Vol. 337 No. 6 (2026)
DOI https://doi.org/10.18799/24131830/2026/6/5707
Controlled shift of a neutral point of a cascaded high-voltage frequency converter: control strategy, simulation, and experimental verification
Relevance. The failure of a power cell in a cascaded H-bridge high-voltage variable frequency drive causes phase voltage asymmetry and triggers instantaneous protection systems, which at remote oil and gas facilities leads to multi-day shutdowns of process equipment. The traditional approach to restoring operability based on hardware redundancy increases equipment costs by 15–25%. Aim. Development and experimental verification of a software algorithm for controlled neutral point shifting in a cascaded multilevel inverter, ensuring symmetry of line-to-line voltages at the load under emergency operation when faulty power cells are bypassed without the use of hardware redundancy. Methods. The balancing algorithm is integrated into a conventional field-oriented control system for a three-phase AC motor by modifying the inverse Clarke transformation matrix. For a 13-level cascaded H‑bridge inverter, the computational process for finding the desired neutral point shift is automated by solving a system of high-order nonlinear equations. A simulation model is developed in MATLAB/Simulink with adaptive recalculation of the phase shifts of the carrier signal generators for scalar pulse width modulation with a triangular instantaneous waveform, implemented according to the phase-shifted pulse width modulation principle. Experimental verification of the developed algorithmic principles for line voltage balancing was performed on an industrial test bench at ZAO «ERASIB», Novosibirsk, based on a production model of the «ERATON-V» drive (6 cells per phase, 1140 V) and a 30 kW induction motor. Results and conclusions. Digital simulation confirms that the proposed adaptive recalculation of phase shifts preserves the instantaneous harmonic shape of the phase currents when cells are bypassed. For configurations 5-6-6, 5-5-6, and 5-5-5, the reduction in line voltage ranges from 5.8 to 16.6%, which is acceptable for pump and fan loads. The algorithm operability is experimentally confirmed for the failure of one, two, and three cells, as the control system automatically ensures symmetry of line voltages and sinusoidal stator currents of the electrical machine without hardware redundancy. The discrepancy between experimental data and simulation results does not exceed the engineering accuracy level of 5%, allowing this technical solution to be used in production models of the «ERATON-V» drive.
For citation: Sidorov G. S., Nos O. V. Controlled shift of a neutral point of a cascaded high-voltage frequency converter: algorithm, simulation and experimental verification on industrial equipment. Bulletin of the Tomsk Polytechnic University. Geo Assets Engineering, 2026, vol. 337, no. 6, pp. 188-202. https://doi.org/10.18799/24131830/2026/6/5707
Keywords:
multilevel voltage source inverter, cascaded H-bridge, emergency operation mode, redundancy, control algorithms, neutral point shifting
References:
1. Ranjbar Y., Nemati A. Intelligence analytics in Industry 4.0: IoT-based oil and gas industry. Journal of Industrial Information Integration, 2026, vol. 1, p. 39. DOI: 10.1016/j.iotcps.2026.03.004.
2. Nguyen M.L., Ta D.A. Synchronous transfer control of medium voltage pump in water treatment: a multilevel cascaded H-bridge inverter-based solution. Results in Engineering, 2025, p. 11. DOI: 10.1016/j.rineng.2025.107006.
3. Antunes H.M.A., Brandao D.I., Biajo V.H.M., Oliveira F.S., Silva S.M. Floating, production, storage, and offloading unit: a contingency operating mode using variable frequency drives. IEEE Access, 2024, vol. 12, p. 11. DOI: 10.1109/ACCESS.2024.3400686.
4. Tender No. 71310781: Current repair of the control system of Siemens variable frequency drives at the facilities of Transneft – Vostok LLC. RosTender. 26.10.2023. (In Russ.) Available at: https://rostender.info/region/irkutskaya-oblast/bratsk/71310781-tender-tekushchij-remont-sistemy-upravleniya-chastotno-reguliruemyh-privodov-simens-obektov-ooo-transneft-vostok#desc (accessed 5 April 2026).
5. Tender No. 55736180: Current repair of ABB variable frequency drives at the facilities of Lensky RNU. RosTender. 22.10.2021. (In Russ.) Available at: https://rostender.info/region/irkutskaya-oblast/kirensk/55736180-tender-tekushchij-remont-chrp-proizvodstva-avv-obektov-lenskogo-rnu (accessed 5 April 2026).
