Torsional Oscillations and Damageability of the Rotor Shaft of the Turbogenerators Fitted with Automatic Regulated Excitation

Abstract

The assessment of damage to the rotor shaft of the turbine-generator due to resonant interaction between generator and exciter, due to automatic excitation regulator (ARV) by mathematical modeling. The thyristor system of independent excitation is used in the work. The simulated circuit includes a turbogenerator with a block transformer, a power line, a synchronous generator and a gate-controlled exciter Converter. When modeling the electrical part, an approach is used from the position of its own coordinates, which provides maximum methodological consistency of the models of the listed devices and allows directly reproducing resonant phenomena at frequencies of torsional vibrations with the determination of instantaneous values of currents, voltages and electromagnetic moments of the turbo generator and exciter. The mechanical system is presented taking into account the exciter as a six-mass system. ARV is introduced into the mathematical model by means of transfer functions with corresponding coefficients and time constants. The control system of the gate Converter of the exciter is represented in the model by a generator of linearly increasing signals, a body for comparing these signals with the signal from the ARV and a control pulse generator. The deformation criterion for soft and hard loads in the zone of low-cycle fatigue and the force criterion in the zone of multi-cycle fatigue were used to assess the damage. A comparative quantitative assessment of the damage to the generator rotor shaft under resonant interaction at all subsynchronous frequencies of torsional vibrations and in near-resonant modes is given. The influence of attenuation of electromagnetic transients and damping of torsional vibrations on the damage values is analyzed.