Transient voltage and current stresses are essential for the design and protection of multi-terminal DC (MTDC) transmission systems, especially under the short-term dynamics after severe grid faults. In this paper, we propose a discrete-time model for the modular multilevel converter based MTDC (MMC-MTDC) system considering the DC-side disturbances in the system. Based on the piecewise linear modeling, the state variables such as the transient voltage on the sub-module (SM), arm current, etc., can be calculated analytically for the critical short term (within 10 ms) after the severe DC fault while the system protection is yet to be activated. Parameter sensitivity analysis is also performed to give a better system design guideline. The estimation results are validated by detailed electromagnetic (EMT) circuit simulations and the scaled-down experimental laboratory prototype.

中文翻译：

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基于离散时间分析的 MMC-MTDC 系统瞬态电压和电流应力估计

瞬态电压和电流应力对于多端直流 (MTDC) 输电系统的设计和保护至关重要，尤其是在严重电网故障后的短期动态下。在本文中，我们为基于模块化多电平转换器的 MTDC (MMC-MTDC) 系统提出了一种考虑系统中直流侧扰动的离散时间模型。基于分段线性建模，子模块上的瞬态电压（SM）、臂电流等状态变量可以在严重直流故障后的临界短期（10 ms内）进行解析计算，同时系统保护尚未激活。还执行参数敏感性分析以提供更好的系统设计指南。