Power Electronic Devices for Damping Torsional Vibrations
Torsional vibrations and resonance problems with synchronous machines are most frequently encountered in rotor systems with long shafts and large inertias constituting a weakly damped mechanical resonator which exhibits a low resonance frequency. It is impossible to obtain a effective mechanical damping for these torsional vibrations, but by using a power electronics device and an inductive or capacitive energy storage which is connected to the stator winding of the synchronous machine, which produce the same effect as an increased natural damping for oscillation mode in the rotating shaft assembly. This electrical method is applicable to torsional vibration problems in generators and electrical drive systems. The paper presents examples for the successful suppression of torsional resonances in synchronous machines of an isolated power system based on flywheel generators and by three phase fault in the second benchmark model of the IEEE.
Excitation of torsional oscillations in generator shaft lines by plasma feedback control
Abstract The ASDEX Upgrade (AUG) tokamak requires an electrical power up to a few hundred MVA for a time period of 10–20 s. The power and energy is provided by three separate networks based on flywheel generators. In 1999, during a routine check performed on generator EZ3, it was discovered that coupling bolts of the flywheel generator shaft were deformed. Given that the active load of the generator (∼100 MW) in service is well below the design value of the shaft (∼800 MW), the damages may only be explained by a torsional resonance of the shaft line, itself excited by active power transients from the converter loads. A value of 23.6 Hz was calculated for the first eigen-frequency of the shaft line. Frequencies between 10 and 30 Hz have been identified in the spectrum of the load curves. Since torsional shaft oscillations are characterised by very low damping, torsional resonance can become dangerous even for over-dimensioned generator shafts. Therefore, a novel ‘torque’ measurement system was installed. The paper presents results from calculations and measurements showing that devices capable to measure the stress in the shaft line are essential for generator protection in feedback controlled fusion experiments.
CHARACTERISATION OF POWER GENERATION OPTIONS FOR THE 21 ST CENTURY
This report gives an overview of power generation options in the MARKAL model for Western Europe. This model has been used for the evaluation of the economic potential of fusion power in Western Europe in the 21 century. Such an evaluation was part of the so-called SERF programme of the European Union (DG XII). The economic potential of fusion power, as analysed by ECN Policy Studies, is reported in the macro task SE0, which addresses long term scenarios. The present report describes the power generation options included in the model of the Western European energy system, on behalf of macro task E1, cost of fusion. The cost data are expressed as ECU of the year 1995.