current signature with a reference current signature of the harmonic.