Analysis of implementation voltage setpoints by synchronous generators in operating points with inverse relation between control variables

Marcos Vinicius Pimentel Teixeira and Ricardo Prada

Analysis of implementation voltage setpoints by synchronous generators in operating points with inverse relation between control variables

Marcos Vinicius Pimentel Teixeira and Ricardo Prada

Pontifical Catholic University of Rio de Janeiro, Brazil

: J Nucl Ene Sci Power Generat Technol

Abstract

Post mortem blackout analysis, which was characterized by voltage drop, suggests that voltage control can aggravate the voltage level. Synchronous generator voltage control is performed by AVR and, in special situations; it may have the opposite effect of its logic of conception. The AVR has no control logic to differentiate direct and inverse relationship between the controlled voltage and the generator excitation voltage. Therefore, if the relationship is inverse, the AVR control may result to be inadequate (opposite to desired), and may lead the system to collapse due to low voltage, for example. Real cases with inverse relationship between controlling and controlled variables occurred in Brazilian system in 1997, 24 and 25 April blackouts. No event or abnormality that would have caused the problem was registered. Full use of available voltage control resources was noticed. This work identifies the causes that lead the generators to operate with inverse relationship between their controlling and controlled variables. The effect of voltage control actions to achieve a new voltage level from operating points that have generators with inverse relationship was studied. The consequence of operation with direct and inverse relationships was analyzed by time domain simulation.