Thyristor converter-modulated impedance under unbalanced system conditions

The paper presents the use of a digital simulation program to assess the concept of modulated impedance under unbalanced system conditions, and the relationship between apparant system impedance Z_ac and thyristor converter rectifier firing delay angle α. Modulated impedance/reactance applications in power systems and machines include network stability enhancement tools, VAR shunt compensation, subsynchronous resonance damping, motor drive speed control, and starting of large slip-ring induction motors. The digital simulation results were validated by laboratory testing.