DISCRETE MODE POWER-SYSTEM STABILIZERS

The paper presents a comprehensive approach for the design of discrete mode conventional power system stabilisers (PSS) considering a machin e infinite bus system, using the ISE technique. Investigations reveal that the sampler and zero order hold (ZOH) need to be modelled for sam pling frequencies less than 20 times the Nyquist frequency and that, b eyond 20 times the Nyquist frequency, the sampler and ZOH may be negle cted from the mathematical model. A comprehensive sensitivity analysis reveals that the discrete mode conventional PSS is quite robust and i ts nominal optimum parameters need not be reset following +/-20% chang es in inertia constant H, field open circuit time constant T(d0)', lin e reactance x(e), AVR gain K(A) or loading P and Q from their nominal values.