Modular multilevel converter (MMC) is the state-of-the-art converter topology in HVdc transmission applications. The reliability and lifetime of MMCs are strongly dependent on the health of the internal power semiconductors. The operating loss of power semiconductors, which is one of the dominant factors affecting component aging, is not uniformly distributed between the top and bottom switches in the same submodule (SM) due to the dc bias in the arm current. Such loss imbalance leads to differences in lifetime of semiconductors and reduces the reliability of SM. Especially under inverter conditions, the bottom insulated gate bipolar transistor (IGBT) in SM is subjected to a severe thermal stress and has a relatively high failure rate for the thermal vulnerability of IGBT. To extend the lifetime and improve the reliability, this article proposes a component-level loss balancing method. It is achieved by insertion index modification based on a feed-forward gain controller. The proposed method can improve the loss distribution among the top and bottom semiconductors without side effects on ac and dc outputs. Its effectiveness and feasibility are validated through simulation and experimental results.

中文翻译：

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通过插入指数修改实现基于 IGBT 的高功率 MMC 的元件级半导体损耗平衡


模块化多电平转换器 (MMC) 是 HVdc 传输应用中最先进的转换器拓扑。 MMC 的可靠性和寿命在很大程度上取决于内部功率半导体的健康状况。功率半导体的工作损耗是影响组件老化的主要因素之一，由于臂电流中的直流偏置，功率半导体的工作损耗在同一子模块（SM）的顶部和底部开关之间分布不均匀。这种损耗不平衡会导致半导体寿命的差异并降低SM的可靠性。特别是在逆变工况下，SM中的底部绝缘栅双极晶体管（IGBT）承受着严重的热应力，IGBT的热脆弱性故障率较高。为了延长使用寿命并提高可靠性，本文提出了一种元件级损耗平衡方法。它是通过基于前馈增益控制器的插入指数修改来实现的。所提出的方法可以改善顶部和底部半导体之间的损耗分布，而不会对交流和直流输出产生副作用。通过仿真和实验结果验证了其有效性和可行性。