大容量电机启动方式对电网的影响

大容量同步电机直接启动时,启动电流很大,会引起电网电压急剧下降。为此,采用自耦变压器降压启动方式启动大型同步电机。建立了含大容量电机的系统潮流计算模型,分析了大容量电机启动方式对110 kV电网和用户变电站供电系统电压的影响。利用动态仿真软件,针对不同系统容量及电机采取不同启动方式进行了电压降落及启动过程的仿真。理论计算与仿真结果表明,大容量同步电机启动时需避开系统小运行方式,验证了自耦变压器降压启动对减小系统压降的可行性。同时,仿真模型可用来确定电机启动时系统的运行方式及降压启动时自耦变压器的抽头。为保证电网电压质量,与直接启动方式相比,大容量电机启动应该采用自耦变压器的降压启动方式,且需选择合适的降压抽头。

Influence of Large-Capacity Motor Starting Modes on Power Grid

The starting current of large-capacity synchronous motor during direct starting is very large, which will cause the voltage of power grid dropping sharply. Therefore, the step-down starting mode of autotransformer was used for the starting of large synchronous motor. The system power flow calculation model with considering large-capacity motor was built, and the influences of the starting mode of large-capacity motor on the 110 kV power grid and the voltage of power supply system in user substation were analyzed. According to different capacities of system and the different starting modes of motor, bus voltage drop and starting process were simulated with using dynamic simulation software. The theoretical calculation and simulation results show that the large-capacity synchronous motor should avoid small mode of system operation during starting, which verifies the feasibility of reducing system voltage drop with using step-down starting mode of autotransformer. In addition, the simulation model can be used to determine the operation mode of the system during motor starting and the autotransformer taps during its step-down starting. In order to ensure the voltage quality of power grid, the step-down starting mode of autotransformer with appropriate taps should be used for the starting of large-capacity motor, compared with the direct starting mode.