Method and means for damping subsynchronous oscillations and DC offset in an AC power system
AssigneeElectric Power Research Institute, Inc.
InventorNarain G. Hingorani
Life of this patent
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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 bidirectional 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.
Claims12
The method of damping subsynchronous oscillations and DC offset in an AC power system comprising the steps of
- measuring the half-cycle time period of line waves in said power system,
- comparing said measured half-cycle to a desired half-cycle time period, and
- dissipating said line waves in resistive means in measured half-cycles which are longer than said desired half-cycle time period to the extent said measured half-cycles exceed said desired half-cycle time period.
Apparatus for damping subsynchronous oscillations and DC current offset in an AC power line comprising
- a capacitor serially connected in said power line,
- circuit means connected in parallel with said capacitor and including a resistor, a selectively bi-directional conduction means including first and second thyristors connected in parallel and in opposite polarity, and means serially connecting said selectively bi-directional conduction means with said resistor, and
- means for triggering said selectively bi-directional conduction means in response to half-cycle time period of voltage across said capacitor exceeding a preselected time period whereby power is dissipated in said resistor beginning at the end of said preselected time period and ending at the end of said half-cycle time period.
Apparatus as defined by claim 9 wherein said circuit means further includes a non-linear resistor connected in parallel with said bi-directional conduction means.
Apparatus for damping subsynchronous oscillations and DC voltage offset in an AC power line comprising capacitor means for connecting a power line in series to a circuit neutral connection, circuit means in parallel with said capacitor means and including resistance means and a serially connected selectively bi-directional conduction means, and means for triggering said selectively bi-directional conduction means in response to half-cycle time periods of voltage waves on said power line exceeding a preselected time period thereby bypassing said capacitor means.
Dependencies are inferred from the claim text.