Gate-turn-off thyristors provide new level of power-flow control
The availability of high-power, gate-turn-off (GTO) thyristors has made possible the development of a new class of solid-state devices that promise an unprecedented degree of control over the flow of power in the nation`s network. The first of these, a static compensator known as Statcom, which offers dynamic control over the flow of VArs into, or out of, the network, was unveiled last month at the Tennessee Valley Authority`s (TVA) Sullivan substation in eastern Tennessee. The principal element of the Statcom is a voltage-sourced inverter that converts dc voltage at its input terminals into a 3-phase alternating output voltage. To eliminate the quasi square wave that a single inverter would generate - along with unacceptable harmonics - the Statcom uses many such inverters, appropriately phase-shifted, and combines their outputs through electromagnetic linkages to produce a nearly sinusoidal output waveform. By numerous voltage additions and subtractions, eight inverters used in the Statcom generate a 48-pulse, nearly sinusoidal output waveform. The GTO-based inverters and electronic feedback control give the Statcom a dynamic performance far exceeding that of other reactive power compensators. In fact, the device can transition from full rated capacitive to full-rated VArs in approximately one-quarter cycle. Nominal rating of each inverter is 12.5 MVA. 12 figs.
- OSTI ID:
- 171393
- Journal Information:
- Electrical World, Journal Name: Electrical World Journal Issue: 12 Vol. 209; ISSN 0013-4457; ISSN ELWOA3
- Country of Publication:
- United States
- Language:
- English
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