在工業4.0和智慧化的趨勢下，工廠需要透過線上監控系統使得保養操作得以最佳化。且現階段許多工廠都是透過感應馬達來當動力傳遞的來源。然而，許多產業為了節省能源成本，感應馬達前端通常會接上變頻器以便去達到節能運轉的控管。此舉往往會造成嚴重的諧波(Harmonic)現象，而為了保護感應馬達，會在變頻器輸出端加裝輸出濾波器(Output Filter)。因此為防範輸出濾波器失效間接導致感應馬達的壽命降低，監控濾波器的狀況有其重要性與必要性。
在輸出濾波器損壞率最高的元件則是電容器，而文獻中針對電容器的老化與異常監控有許多研究，但都必須要追加感測器才能達到此目的。本論文提出新的模型式方法透過變頻器的三相電壓感測器和電流感測器來監控濾波器中的電容器。研究中透過加熱方式來老化薄膜式電容器，再接上純電阻的負載和感應馬達的負載來做觀察，並且透過使用快速傅立葉轉換(Fast Fourier Transform)和子空間狀態空間數值演算法(Numerical algorithm for Subspace State Space System Identification)來分析出健康電容器和老化電容器的差別。

In the trend of industry 4.0 and artificial intelligence, many factories were motivated to install the online monitoring systems for optimal operation and maintenance. In recent years, the prime mover of factories is the induction motors. As a prime incentive to reduce energy consumption, factory owner is motivated to install the VFD (Variable-Frequency Drive) with those induction motors. However VFD generally induce the harmonic effect. Thus, an output filter is used in the VFD output to smooth the voltage output and to protect the running motor. The condition monitoring of the output filter is necessary because the failure and the degradation of the output filter will cause damage in induction motors.
The capacitors are the most frequently failed components in the output filter. Many literatures have documented the condition monitoring method for the capacitors and in most method additional sensors are required. In this research, a model-based approach is proposed for the condition monitoring of the output filter capacitors using only the 3-phase voltage and current measurement from the inverter output. The capacitors are aged by temperature baking.
Then the capacitors are used in the output filter of a VFD to drive a purely resistors load and an induction motor load. The voltage and current data are collected for the analysis of the different capacitor condition including the new capacitors and the aged capacitors. Two methods, the Fast Fourier Transform and the Numerical algorithm for Subspace State Space System Identification, are performed and respective result is compared.

[1] Danfoss, "VLT® FC-Serie Output Filter Design Guide," Accessed on: 2 22Available: http://files.danfoss.com/download/Drives/doc_MG90N504.pdf
[2] S. Manias, "11 - Passive and Active Filters," in Power Electronics and Motor Drive Systems: Academic Press, 2017, pp. 807-842.
[3] K. H. Ahmed, S. J. Finney, and B. W. Williams, "Passive filter design for three-phase inverter interfacing in distributed generation," in 2007 Compatibility in Power Electronics, 2007, pp. 1-9: IEEE.
[4] S. Karmakar, S. Chattopadhyay, M. Mitra, and S. Sengupta, Induction motor fault diagnosis. Springer, 2016.
[5] P. Sundararajan, M. H. M. Sathik, F. Sasongko, C. S. Tan, M. Tariq, and R. Simanjorang, "Online condition monitoring system for DC-link capacitor in industrial power converters," IEEE Transactions on Industry Applications, vol. 54, no. 5, pp. 4775-4785, 2018.
[6] G. Terzulli, "Film technology to replace electrolytic technology in wind power applications," AVX Technical Note, 2010.
[7] K. Harada, A. Katsuki, and M. Fujiwara, "Use of ESR for deterioration diagnosis of electrolytic capacitor," IEEE Transactions on Power Electronics, vol. 8, no. 4, pp. 355-361, 1993.
[8] V. Belko, D. Glivenko, O. Emelyanov, I. Ivanov, and A. Plotnikov, "Current Pulse Polarity Effect on Metallized Film Capacitors Failure," IEEE Transactions on Plasma Science, vol. 45, no. 6, pp. 1020-1025, 2017.
