Damping and incremental energy in thyristor switching circuits

Thyristor controlled reactors provide controllable inductances in utility power lines and are increasingly used for static var control and flexible AC transmission. The size of a perturbation from a nominal periodic steady state can be measured by its incremental energy. This paper shows that incremental energy of a small perturbation increases when a thyristor switches on and decreases when a thyristor switches off. This observation aids in understanding how perturbations are damped by thyristor switchings and highlights some problems with representing the small signal dynamics of thyristor controlled reactors with impedances