On intrinsic robust versus adaptive power system stabilisers

Increasing use of AVR (automatic voltage regulators) on generating units to improve the transient stability of power transfer in an interconnected power system has resulted in poor dynamic stability. The low frequency oscillations in the range of 0.5 to 2.5 Hz build up to such proportions that in practice these lead to shaft failure. Power system stabilisers based on shaft speed sensing have been recommended but various others signals like power or bus frequency have also been tried. However, the gain setting of the stabiliser loop is not unique and depends on the system characteristics and the loading pattern. The solution is sought on the basis of parameter identification and tracking and an adaptive gain setting. The authors discuss the necessity of robust controller design rather than an adaptive power system stabiliser using advanced linear control theory. The possibility of a digital controller has also been explored