Circuit arrangement for attenuation of power oscillations in networks

A circuit arrangement for supplying a signal to the exciter of at least one synchronous machine in order to attenuate power oscillations in a network to which the synchronous machine is coupled comprising:

• (a) first and second vector identifiers having as an input detected power oscillations in the system, each vector identifier providing a direct and a phase-shifted output, each designed for a different frequency;
• (b) first, second, third and fourth matching means receiving as inputs respectively, the direct output of said first vector identifier, the phase-shifted output of said first vector identifier, the direct output of said second vector identifier and the phase-shifted output of said second vector identifier;
• (c) first and second summing junctions, said first summing junction having as inputs the output of said first and fourth matching means and the second summing junction having as inputs the outputs of said second and third matching means;
• (d) fifth and sixth matching means having as inputs respectively, the outputs of said first and second summing junctions;
• and
• (e) third summing junction having as inputs the outputs of said fifth and sixth matching means and providing at its output a total signal which, over a selectable frequency range, varies in a mathematically positive sense with increasing oscillation frequency whereby said signal can be supplied to the exciter of a synchronous machine in order to damp power oscillations in the network.