Abstract: Subsynchronous oscillations and DC offset in an electrical power system are dampened by measuring the half-cycle period of current or voltage line waves, comparing the measured half-cycle time periods to a desired half-cycle time period and dissipating the line waves in measured half-cycle time periods which are longer than the desired half-cycle time period. Damping apparatus includes a reactance connected in a power line with selectively bi-directional conductors in parallel with the reactance whereby the reactance can be shorted. Alternatively, the selectively bi-directional conductors can connect a power line to ground or neutral when half-cycle time periods exceed a desired half-cycle time period.

Abstract: In an alternating current electric power system of the type subject to rapid load voltage regulation as a result of variations in reactive load current, reactive load current compensation is provided by fixed capacitors and inductors in parallel with the load. The inductors are in series with static switches which are phase controlled to continuously maintain the net reactive compensating current substantially equal and opposite to the reactive components of load currents. Compensation control determines firing time of thyristor switches in accordance with the magnitude of reactive load current. In one embodiment, a signal representative of the condition of the reactive load current is provided with a positive phase shift correction to compensate for a negative phase shift which is provided by the thyristor switching technique.

Abstract: A control circuit of a reactive power compensation apparatus which comprises a reactor and a capacitor are connected in parallel between a power source and a load to perform phase control of current passing through the reactor by a control switching element such as thyristor. The control circuit comprises a device for detecting instantaneous value of load current at a predetermined phase of the power voltage, a multiplier, a subtractor and a divider and a device for generating gate pulse in comparison of the output signal of the divider with the rating function generated in synchronizing to the peak phase of the power voltage.