Reduced Switching-Frequency Modulation and Circulating Current Suppression for Modular Multilevel Converters
Reduced Switching-Frequency Modulation and Circulating Current Suppression for Modular Multilevel Converters
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DOI：
10.1109/tpwrd.2011.2115258
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发表时间：
2011-04
影响因子：
4.4
通讯作者：
Qingrui Tu;Zheng Xu;Lie Xu
中科院分区：
文献类型：
--
作者：
Qingrui Tu;Zheng Xu;Lie Xu
提出了一种适用于模块化多电平变换器（MMC）的改进相移载波脉宽调制（PSC-PWM）方案。为了降低器件的平均开关频率，提出了一种降低开关频率（RSF）的电压平衡算法。本文还提出了一种环流抑制控制器（CCSC），以最大限度地减少MMC的内部环流。基于双工频负序旋转坐标系，将三相交流环流分解为两个直流分量，并通过一对比例积分控制器使其最小化。基于PSCAD/EMTDC详细模型的仿真结果证明了改进的PSC-PWM方法和RSF电压平衡算法的有效性。所提出的CCSC不仅消除了内环流，而且改善了变换器交流输出电压的质量。一个简单的损耗评估表明，RSF电压平衡算法和CCSC降低了变换器的功率损耗。
This paper describes a modified phase-shifted carrier-based pulsewidth-modulation (PSC-PWM) scheme for modular multilevel converters (MMC). In order to reduce the average device switching frequency, a reduced switching-frequency (RSF) voltage balancing algorithm is developed. This paper also proposes a circulating current suppressing controller (CCSC) to minimize the inner circulating current in an MMC. Based on the double line-frequency, negative-sequence rotational frame, the three-phase alternative circulating currents are decomposed into two dc components and are minimized by a pair of proportional integral controllers. Simulation results based on a detailed PSCAD/EMTDC model prove the effectiveness of the modified PSC-PWM method and the RSF voltage-balancing algorithm. The proposed CCSC not only eliminates the inner circulating current but also improves the quality of the converter ac output voltage. A simple loss evaluation demonstrates that the RSF voltage-balancing algorithm and the CCSC reduce the converter power losses.