Improvement of low-frequency system stability in 16.7-Hz railway-power grids by multivariable line-converter control in a multiple traction-vehicle scenario

Stability aspects are a major concern in railway-traction applications. It is well-known that low-frequency oscillations occur in 16.7-Hz railway-grids. They can be initiated either by impedance variation or by multiple traction vehicles active in one feeding section. This paper focuses on the emulation of many traction vehicles starting up in the same feeding section and hereby causing instability of the grid. As in practice, all four-quadrant lineside converters are operated close to idle mode. To outline the improvement related to the advanced multivariable control, a comparison to a state-of-the-art PI control is performed. First, the same scenario is done with a conventional PI control showing the typical instability caused. Subsequently, the stability is improved considerably by using an advanced control concept.