As three-phase AC-DC power converters have been extensively employed in DC systems, the grid-interface interaction stability is currently an important concern for the power industry. In particular, the interaction between a flexible traction substation (FTS) and dynamic trains may cause DC system instability. This paper presents a methodology to perform stability investigation of a medium-voltage direct current (MVDC) railway electrification system (RES). A small-signal model in the synchronously rotating dq-frame of an MVDC RES, consisting of a FTS, electric trains and catenary network, has been derived. Results shows that dynamic changes of trains (e.g. number, location, power, controller parameters and capacitor aging), controller parameters of FTSs, AC grid impedance as well as the renewable energy sources connection substantially affect the system stability. This analysis facilitates a design-oriented study. A virtual damping control strategy in the FTS is selected to enhance the system stability. Finally, the theoretical analysis is validated by performing a semi-physical experiment.     «

As three-phase AC-DC power converters have been extensively employed in DC systems, the grid-interface interaction stability is currently an important concern for the power industry. In particular, the interaction between a flexible traction substation (FTS) and dynamic trains may cause DC system instability. This paper presents a methodology to perform stability investigation of a medium-voltage direct current (MVDC) railway electrification system (RES). A small-signal model in the synchronousl...     »