轻轨供电系统采用直流牵引和三电平逆变技术，具有波动性强、系统谐波含量丰富等特点，有可能威胁到电力系统的安全稳定运行。研究了轻轨供电系统在不同运行状态下对公共电网电能质量的影响规律。依据机车、牵引供电系统和公共电网的实际参数，搭建包括公共电网在内的城市轨道交通牵引供电系统整体仿真模型，并通过实际的现场谐波测试数据加以验证。以此模型为平台，得出该供电系统向公共电网注入谐波主要是24脉波整流导致的特征谐波（23、25次）和逆变器工作所导致的特征谐波（11、13次），而负序和电压闪变值都符合国家标准。通过改变运行列车的运行状态和数量，在列车启动瞬间其瞬时谐波含量最高可达到17%；随着列车数量的增加，电压下降明显，但仍在标准允许范围内。

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.