基于深度傅里叶变换的调相机启停过程振动问题分析治理

Analysis and Treatment on Vibration of Synchronous Condenser During Start-up and Shutdown Process Based on Depth Fourier Transform

振动问题是同步调相机组常见的问题之一。在某换流站2号调相机冷拖及惰转振动监测过程中,励端支撑系统水平方向的振动速度最高达到12.53 mm/s,超过跳机值11.8 mm/s。为确保后续整套启动及涉网试验安全,提出一种傅里叶变换和频响函数测试相结合的故障诊断方法。首先对旋转机械振动信号进行短时傅里叶变换,得到时频图,接着根据时频图结果开展频响函数测试分析。结果表明,在转子转速大于2700 r/min时,振动二倍频分量具有明显的信号特征,该分量是由励端支撑系统受迫振动频率与固有频率接近引起的。最终,通过将应急油箱支撑与轴承座进行改造分离,改变原有励磁支撑系统固有频率,能够在一定程度上降低冷拖及惰转过程中励端轴承座水平方向振动值。

Vibration is one of the common problems of synchronous condenser set.During vibration monitoring of off-grid driving and running down of one No.2 synchronous condenser at certain converter station,the vibration velocity of the support system on excitation end at the horizontal direction is up to 12.53 mm/s,higher than the trip value of 11.8 mm/s.In order to ensure the safety of subsequent integrated start-up and grid connection related test,a kind fault diagnosis method combining Fourier transform and frequency response function test is proposed.First,short-time Fourier transform is applied to the vibration signal of rotating machinery to obtain time-frequency diagram.Then,frequency response function test and analysis are performed in accordance with the results of time-frequency diagram.The results show that when the rotor speed is greater than 2700 r/min,the double frequency component of the vibration has obvious signal characteristics,which is caused by the proximity of forced vibration frequency to the natural frequency of the support system on excitation end.Finally,the change of natural frequency of original support system on excitation end through the separation of emergency oil tank support and bearing seat can,to a certain extent,reduce the horizontal vibration value of bearing seat on excitation end at horizontal direction in the process of running down and off-grid.