Abstract:

The power supply system of metro light rail, applying DC traction and three-level inverter technology, is of strong volatility and abundant system harmonic, tending to affect the safe and stable operation of the power system. In the paper, the effects of the power supply system of metro light rail on the power quality of the public electricity grid are investigated under various operation conditions. According to the actual parameters of the locomotive, the tractive power supply system and the public electricity grid, a complete model including traction motor and public power system is established and verified by the on-site measurement data. Based on the model, it is concluded that the harmonic injection in the public electricity grid by the power supply system is the characteristic harmonics induced by the 24-pulse rectification and inverter working, however, both the negative sequence and the voltage flicker value meet the national standards. By changing the operational status and numbers of the train, the total harmonics can even reach 17% at the startup of traction motor. With the increasing numbers of the train, though the voltage decreases sharply, it accords with the standard.