Comparison of Performance Fault-Tolerant Five Level Inverter with and without PWM Technique Multilevel Inverter

Abstract

Five-level Neutral Point Clamped (NPC) inverters are widely utilized in high-power and industrial systems due to their ability to generate high-quality output waveforms, minimize Total Harmonic Distortion (THD), and evenly distribute voltage stress across semiconductor switches. Despite these advantages, their intricate topology makes them vulnerable to faults such as open-circuit switches, diode failures, and imbalanced capacitor voltages. Such faults can severely impact output performance, cause waveform distortion, and potentially lead to complete system failure, particularly in precision-demanding environments like motor drives and industrial controls. This paper investigates the fault behaviour of conventional five-level NPC inverters and contrasts their performance with a Pulse Width Modulation (PWM)-based fault-tolerant inverter design. Traditional fault mitigation approaches often rely on additional hardware or redundancy, increasing both complexity and cost. In contrast, the proposed method employs a control-centric strategy using PWM to dynamically adapt switching states in the presence of faults, ensuring balanced voltage output and reduced harmonic distortion without requiring extra components. Comprehensive simulations were carried out under several fault scenarios, including single-switch failures, clamping diode defects, and imbalanced DC-link conditions. The analysis focuses on key performance indicators such as output voltage quality, THD levels, and system recovery response. The results reveal that the PWM-controlled fault-tolerant inverter consistently outperforms its conventional counterpart in maintaining waveform stability and overall reliability under fault conditions. This study emphasizes the effectiveness of PWM-based control strategies in enhancing the fault resilience and operational efficiency of five-level NPC inverter systems.

Introduction

Multilevel inverters (MLIs), especially Neutral Point Clamped (NPC) types, are widely used in medium and high-power applications due to their ability to generate near-sinusoidal output voltages with low harmonic distortion and reduced stress on components. Five-level NPC inverters offer improved waveform quality and lower Total Harmonic Distortion (THD) compared to three-level versions but increase circuit complexity and hardware failure risks.

Traditional five-level NPC inverters lack real-time fault-handling, which can lead to voltage imbalance, waveform distortion, and system reliability issues during faults such as switch or diode failures. To address this, fault-tolerant inverter designs employ redundancy and intelligent switching strategies to maintain operation by switching from five-level to a degraded three-level mode when faults occur, often compensating for voltage drops using transformers.

The integration of Pulse Width Modulation (PWM) in fault-tolerant NPC inverters enhances fault handling by dynamically excluding faulty components and maintaining balanced output voltages without additional hardware, thus improving flexibility and cost efficiency.

Simulation results comparing conventional and PWM-based fault-tolerant five-level NPC inverters showed that the PWM approach yields lower THD and better voltage waveform quality in both fault-free and fault conditions, confirming its effectiveness in maintaining inverter performance and reliability during faults.

Conclusion

The results clearly demonstrate that traditional fault-tolerant five-level NPC inverters show noticeable performance decline when faults such as switch failures, diode malfunctions, or DC-link imbalances occur. These faults cause increased harmonic distortion, voltage imbalance, and disruption in output waveforms, limiting the reliability of the system in critical applications. On the other hand, the fault-tolerant NPC inverter controlled by PWM succeeded in dealing with fault conditions by adjusting the switching patterns and reassigning voltage levels to operating devices. Simulation and experimental results confirmed that the system guaranteed stability of the waveform, minimized THD, and sustained continuous operation even with hardware faults. This stable operation in tough conditions highlights the inverter\'s suitability to high-load applications like industrial motor drives and Grid systems. The control strategy, without adding significant hardware complexity, enhances the inverter\'s reliability and renders it a feasible and efficient