[9] Y.-M. Chen, H.-C. Wu, M.-W. Chou, and K.-Y. Lee, "Online failure prediction of the electrolytic capacitor for LC filter of switching-mode power converters," IEEE Transactions on Industrial Electronics, vol. 55, no. 1, pp. 400-406, 2008.
[10] H. Soliman, H. Wang, and F. Blaabjerg, "A review of the condition monitoring of capacitors in power electronic converters," IEEE Transactions on Industry Applications, vol. 52, no. 6, pp. 4976-4989, 2016.
[11] X. Pu, T.-H. Nguyen, D.-C. Lee, and S.-G. Lee, "Capacitance estimation of DC-link capacitors for single-phase PWM converters," in 2009 IEEE 6th International Power Electronics and Motion Control Conference, 2009, pp. 1656-1661: IEEE.
[12] J. Flicker, R. Kaplar, M. Marinella, and J. Granata, "Lifetime testing of metallized thin film capacitors for inverter applications," in 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013, pp. 3340-3342: IEEE.
[13] A. M. Amaral and A. M. Cardoso, "Using Newton-Raphson method to estimate the condition of aluminum electrolytic capacitors," in 2007 IEEE International Symposium on Industrial Electronics, 2007, pp. 827-832: IEEE.
[14] A. M. Imam, T. G. Habetler, R. G. Harley, and D. Divan, "Failure prediction of electrolytic capacitor using DSP methods," in Twentieth Annual IEEE Applied Power Electronics Conference and Exposition, 2005. APEC 2005., 2005, vol. 2, pp. 965-970: IEEE.
[15] S. Tang, S. Dong, Y. Liu, and Q. Zhang, "Current-sensorless online ESR monitoring of capacitors in boost converter," The Journal of Engineering, vol. 2019, no. 16, pp. 2569-2574, 2019.
[16] L. Ren, C. Gong, and Y. Zhao, "An online ESR estimation method for output capacitor of boost converter," IEEE Transactions on Power Electronics, vol. 34, no. 10, pp. 10153-10165, 2019.
[17] R. Khandebharad, R. Dhumale, and S. Lokhande, "Online Failure Prediction of the Aluminum Electrolytic Capacitor," International Journal of Science and Research, vol. 4, no. 6, pp. 2099-2102, 2015.
[18] L. Wu, Y. Guan, Y. Du, S. Zhou, and W. Pan, "Deterioration analysis of aluminum electrolytic capacitor for DC-DC converter," International Journal of the Physical Sciences, vol. 6, no. 7, pp. 1653-1664, 2011.
[19] H. Pang and P. M. Bryan, "A life prediction scheme for electrolytic capacitors in power converters without current sensor," in 2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2010, pp. 973-979: IEEE.
[20] Y. Yu, T. Zhou, M. Zhu, and D. Xu, "Fault diagnosis and life prediction of dc-link aluminum electrolytic capacitors used in three-phase ac/dc/ac converters," in 2012 Second International Conference on Instrumentation, Measurement, Computer, Communication and Control, 2012, pp. 825-830: IEEE.
[21] H. Wang, P. Davari, H. Wang, D. Kumar, F. Zare, and F. Blaabjerg, "Lifetime estimation of dc-link capacitors in adjustable speed drives under grid voltage unbalances," IEEE Transactions on Power Electronics, vol. 34, no. 5, pp. 4064-4078, 2018.
[22] G. M. Buiatti, J. A. Martin-Ramos, A. M. Amaral, P. Dworakowski, and A. J. M. Cardoso, "Condition monitoring of metallized polypropylene film capacitors in railway power trains," IEEE Transactions on Instrumentation and Measurement, vol. 58, no. 10, pp. 3796-3805, 2009.
[23] Y. Wu and X. Du, "A VEN condition monitoring method of DC-link capacitors for power converters," IEEE Transactions on Industrial Electronics, vol. 66, no. 2, pp. 1296-1306, 2018.
[24] P. Sundararajan et al., "Condition Monitoring of DC-Link Capacitors Using Goertzel Algorithm for Failure Precursor Parameter and Temperature Estimation," IEEE Transactions on Power Electronics, vol. 35, no. 6, pp. 6386-6396, 2019.
