Due to the significant coupling of the internal dynamics on the ac-side in a modular multilevel converter (MMC), its terminal characteristics are quite different from a conventional two-level voltage source converter (TL-VSC). Thus, the stability analysis and controller parameters design of the MMC without ignoring internal dynamics must adopt complicated modeling approaches, like the harmonic state-space (HSS) method, which doesn’t have an intuitive insight. Therefore, to simplify the modeling process and give a clear physical meaning, this paper proposes a decoupling method with ac-side impedance shaping by feedforwarding the capacitor voltages to compensate the arm insertion indices, which can also improve the stability of the MMC. Consequently, the ac-side impedance characteristics of the MMC are similar to that of the TL-VSCs, and the stability and controller parameters can be design-oriented by using a simple averaged state-space model. Finally, the effectiveness of the theoretical analysis and correctness of the proposed approach are verified by time-domain simulations in PSCAD/EMTDC.

中文翻译：

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通过使用插入指数补偿调整交流侧阻抗来提高独立 MMC 的稳定性


由于模块化多电平转换器（MMC）中交流侧内部动态的显着耦合，其终端特性与传统的两电平电压源转换器（TL-VSC）有很大不同。因此，在不忽略内部动力学的情况下，MMC的稳定性分析和控制器参数设计必须采用复杂的建模方法，例如谐波状态空间（HSS）方法，其不具有直观的洞察力。因此，为了简化建模过程并给出清晰的物理意义，本文提出了一种具有交流侧阻抗整形的去耦方法，通过前馈电容器电压来补偿臂插入指数，这也可以提高MMC的稳定性。因此，MMC的交流侧阻抗特性与TL-VSC相似，并且可以通过使用简单的平均状态空间模型来设计稳定性和控制器参数。最后，通过PSCAD/EMTDC中的时域仿真验证了理论分析的有效性和所提方法的正确性。