References

[1] B. Anil Kumar1, B.Rohith2, P. Karthikeya3, N. Rahul4, T. Murali Krishna5” Comparative Analysis of Conventional and Fault- Tolerant Five-Level NPC Inverters” DOI Link: https://doi.org/10.22214/ijraset.2025.69755 Apr 2025. [2] J. Rodríguez, J. Lai, and F. Z. Peng, \"Multilevel inverters: a survey of topologies, controls, and applications,\" IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 724–738, Aug. 2002. [3] L. M. Tolbert, F. Z. Peng, and T. G. Habetler, \"Multilevel converters for large electric drives,\" IEEE Trans. Ind. Appl., vol. 35, no. 1, pp. 36–44, Jan.–Feb. 1999.Wikipedia [4] B. Wu, \"High-Power Converters and AC Drives,\" Wiley-IEEE Press, 2006. [5] M. Malinowski, K. Gopakumar, J. Rodriguez, and M. A. Pérez, \"A survey on cascaded multilevel inverters,\" IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2197–2206, Jul. 2010. [6] S. Kouro et al., \"Recent advances and industrial applications of multilevel converters,\" IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553–2580, Aug. 2010. [7] P. Lezana, R. Aguilera, and D. E. Quevedo, \"Model predictive control of an asymmetric flying capacitor converter,\" IEEE Trans. Ind. Electron., vol. 56, no. 6, pp. 1839–1846, Jun. 2009. [8] A. Nabae, I. Takahashi, and H. Akagi, \"A new neutral-point-clamped PWM inverter,\" IEEE Trans. Ind. Appl., vol. IA-17, no. 5, pp. 518–523, Sep. 1981. [9] H. Akagi, \"Classification, terminology, and application of the modular multilevel cascade converter (MMCC),\" IEEE Trans. Power Electron., vol. 26, no. 11, pp. 3119–3130, Nov. 2011. [10] J. Holtz, \"Pulsewidth modulation for electronic power conversion,\" Proc. IEEE, vol. 82, no. 8, pp. 1194–1214, Aug. 1994. [11] K. Gopakumar, S. K. Sahoo, and B. K. Bose, \"A new switching strategy for a three-level inverter,\" IEEE Trans. Ind. Electron., vol. 44, no. 3, pp. 411–418, Jun. 1997. [12] M. Marchesoni and M. Mazzucchelli, \"Multilevel converters for high power AC drives: a review,\" in Proc. IEEE Int. Symp. Ind. Electron., 1993, pp. 38–43. [13] E. Babaei, \"A cascade multilevel converter topology with reduced number of switches,\" IEEE Trans. Power Electron., vol. 23, no. 6, pp. 2657–2664, Nov. 2008. [14] S. Khomfoi and L. M. Tolbert, \"Multilevel power converters,\" in Power Electronics Handbook, 2nd ed., Elsevier, 2007, pp. 451–482. [15] M. F. Escalante, J. C. Vannier, and A. Arzandé, \"Flying capacitor multilevel inverters and DTC motor drive applications,\" IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 809–815, Aug. 2002. [16] H. Abu-Rub, J. Holtz, J. Rodriguez, and G. Baoming, \"Medium-voltage multilevel converters—state of the art, challenges, and requirements in industrial applications,\" IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2581–2596, Aug. 2010. [17] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B. Wu, J. Rodriguez, M. A. Pérez, and J. I. Leon, \"Recent advances and industrial applications of multilevel converters,\" IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 255 [18] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B. Wu, J. Rodriguez, M. A. Perez, and J. I. Leon, “Recent Advances and Industrial Applications of Multilevel Converters,” IEEE Transactions on Industrial Electronics, vol. 57, no. 8, pp. 2553–2580, Aug. 2010. DOI: 10.1109/TIE.2010.2049719 [19] R. Teodorescu, F. Blaabjerg, M. Liserre, and P. C. Loh, “Proactive Fault Tolerant Systems with Distributed Power Converters,” IEEE Transactions on Power Electronics, vol. 23, no. 5, pp. 2681–2692, Sept. 2008.DOI: 10.1109/TPEL.2008.2002705 [20] M. Khazraei, M. Ferdowsi, and K. Corzine, “Fault Diagnosis and Fault-Tolerant Control of Multilevel Inverters Using Artificial Neural Networks,” IEEE Transactions on Industrial Electronics, vol. 60, no. 6, pp. 2133–2141, June 2013. DOI: 10.1109/TIE.2012.2206361 [21] Y. Chen and Z. Yuan,“Design and Implementation of a Fault-Tolerant NPC Inverter with Redundant Components,”IEEE Transactions on Industrial Electronics, vol. 62, no. 1, pp. 421–429,Jan.2015.DOI: 10.1109/TIE.2014.2336594

Copyright

Copyright © 2025 N. Rahul, T. Murali Krishna, B. Anil Kumar, B. Rohith, P. Karthikeya. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.