ANALYSIS AND CONTROL FOR SUBSYNCHRONOUS RESONANCE PROBLEM.

Dynamic instability, particularly subsynchronous resonance, can often result from using series capacitors in power systems when the series compensation is large and the circuit resistance small. Such a phenomenon is analyzed in the Park coordinates by using the Nyquist criterion. Also some methods are proposed to suppress the subsynchronous resonance oscillation. They are applications of new types of automatic voltage regulators (AVR's) which work as if the resistance of the circuit becomes large and it is confirmed by digital simulations. Furthermore it is shown that these AVR's make the system a little more stable as well for the other types of instability such as mode coupling, which is demonstrated by using the composite system analysis technique.