[25] H. Soliman, H. Wang, B. Gadalla, and F. Blaabjerg, "Condition monitoring for DC-link capacitors based on artificial neural network algorithm," in 2015 IEEE 5th International Conference on Power Engineering, Energy and Electrical Drives (POWERENG), 2015, pp. 587-591: IEEE.
[26] H.-J. Heo, W.-S. Im, J.-S. Kim, and J.-M. Kim, "A capacitance estimation of film capacitors in an LCL-filter of grid-connected PWM converters," Journal of Power Electronics, vol. 13, no. 1, pp. 94-103, 2013.
[27] S. C. Athikessavan, S. K. Panda, S. Nadarajan, and A. K. Gupta, "Diagnosis and Prognosis of LCL Filter in Marine Electric Propulsion Systems," in 2019 IEEE 13th International Conference on Power Electronics and Drive Systems (PEDS), 2019, pp. 1-5: IEEE.
[28] R. M. Tallam, R. J. Kerkman, and R. A. Lukaszewski, "Detection of Capacitor Degradation in LC Filters for AC Drives," IEEE Transactions on Industry Applications, vol. 51, no. 5, pp. 3822-3828, 2015.
[29] J. Koppinen, J. Kukkola, and M. Hinkkanen, "Parameter estimation of an LCL filter for control of grid converters," in 2015 9th International Conference on Power Electronics and ECCE Asia (ICPE-ECCE Asia), 2015, pp. 1260-1267: IEEE.
[30] Y. P. Patel, L. Wei, and R. J. Kerkman, "Filter capacitor degradation detection apparatus and method," 2017.
[31] M. El-Husseini, P. Venet, G. Rojat, and M. Fathallah, "Effect of the geometry on the aging of metalized polypropylene film capacitors," in 2001 IEEE 32nd Annual Power Electronics Specialists Conference (IEEE Cat. No. 01CH37230), 2001, vol. 4, pp. 2061-2066: IEEE.
[32] C. S. Kulkarni, J. R. Celaya, G. Biswas, and K. Goebel, "Accelerated aging experiments for capacitor health monitoring and prognostics," in 2012 IEEE AUTOTESTCON Proceedings, 2012, pp. 356-361: IEEE.
[33] R. J. a. p. a. Gallay, "Metallized film capacitor lifetime evaluation and failure mode analysis," 2016.
[34] A. Gupta, O. P. Yadav, D. DeVoto, and J. Major, "A Review of Degradation Behavior and Modeling of Capacitors," in International Electronic Packaging Technical Conference and Exhibition, 2018, vol. 51920, p. V001T04A004: American Society of Mechanical Engineers.
[35] M. Makdessi, A. Sari, P. Venet, P. Bevilacqua, and C. Joubert, "Accelerated ageing of metallized film capacitors under high ripple currents combined with a DC voltage," IEEE Transactions on Power Electronics, vol. 30, no. 5, pp. 2435-2444, 2014.
[36] M. J. J. S. S. B. Makdessi, "Modeling, ageing and health monitoring of metallized films capacitors used in power electronics applications," Journee Scientifique St. Bernard, vol. 11, pp. 1-5, 2012.
[37] R. Jánó and D. Pitică, "Accelerated ageing tests for predicting capacitor lifetimes," in 2011 IEEE 17th International Symposium for Design and Technology in Electronic Packaging (SIITME), 2011, pp. 63-68: IEEE.
[38] D. L. Jones, "The DFT, FFT, and practical spectral analysis," 2007.
[39] T. Katayama, Subspace methods for system identification. Springer Science & Business Media, 2006.
[40] SCHURTER, "Suppression Chokes DKIH-1," Accessed on: 05 12Available: https://www.schurter.com/en/datasheet/typ_DKIH-1.pdf
[41] KEMET, "R75, Single Metallized Polypropylene Film, Radial,DC and Pulse Applications (Automotive Grade)," Accessed on: 10 23Available: https://content.kemet.com/datasheets/KEM_F3106_R75.pdf