The increasing urbanization, population, and travel demand lead to a higher density of trains in subway or tramway lines, which weakens the energy-feeding dc substations of these city transportation means. Under such circumstances, voltage sags in the upstream ac grid, resistive voltage drops in dc feeders, and constant power load (CPL) nature of subway and tramway traction units can lead to momentous fluctuations in the dc-link voltage. To rectify this problem, a supercapacitor-based active stabilizer (SBAS) with a two-mode control strategy (TMCS) is proposed in this article. It is shown that the proposed SBAS exhibits the behavior of a varying capacitance at the bus side. This feature is used in conjunction with the proposed TMCS based on model predictive control (MPC) to improve the stability of the system and to mitigate the variations of the dc-link voltage. The effectiveness of the proposed method is demonstrated by simulation of a typical subway system as well as by a series of experiments on a scaled prototype. The results show that the dc-link voltage drop never exceeds 2% when the proposed SBAS is used. In addition, the real-time feasibility of the proposed MPC-based TMCS is demonstrated by real-time hardware-in-the-loop (HIL) experiments.

中文翻译：

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使用基于超级电容器的有源稳定器和模型预测控制的直流牵引系统的动态稳定

不断增长的城市化、人口和出行需求导致地铁或有轨电车线路中的列车密度更高，这削弱了这些城市交通工具的能量馈送直流变电站。在这种情况下，上游交流电网的电压骤降、直流馈线中的电阻性电压降以及地铁和有轨电车牵引装置的恒功率负载 (CPL) 特性都会导致直流链路电压发生重大波动。为了解决这个问题，本文提出了一种具有双模式控制策略 (TMCS) 的基于超级电容器的主动稳定器 (SBAS)。结果表明，所提出的 SBAS 表现出总线侧电容变化的行为。此功能与基于模型预测控制 (MPC) 的拟议 TMCS 结合使用，以提高系统的稳定性并减轻直流链路电压的变化。通过对典型地铁系统的模拟以及在缩放原型上进行的一系列实验，证明了所提出方法的有效性。结果表明，当使用建议的 SBAS 时，直流母线电压降从未超过 2%。此外，实时硬件在环 (HIL) 实验证明了所提出的基于 MPC 的 TMCS 的实时可行性。