Coordinated control analysis of under-excitation limiter

Inappropriate parameter tuning of under excitation limiter (UEL) will weaken system damping, and even lead to system instability, which is attributed to two reasons according to the theoretical analysis. Firstly, UEL with inappropriate parameters provides a negative damping torque and, secondly frequency bond of UEL is incoordinate with that of power system stabilizer (PSS). Further, a single-machine infinity bus system based on PSS/E and MATLAB is established and the conclusion of theoretical analysis is verified. Result shows that, if UEL provides negative damping, the lower the frequency bond of UEL action gets and the smaller the slope of UEL stability curve is, the better time domain system dynamic response is.