Comparison of Frequency Transform Methods for Condition Monitoring of a DC-Link Capacitor

Raqib, Abdurrahman; Jahanger, Hayder; Sumner, Mark; Cox, Tom; Klumpner, Christian; Agha, Imran; Kenney, Richard; Aguilar, Fernando; Lonsdale, Peter

Abstract

Electrolytic capacitors continue to be used for the DC-link in motor drive systems due to their high specific capacitance. The degradation of electrolytic capacitors can lead to increased equivalent series resistances (ESR) and reduction in capacitance. This can impair the drive behaviour (e.g., reducing the ability of the motor-drive to maintain a steady voltage and thereby maintain steady speed set-points), but will also lead to additional heating and a further cycle of degradation until failure occurs. On-line condition monitoring is useful to understand and predict failure, and can potentially be embedded into a more holistic condition monitoring regime through, for example, the Internet of Things (IoT). It is possible to measure and track currents and voltages through the DC-link and estimate in real-time the corresponding capacitor impedances. The method proposed in this paper will estimate the impedance in a frequency related domain to ensure that the proposed approach is robust to changes in operating conditions - load variation, ambient temperature, drive temperature - and also allow the impedance to be estimated over a wide frequency range. Therefore, different transform methods have been investigated: the Fast Fourier Transform (FFT); the Short-Term Fourier Transform (STFT); and the Continous Wavelet Transform (CWT), making use of two different mother wavelets (complex and bump). It was found that the CWT provided optimal results with fine granularity in time, although selection of a mother wavelet may lead to loss of salient information.

Citation

Raqib, A., Jahanger, H., Sumner, M., Cox, T., Klumpner, C., Agha, I., Kenney, R., Aguilar, F., & Lonsdale, P. (2020, December). Comparison of Frequency Transform Methods for Condition Monitoring of a DC-Link Capacitor. Presented at 10th International Conference on Power Electronics, Machines and Drives (PEMD 2020), Online Conference

• Presentation Conference Type: Edited Proceedings
• Conference Name: 10th International Conference on Power Electronics, Machines and Drives (PEMD 2020)
• Start Date: Dec 15, 2020
• End Date: Dec 17, 2020
• Acceptance Date: Nov 6, 2019
• Online Publication Date: Sep 22, 2021
• Publication Date: Sep 22, 2021
• Deposit Date: Feb 16, 2022
• Publicly Available Date: Feb 16, 2022
• Pages: 621 – 626
• Series Title: International Conference on Power Electronics, Machines and Drives (PEMD)
• Book Title: 10th International Conference on Power Electronics, Machines and Drives (PEMD 2020)
• ISBN: 9781839535420
• DOI: https://doi.org/10.1049/icp.2021.1169
• Public URL: https://nottingham-repository.worktribe.com/output/7470211
• Publisher URL: https://ieeexplore-ieee-org.nottingham.idm.oclc.org/document/9545362
• Related Public URLs: https://digital-library.theiet.org/content/conferences/10.1049/icp.2021.1169
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