Decoupling negative damping signals in a power system throughdynamic gain reduction measures

摘要

Low frequency oscillations occurring in a power system can beaccentuated in generators through a feedback loop which connects theoutput of the system to the summing junction of the automatic voltageregulator (AVR) where the power system stabilizer (PSS) is alsoconnected. A method of decoupling these oscillations withoutcompromising the benevolent effects of other control loops in thatsystem is presented. A notch filter, located in the forward path of thenegative damping signal, provides the necessary dynamic gain reduction(DGR) for switching off the detrimental signals. Relevant frequencydomain analysis of the closed loop transfer function of a typical powersystem is provided which reflects the effect of tie-line disturbances onpower angle oscillations. This leads to a restructuring of the transferblocks in the system and the design of a DGR block that allows thedecoupling of the negative damping signals. Additional insight into theeffect of negative damping signals and their subsequent decoupling isprovided through the examination of loop and transfer blocksignals