scholarly journals A Study on Common Mode Voltage Reduction Strategies According to Modulation Methods in Modular Multilevel Converter

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1607
Author(s):  
Chang-Hwan Park ◽  
In-Kyo Seo ◽  
Belete Belayneh Negesse ◽  
Jong-su Yoon ◽  
Jang-Mok Kim
Keyword(s):  
Electromagnetic Interference ◽  
Experimental Result ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Frequent Change ◽  
Common Mode ◽  
Medium Voltage ◽  
Low Level ◽  
Common Mode Voltage ◽  
Switching State

Low level modular multilevel converter (MMC) is a promising candidate for medium voltage applications such as MVDC (medium voltage DC current) transmission and megawatt machine drives. Unlike high-level MMC using nearest level modulation (NLM), the low-level MMC using the pulse width modulation (PWM) or NLM + PWM is affected by a common mode voltage (CMV) due to a frequent change of a switching state. This CMV causes electromagnetic interference (EMI) noise, common mode current (CMC) and bearing current leading to a reduction in the efficiency and durability of the motor drive system. Therefore, this paper provides a mathematical analysis on how the switching state affects the CMV and proposes three software based CMV reduction algorithms for the low level MMC system. To reflect the characteristic of MMC modulation strategy for upper and lower reference voltage independently, two separate space vectors are used. Based on the analysis, three different CMV reduction algorithms (complete CMV reduction (CCR), DPWM CMV reduction (DCR) and partial CMV reduction (PCR)) are proposed using NLC + PWM modulation strategy. The performance of the proposed CMV reduction algorithms was verified by both simulation and experimental result.

scholarly journals Improved Synchronized Space Vector PWM Strategy for Three-Level Inverter at Low Modulation Index

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1400
Author(s):  
Xin Gu ◽  
Bingxu Wei ◽  
Guozheng Zhang ◽  
Zhiqiang Wang ◽  
Wei Chen
Keyword(s):  
Modulation Index ◽  
Voltage Amplitude ◽  
Switching Loss ◽  
Space Vector Pwm ◽  
Space Vector ◽  
Common Mode ◽  
Medium Voltage ◽  
Common Mode Voltage ◽  
The Common ◽  
Switching State

Aimed at reducing the switching loss and common-mode voltage amplitude of high-power medium-voltage three-level inverter under low modulation index conditions, an improved synchronous space vector PWM strategy is proposed in this paper. The switching times in each fundamental period are reduced by the re-division of small regions and the full use of the redundant switching state. The sum of switching algebra is introduced as an evaluation index and the switching state with the minimum value of the sum of switching algebra are adopted. Then, the common mode voltage amplitude is reduced. The theoretical analysis and experimental results show that the improved modulation strategy proposed in this paper can effectively reduce the switching loss and common-mode voltage amplitude of the inverter under the condition of the low modulation index. Moreover, the neutral-point voltage ripple is also reduced simultaneously.

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