Analysis of dynamic load behavior for electrified mass rapid transit systems

This paper investigates the dynamic load flow behavior of an electrified mass rapid transit (MRT) system. Because the power consumption of an MRT system varies with train operation mode and system route gradient, curvature, etc., the motion equation of train sets has been applied to find the mechanical power required for train operation. The electrical input power to the car borne VVVF inverters for the driving of induction motors are solved by the simulation of power electronics. The impedance matrix of the DC power network is then modified for each study snapshot based on the train location and the corresponding resistance change of the conducting 3rd rail and train running rail. The DC and AC load flow analyses have been performed for a practical MRT line in Taipei by considering the operation timetable and actual ridership to demonstrate the effectiveness of the proposed computer simulation methodology. The power consumption of the MRT is solved and the energy conservation by electric regenerative braking when the train set approaches the next station is also determined. The variation of traction transformer loading factors with train operation are calculated for the evaluation of power system operation efficiency. It is concluded that the power flow analysis does provide a very useful tool for the proper capacity planning of traction substations during the design stage of an MRT system.