考虑主轴扭转变形的轴系振动模型

针对大型水力发电机组传统上忽略轴系扭转变形的假设可能导致轴系振动分析出现较大偏差的问题,采用Lagrange方法建立轴系振动方程和含轴系扭转效应的转子运动方程,通过定义广义动量,将这2个方程构建为统一形式的一阶微分方程组.以发电机转子上的阻力矩和水轮机转轮上的动力矩为纽带,构建包括水力系统、发电机、励磁、调速系统在内的完整水力机组模拟运行系统,并采用二阶Runge-Kutta法进行仿真计算.计算结果表明,在机组故障扰动条件下,计入轴系的弹性对轴系横向振动的影响不大,主轴扭转刚度对稳定工况下轴的扭转变形影响较大;故障扰动下,发电机转子和水轮机转轮之间的扭转角变化趋势与有功变化趋势基本一致.仿真表明,所建立的轴系扭振模型能反映轴系振动的基本特征,模型是合理的.

Shafting vibration model with torsion deformation in shaft of hydro-turbine generator units

The traditional assumption ignoring torsion deformation in the shafting in hydro-turbine generator units(HTGU)may lead to a large deviation from the actual situation in analyses of shafting vibration. Thus, two equations, i.e. shafting vibration equation and rotor motion equation with torsion effect were established based on the Lagrange method. Further, a unified first-order differential equation was configured with them by defining a generalized momentum. Taking the resistance torque on the generator rotor and the driving torque on the turbine runner as the link, a complete HTGU operating simulation system, including the hydraulic system, generator, excitation controller and governor, was established and solved by making use of the second-order Runge-Kutta method. The calculated results show that the considered torsion effect has a little influence on the lateral vibration of the shafting under unit fault disturbance conditions but has a great impact on the torsion deformation in the shaft under stable operating conditions. Under unit fault disturbance conditions, the variation trend of torsional angle between the generator rotor and the turbine runner is basically consistent with that of active power. These simulations show that the torsion vibration model established in this paper can represent essential features of the shafting vibration, and hence it is reasonable.