电力电子装备在电力系统中的广泛应用使得现代电力系统动态行为发生了显著变化，基于电网换相整流器的高压直流输电（LCC-HVDC）作为电力系统重要的组成部分，对电力系统的安全稳定运行具有重要影响。由于LCC-HVDC开关过程呈现断续时变特征，且开关频率与电磁尺度时间常数相当，因此断续时变开关过程的动态特性描述是研究LCC-HVDC电磁尺度动态稳定问题的关键。为此，该文提出了适用于计及开关过程的LCC-HVDC电磁尺度动态稳定分析的小信号模型。首先讨论了LCC-HVDC原始关系及其非线性断续周期时变特征，指出基本问题和挑战；然后基于线性周期时变理论建立了LCC-HVDC电磁尺度下的小信号模型。最后，通过与现有不考虑时变开关过程模型的对比分析，探究了开关过程对系统稳定性的影响，并通过时域仿真验证了分析的正确性。
The wide application of power electronic equipment in power systems has caused significant changes in the dynamic behavior of modern power systems. As an important power system component, line commutated converter based high voltage direct current (LCC-HVDC) systems have an important impact on the safe, stable operation of power systems. Since the switching process in LCC-HVDC systems has intermittent time-varying characteristics and the switching frequency is equivalent to the electromagnetic timescale constant, these intermittent time-varying switching characteristics are the key to the stability of LCC-HVDC systems. This paper presents an electromagnetic timescale, small-signal model for LCC-HVDC systems that includes the switching process with a stability analysis. The model includes the nonlinear characteristics and the inherent periodic time-varying characteristics of LCC-HVDC systems for modeling the key challenges in the control system. Then, linear time-periodic theory is used to develop an electromagnetic timescale, small-signal model of the LCC-HVDC system. Finally, this model is compared with an existing model that does not consider the time-varying characteristics of the switching process to show the influence of the switching on the system stability with the results verified by time-domain simulations.
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