Effect of steam pressure fluctuation in turbine steam pipe on stability of power system

Low frequency oscillation is one of the most important dynamic stability problems in power system, which has great effects on the security and stability of power system. In recent years, low frequency oscillation phenomenon occurred for many times in China. A new fact is introduced which may lead to low frequency power oscillation of power system. In a power plant experiment, it was found that the quick operation of governing system would cause the pressure oscillation in turbine steam inlet pipeline. The frequency of pressure oscillation depends heavily on the structure and size of steam inlet pipeline. It is found that the frequency of the steam pressure continuous fluctuation is in the range of 0.1~10 Hz, which cover the frequency of power system low frequency oscillation. The interaction between the steam pressure and the power system may be occurred. On the basis of single machine infinite bus model, the process of quick operation of steam turbine governing valve and the effect of steam pressure fluctuation in turbine steam pipe on power system dynamic stability was researched through the simulation. The simulation results indicate that the quick operation of steam turbine governing valve may lead to power system low frequency oscillation, if the natural frequency of pressure fluctuation caused by governing valve quick operation is equal or close to the power system natural oscillation frequency. The conclusion can provide reference to research into the causes of power system low frequency oscillations.