Discrete mode power system stabilisers
The paper presents a comprehensive approach for the design of discrete mode conventional power system stabilisers (PSS) considering a machine infinite bus system, using the ISE technique. Investigations reveal that the sampler and zero order hold (ZOH) need to be modelled for sampling frequencies less than 20 times the Nyquist frequency and that, beyond 20 times the Nyquist frequency, the sampler and ZOH may be neglected from the mathematical model. A comprehensive sensitivity analysis reveals that the discrete mode conventional PSS is quite robust and its nominal optimum parameters need not be reset following ±20% changes in inertia constant H, field open circuit time constant T′d0, line reactance xe, AVR gain KA or loading P and Q from their nominal values.