Impedance Modeling and Stability Analysis of Triple-Active-Bridge-Converter-Based Renewable-Electricity-Hydrogen-Integrated Metro DC Traction Power System

DC power supply system has been widely applied in metro traction power system. This article presents a novel framework for future metro traction power system (MTPS) with renewable energy, named renewable-electricity-hydrogen-integrated MTPS (RMTPS), to reduce overall energy consumption and carbon emission of the MTPS. The framework and operation modes of RMTPS are first developed, where triple active bridge converter based multiport metro energy router (MMER) is innovatively presented to integrate electricity subsystem, hydrogen subsystem, and MTPS. Then, an impedance modeling method of MMER is developed based on the extra element theorem. It can adaptively obtain terminal impedance characteristics of MMER considering the effect of multidirectional power flow and source/load characteristic variation on other terminals. Furthermore, the stability of RMTPS under different operation modes is investigated based on the developed impedance modeling method. Simulation and experimental results are given to validate the effectiveness of the proposed impedance model and stability analysis for RMTPS. The proposed method can further benefit stability design of MMER in practical application.