6. Morawiec M., Lewicki A. Power electronic transformer based on cascaded H-bridge converter. Bulletin of the Polish Academy of Sciences: Technical Sciences, 2017, vol. 65, no. 5, pp. 675–683. DOI: 10.1515/bpasts-2017-007.
7. Zhao F., Xu H., Chen X., Wang Y. Power balance control strategy of cascaded h-bridge multilevel inverter based on improved harmonic injection. TSP_EE_68714, 2025, p. 14. DOI: 10.32604/ee.2025.068714.
8. Wang C., Chen W., Fang X., Ma X., Li X., Zhang K., Wang H., Peng H., Li L. DC infeed fault ride-through operation of cascaded H-bridge multilevel inverter based on DC-coupled thyristors. International Journal of Electrical Power and Energy Systems, 2026, vol. 177, p. 19. DOI: 10.1016/j.ijepes.2026.111796.
9. Phukan H., Pati A., Singh J., Bizon N. Review of fault detection, localization and tolerant in multilevel inverter. Energy Reports, 2026, vol. 15, p. 24. DOI: 10.1016/j.egyr.2026.109038.
10. Vinogradov A.B., Korotkov A.A. Control algorithms for high-voltage multilevel frequency converter. Ivanovo, Ivanovo State Power Engineering University Publ., 2018. 184 p. (In Russ.)
11. Yang S. Condition monitoring for device reliability in power electronic converters: a review. IEEE Transactions on Power Electronics, 2010, vol. 25, no. 11, pp. 2734–2752. DOI: 10.1109/TPEL.2010.2049377.
12. Sivapriya A., Nallathambi K. An extensive review on fault detection and fault-tolerant control of multi-level inverter with applications. International Journal of Renewable Energy Research, 2022, vol. 12, no. 30, pp. 768–798.
13. Gatta R.K., Kumar D.G., Shashavali P., Dsnm R., Kotb H., Alkuhayli A., Ghadi Y.Y., Mbasso W.F. Comprehensive analysis of faults and diagnosis techniques in cascaded multi-level inverters. Heliyon, 2024, vol. 10, no. 22, p. 25. DOI: 10.1016/j.heliyon.2024.e39901.
14. Dong L., Xiao Q., Jia Y., Fang T. Review of research on intelligent diagnosis of oil transfer pump malfunction. Natural Gas Industry B, 2023, vol. 10, no. 2, pp. 135–142. DOI: 10.1016/j.ngib.2022.04.002.
15. Sidorov G.S. Control of multilevel frequency converters based on cascaded H-bridges in emergency modes of high-voltage electric drive. Proceedings of the All-Russian Scientific and Practical Conference. Information and Telecommunication Systems and Technologies. Kemerovo, 2025. pp. 483–487. (In Russ.)
16. Spare on demand power cells for modular multi-level power converter. Patent EU, no. 3300240 A1, 2018.
17. Fault control method for converter. Patent CN, no. 101699732 B, 2012. (In Chin.)
18. Kopyrin V.A., Khamitov R.N., Glazyrin A.S., Kladiev S.N., Rakov I.V., Portnyagin A.L., Markova A.A. Assessing the total cost of ownership of an electric submersible pump unit with a downhole compensator. Bulletin of the Tomsk Polytechnic University. Geo Assets Engineering, 2021, vol. 332, no. 2, pp. 166–175. (In Russ.) DOI: 10.18799/24131830/2021/02/3053.
19. Ceballos S. Fault-tolerant hybrid four-leg multilevel converter. 2007 European Conference on Power Electronics and Applications. Aalborg, Denmark, IEEE, 2007. pp. 1–9. DOI: 10.1109/EPE.2007.4417617.
20. He J. A fault-tolerant T-type multilevel inverter topology with increased overload capability and soft-switching characteristics. IEEE Transactions on Industry Applications, 2017, vol. 53, no. 3, pp. 2826–2839. DOI: 10.1109/TIA.2017.2665630.
