Modulation and Control for a New Hybrid Cascaded Multilevel Converter With DC Blocking Capability
Modulation and Control for a New Hybrid Cascaded Multilevel Converter With DC Blocking Capability
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DOI：
10.1109/pesmg.2013.6672273
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发表时间：
2013-07
影响因子：
4.4
通讯作者：
Yinglin Xue;Zheng Xu;Qingrui Tu
中科院分区：
文献类型：
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作者：
Yinglin Xue;Zheng Xu;Qingrui Tu
混合级联型多电平变换器是一种新型的具有隔直功能的电压源型变换器。它有两个关键部分，即由绝缘栅双极晶体管串联而成的导向开关（DS）和由全桥子模块（FSM）堆叠而成的波形整形电路（WSC）。本文重点研究了直扩系统和WSC的调制方案。首先，为了降低开关损耗，本文提出了一种新型的低频不对称方波调制方式，并分析了这种调制方式下WSC的能量流动。其次，提出了改进的相移载波脉宽调制（PSC-PWM）来确定要插入或旁路的FSM的数量，并根据电容电压平衡策略选择要激发的指定FSM。第三，研究了直流故障时限制短路电流的能力，设计了快速交流过流保护。PSCAD/EMTDC仿真验证了调制和控制策略的有效性。
The hybrid cascaded multilevel converter is a newly introduced voltage-source converter with dc blocking capability. It has two key parts, that is, the director switch (DS) made of insulated-gate bipolar transistors in series and the wave-shaping circuit (WSC) containing stacks of full-bridge submodules (FSMs). This paper focuses on the modulation schemes of the DSs and the WSCs. First, to reduce switching losses of the DSs, a novel asymmetrical square-wave modulation at a very low frequency is proposed, and the energy flow of the WSC under this modulation is analyzed. Second, modified phase-shifted carrier-based pulsewidth modulation (PSC-PWM) is presented to determine the number of FSMs to be inserted or bypassed; and the specified FSMs to be fired are selected according to the capacitor voltage-balancing strategy. Third, the capability to limit the short-circuit current during the dc fault is investigated, and fast ac overcurrent protection is designed. The effectiveness of the modulation and control strategies is verified by PSCAD/EMTDC simulations.