二重シールドをもつ超電導同期発電機の電力系統内特性とその改善法

抄録

So as to increase both of the shielding effect for protecting the superconducting field winding against asynchronously rotated armature-reactive magnetic fields and the damping effect for rotor swings in transients, the double electromagnetic shielding scheme has been lately established in superconducting alternators.
One of elctromagnetic features, which stem from the adoption of a shielding system with relatively large time constant and the superconducting field circuit with exceptionally large time constant, is that an excitation voltage ceiling should be enormously raised in the case of typical field forcing control to provide supplementary damping force of the rotor, to ensure a good dynamic voltage regulation, and then to guarantee a power system stability. Nevertheless, in such a superconducting system, a high value of field current variation could ont be acceptable from points of the limitation of a critical magnetic field changing rate, a temperature rise caused by ac losses in superconductors and other cryogenic rotor components, and so on. Even though a great deal of field forcing might be acceptable, only very little improvement could be achieved in the dynamic performance.
Hence it might be of necessity that new alternative contol schemes have been proposed, for instance, a shield winding control and a static reactive power compensator control connected at the terminal of the generator, instead of the conventional field forcing control.
The paper has reviewed such new control schemes besides the conventional typical control, and discussed their control performances based on computer simulations which the author has done up to now.