21. Zhang W. Survey on fault-tolerant techniques for power electronic converters. IEEE Transactions on Power Electronics, 2014, vol. 29, no. 12, pp. 6319–6331. DOI: 10.1109/TPEL.2014.2304561.
22. Lakhdari M., Rabhi B., Benaissa A. A new structural reconfiguration for multilevel inverters with fault tolerance capability. Acta Polytechnica, 2024, vol. 64, no. 4, pp. 379–384. DOI: 10.14311/AP.2024.64.0379.
23. Jeongwoo K., Younghoon C. Improved neutral shift method for fault tolerant operation of three phase MLCI. Journal of Power Electronics, 2021, vol. 21, no. 8, pp. 49–58. DOI: 10.1007/s43236-020-00161-0.
24. Nos O.V., Abramushkina E.E. The control technique for cascaded H-bridge multilevel converter with faulty cells. The 19 international conference of young specialists on micro/nanotechnologies and electron devices, EDM 2018: proc. Erlagol, Altai, 29 June – 3 July 2018. IEEE Computer Society, 2018. pp. 672–675. DOI: 10.1109/EDM.2018.8435054.
25. Nos O.V., Dybko M.A., Nos N.I. Control algorithms for cascaded H-bridge multilevel voltage inverter in emergency operation. Elektrotekhnika, 2021, no. 12, pp. 37–47. (In Russ.)
26. Hammond P.W. Enhancing the reliability of modular medium-voltage drives. IEEE Transactions on Industrial Electronics, 2002, vol. 49, no. 5, pp. 948–954. DOI: 10.1109/TIE.2002.803172.
27. Eaton D., Rama J., Hammond P. Neutral shift: five years of continuous operation with adjustable frequency drives. IEEE Industry Applications Magazine, 2003, vol. 9, no. 6, pp. 47–54. DOI: 10.1109/MIA.2003.1245795.
28. Vinogradov A.B. Vector control of AC electric drives. Ivanovo, Ivanovo State Power Engineering University Publ., 2008. 298 p. (In Russ.)
29. Sidorov G.S. Solving the problem of line voltage balancing for cascaded inverters in emergency operation. Mechatronics, Automation and Robotics: Proceedings of the International Scientific and Practical Conference. ¬¬St Petersburg, 2026. No. 17, pp. 238–245. (In Russ.) DOI: 10.26160/2541-8637-2026-17-238-245.
30. Sidorov G.S., Nos O.V. Certificate of state registration of computer program no. 2026614056. Program for calculating the elements of the coordinate transformation matrix of a three-phase voltage system from orthogonal components for various combinations of faulty power cells of a multilevel inverter, no. 2026613158, 2026. (In Russ.)
31. Pankratov V.V., Kotin D.A. Adaptive algorithms for sensorless vector control of asynchronous electric drives of lifting and transport mechanisms. Novosibirsk, NSTU Publ., 2018. 125 p. (In Russ.)
32. Rao J.V., Mahesh A. Hardware implementation of carrier rotation strategy for Cascaded H-bridge multilevel inverters. 2017 International Conference on Computing, Communication and Automation (ICCCA). Greater Noida, IEEE, 2017. pp. 1578–1583. DOI: 10.1109/CCAA.2017.8230055.
33. Domakhin E.A. Control algorithms for high-voltage asynchronous electric drive with function of bumpless load switching to the supply network. Cand. Diss. Novosibirsk, 2022. 174 p. (In Russ.)
34. Mouzhi Dong. A novel digital modulation scheme for multilevel cascaded H-bridge inverters. 2008 IEEE Power Electronics Specialists Conference – PESC 2008. Rhodes, Greece, IEEE, 2008. pp. 1675–1680. DOI: 10.1109/PESC.2008.4592182.
35. Ma M., Hu L., Chen A., He X. Reconfiguration of carrier-based modulation strategy for fault tolerant multilevel inverters. IEEE Transactions on Power Electronics, 2007, vol. 22, no. 5, pp. 2050–2060. DOI: 10.1109/TPEL.2007.904249.
36. Choi J.-Y., Han B.-M. An improved phase-shifted carrier PWM for modular multilevel converters with redundancy sub-modules. Journal of Power Electronics, 2016, vol. 16, no. 2, pp. 473–479. DOI: 10.6113/JPE.2016.16.2.473.
