Analysis of Quasi-Two-Level Modulation for Neutral-Point-Clamped Three-level Converter with 10 kV SiC MOSFETs
Analysis of Quasi-Two-Level Modulation for Neutral-Point-Clamped Three-level Converter with 10 kV SiC MOSFETs
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DOI：
10.23919/epe21ecceeurope50061.2021.9570662
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
Xiang Lin;D. Dong
中科院分区：
文献类型：
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作者：
Xiang Lin;D. Dong
为了提高开关器件的阻断电压水平以提高功率变换器的电压等级，功率半导体器件的串联是一种有吸引力的解决方案。但它存在电压不平衡问题，导致可靠性问题。为了避免直接串联，本文提出了两个串联 SiC MOSFET 的替代解决方案：基于中性点钳位 (NPC) 三电平 (3L) 转换器的准二电平 (Q2L) 调制。由于以下几个原因，所提出的解决方案对于最近的 10 kV SiC MOSFET 非常有吸引力：1）阻断电压可以增加到 20 kV，适合大多数中压应用； 2）采用NPC 3L结构，避免了串联器件的电压平衡问题； 3) 通过 Q2L 调制，钳位二极管的总损耗显着降低，因此钳位二极管不会显着增加转换器体积。本文将讨论基本调制策略及其对直流母线电容器电压平衡的影响。采用Q2L调制时，选择体积小得多的串联3.3 kV SiC二极管作为钳位二极管，以展示Q2L调制的优点。同时，对 NPC 3L 转换器和飞跨电容 (FC) 3L 转换器的 Q2L 调制进行了详细比较。进行单相泵回测试以演示 Q2L 调制及其对钳位二极管损耗的影响。
To increase the blocking voltage level of switching device to improve the voltage class of power converters, series-connection of power semiconductor devices is an attractive solution. But it suffers voltage unbalance problem leading to reliability concerns. To avoid the direct series-connection, this paper presents an alternative solution for two series-connected SiC MOSFETs: quasi-two-level(Q2L) modulation based on the neutral-point-clamped (NPC) three-level (3L) converter. The proposed solution is very attractive for the recent 10 kV SiC MOSFETs due to several reasons: 1) the blocking voltage could be increased to 20 kV, suitable for most medium voltage applications; 2) with NPC 3L structure, the voltage balancing of series-connected devices is avoided; 3) with Q2L modulation, the total loss on clamping diodes is significantly reduced so the clamping diodes don’t significantly increase converter volume. In this paper, the basic modulation strategy and its impact on the voltage balancing of dc bus capacitors will be discussed. With Q2L modulation, series-connected 3.3 kV SiC diodes with much smaller volume are chosen as an example as the clamping diodes to showcase the benefit of Q2L modulation. Meanwhile, the detail comparison of Q2L modulation is presented between NPC 3L converter and flying capacitor (FC) 3L converter. Single-phase pump-back test is conducted to demonstrate the Q2L modulation and its impact on clamping diode loss.