Abstract: An Inverter-Controller Series Compensator (ICSC) has a reactive impedance element connected in series with the line of an ac transmission system and an inverter connected in parallel with the reactive impedance element to control the voltage across, and therefore the current through, the reactive impedance element to provide a continuously adjustable series reactance for power flow control, series voltage regulation, oscillation damping and stability enhancement, as needed. By providing the inverter with a source/sink of real power, the ICSC is further capable of adjusting series impedance. The reactive impedance element can be either a capacitive element or an inductive element depending upon whether there is a need for capacitive or inductive compensation.

Abstract: Apparatus for providing reactive compensation and positive real power compensation in an ac electric power transmission system, utilizes a solid state inverter to inject a series compensation voltage into the transmission line at a controllable magnitude and a controllable phase angle between + or -90 electrical degrees relative to transmission line current. The positive real power needed by the inverter is drawn from the transmission line by a rectifier shunt connected to the line.

Abstract: A dynamic stabilizer of the type which is utilized to compensate or stabilize the effect of subsynchronous resonance oscillations in a turbine generator system is taught. Silicon controlled rectifiers are connected in series with inductors between the lines of the electrical system. The silicon controlled rectifiers may be maintained at two quiescent conduction intervals of 90.degree. and 135.degree. depending upon the peak value of rotor oscillation. If the peak value of rotor oscillation is sufficiently small the lower conduction interval of 90.degree. is utilized as this is sufficient to stabilize low level oscillations. Furthermore, it has great advantage in the fact that the losses represented by 90.degree. quiescent conduction interval are relatively small when compared with the larger quiescent conduction interval.

Abstract: This concerns a compensator for electrical lines fed by a turbine-generator. The mechanical properties of the turbine-generator are such that modulation of the terminal voltage is possible due to subsynchronous mechanical torsional oscillations. If the carrier frequency or synchronous frequency of the generator minus the torsional oscillation frequency is equal to the resonant frequency of the electrical line driven thereby, a relatively large side band current may flow in the electrical line at the resonant frequency. The effect of this current may feedback through the air gap of the generator to increase the torsional oscillation. A boot strapping effect between the electrical properties of the line and the torsional oscillation may thus result which could ultimately end in shaft breakage.

Abstract: This invention concerns apparatus for reliably estimating the strain on an inaccessible portion of a shaft of a turbine generator system which is susceptible to torsional oscillation. The strain is continuously predicted on a real time basis as a function of the modal analysis parameters of the shaft. Furthermore, system torque is detected electrically at the output of the generator. This signal along with signals representative of shaft angular velocity at the easily accessible ends thereof is provided to the modal analysis means as inputs. The provision of these latter system data allow for the elimination of an equal number of unknowns in the modal analysis representation, thus reducing the complexity of the analyzing system and increasing the reliability.