A Low Inrush Current Pre-Charging Strategy of M3C with Improved Nearest Level Modulation

Rufei He, Yikai Li, Yumin Peng, Yiming Ma, Fanqi Huang, Hailong Li () and Wei Luo
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Rufei He: Energy Storage Research Institute of Southern Power Grid Peak Shaving and Frequency Modulation Power Generation Co., Ltd., Guangzhou 511493, China
Yikai Li: Energy Storage Research Institute of Southern Power Grid Peak Shaving and Frequency Modulation Power Generation Co., Ltd., Guangzhou 511493, China
Yumin Peng: Energy Storage Research Institute of Southern Power Grid Peak Shaving and Frequency Modulation Power Generation Co., Ltd., Guangzhou 511493, China
Yiming Ma: Energy Storage Research Institute of Southern Power Grid Peak Shaving and Frequency Modulation Power Generation Co., Ltd., Guangzhou 511493, China
Fanqi Huang: Energy Storage Research Institute of Southern Power Grid Peak Shaving and Frequency Modulation Power Generation Co., Ltd., Guangzhou 511493, China
Hailong Li: Shenzhen Hopewind Electric Co., Ltd., Shenzhen 518055, China
Wei Luo: Department of Electrical Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China

Energies, 2025, vol. 18, issue 11, 1-15

Abstract: The modular multilevel matrix converter (M3C) can perform AC/AC conversion directly. However, M3C operation often requires a pre-charging process, which can be challenging due to the need for fast pre-charging with low inrush current. To address the issue, a closed-loop fast pre-charging strategy is proposed that utilizes an improved nearest level modulation (NLM) based on a quick-sorting algorithm for M3C. By improving the current limiting resistor and the number of Sub-Modules (SMs) inserted into the NLM, we achieve a reduction in inrush current when connected to the grid, and unlock the control algorithm, respectively. This paper presents the relationship between the current-limiting resistor, the pre-charging current, and the pre-charging time. Reactive power compensation is applied on the AC grid during the pre-charging process to ensure stability. Furthermore, the balanced control of capacitor voltage is employed to achieve synchronized and coordinated growth of capacitor voltages in SMs using a quick-sorting algorithm based on NLM. The simulation and experimental results demonstrate the effectiveness of this approach, making it suitable for M3C with a high number of SMs.

Keywords: modular multilevel matrix converter (M3C); nearest level modulation (NLM); pre-charge; quick-sorting algorithm (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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