Stability analysis of permanent magnet synchronous motors for railway vehicle traction in a sudden line voltage change

In this paper, the stability of the permanent magnet synchronous motors or PMSMs drive system for railway vehicle traction in case of sudden line voltage changes is analysed by applying the root locus method. A seven order steady state equation is derived from the PMSM drive system model equations, including the power feeding circuit from a substation. By applying the steady state model obtained by the model equations, stability is analysed at each speed of the vehicle, q axis current, armature winding resistance of the PMSM and the distance between the vehicle and substation respectively. This analysis has made it clear that the suggested PMSM control system is stable enough to apply the actual vehicle drive system.