A Low-Switching-Frequency Harmonic-Optimized Control Strategy for Modular Multilevel Converters Based on Online SHEPWM Switching-Time Correction.
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| Title: | A Low-Switching-Frequency Harmonic-Optimized Control Strategy for Modular Multilevel Converters Based on Online SHEPWM Switching-Time Correction. |
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| Authors: | Lyu, Tingyan1,2 (AUTHOR), Tang, Bojin1,2 (AUTHOR), Deng, Youhan1,2,3 (AUTHOR), Hua, Xiaojun1,3,4 (AUTHOR), Kang, Rong1,2 (AUTHOR), Yao, Weiwei1,2 (AUTHOR), Hao, Yaru1,3 (AUTHOR), Li, Chunyang4 (AUTHOR), Yuan, Huilin4 (AUTHOR) linhayes@whu.edu.cn |
| Source: | Energies (19961073). Sep2026, Vol. 19 Issue 18, p4434. 33p. |
| Subject Terms: | *Pulse width modulation, *Electric current converters |
| Abstract: | Low-switching-frequency operation is essential for high-power modular multilevel converters (MMCs), but it makes the simultaneous achievement of low harmonics, fast transient response, and reliable internal control more difficult. Conventional lookup-table selective harmonic elimination PWM (SHEPWM) preserves steady-state harmonic optimization, yet its fundamental-period pattern update limits transient flexibility; predictive pulse-pattern methods improve current or flux tracking, but do not directly coordinate the MMC execution chain from arm-level pulse displacement to physical submodule gating. This paper proposes a coordinated switching-event control scheme for SHEPWM-based MMCs. The offline harmonic-optimized pattern is used as the steady-state backbone, while selected time-stamped events are corrected online through a virtual-flux formulation. The same events are then processed by causal pulse-edge compensation, paired upper/lower-arm displacement for circulating-current suppression, and threshold-based asynchronous submodule scheduling. Simulations of startup, active-power steps, and power-flow reversal show that more than 90% of the virtual-flux error is compensated within approximately 5 ms. Device-level co-simulation reduces current THD from 1.5881% to 0.702%, and paired-event control reduces arm-current THD from 21.600% to 4.9266%. At rated steady state, the method achieves 1.25% grid-current THD with a 50 Hz average submodule switching frequency, supporting low-loss MMC operation without abandoning SHEPWM harmonic optimization. [ABSTRACT FROM AUTHOR] |
| Database: | Energy & Power Source |
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| Abstract: | Low-switching-frequency operation is essential for high-power modular multilevel converters (MMCs), but it makes the simultaneous achievement of low harmonics, fast transient response, and reliable internal control more difficult. Conventional lookup-table selective harmonic elimination PWM (SHEPWM) preserves steady-state harmonic optimization, yet its fundamental-period pattern update limits transient flexibility; predictive pulse-pattern methods improve current or flux tracking, but do not directly coordinate the MMC execution chain from arm-level pulse displacement to physical submodule gating. This paper proposes a coordinated switching-event control scheme for SHEPWM-based MMCs. The offline harmonic-optimized pattern is used as the steady-state backbone, while selected time-stamped events are corrected online through a virtual-flux formulation. The same events are then processed by causal pulse-edge compensation, paired upper/lower-arm displacement for circulating-current suppression, and threshold-based asynchronous submodule scheduling. Simulations of startup, active-power steps, and power-flow reversal show that more than 90% of the virtual-flux error is compensated within approximately 5 ms. Device-level co-simulation reduces current THD from 1.5881% to 0.702%, and paired-event control reduces arm-current THD from 21.600% to 4.9266%. At rated steady state, the method achieves 1.25% grid-current THD with a 50 Hz average submodule switching frequency, supporting low-loss MMC operation without abandoning SHEPWM harmonic optimization. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 19961073 |
| DOI: | 10.3390/en19184434 |
