Michael J. Gibbard

The object of this paper is to demonstrate the performance of a Ramp-Rejecting electric Power Prefilter (RRPP), which is a modification of the Conventional Electric Power Prefilter (CPP) for a speed-PSS. The RRPP can markedly reduce the undesirable swings in generator voltage and reactive power output due to ramping of turbine power. Like the Dual Input Prefilter (DIP) of the integral-of-accelerating-power (IAP) PSS the RRPP (i) significantly attenuates the torsional modes; and (ii) enhances modal damping. Significantly, the RRPP does not require an externally-estimated rotor-speed input signal - which is an important requirement of the DIP. For example, using generator terminal variables for the DIP it is difficult to accurately estimate a rotor-speed input that covers a wide range of operating conditions and modal frequencies.

This paper describes a nonlinear control strategy for the design of a controller (stabiliser) for a synchronous generator. It is first shown that a nonlinear model, which is derived from the equations of the generator and power system, describes the nonlinear relationship between the electric power output and the excitation control input and, hence, inherently tracks the system dynamics due to changes in the system operating point. Based on the nonlinear model, a nonlinear controller which incorporates the nonlinearities of the power system into the design of the control law is proposed. Simulation studies on the power system reveal that its damping performance due to the nonlinear controller is better than that due to a corresponding adaptive linear device discussed in the literature.

© 2005 IEEE.This paper summarizes the work done by the Task Force on Assessing the Need to Include Higher Order Terms for Small-Signal (Modal) Analysis. This Task Force was created by the Power System Dynamic Performance Committee to investigate the need to include higher order terms for small signal (modal) analysis. The focus of the work reported here is on establishing and documenting the practical significance of these terms in stability analysis using the method of Normal Forms. Special emphasis was placed on determining and describing conditions when higher order terms need to be included to accurately describe modal interactions. Test cases were developed on a standard test system to demonstrate the application of appropriate indices to detect the occurrence of nonlinear interaction and hence the need for higher order terms in stability analyzes. The use of the higher order terms in the site selection for a damping controller is also documented.Sanchez-Gasca, J.J. Vittal, V. Gibbard, M.J. Messina, A.R. Vowles, D.J. Liu, S. Annakkage, U.D