A new method of tuning power system stabilisers

A numerical optimization method using an H_∞ norm as the objective function was presented to tune a fixed structure power system stabiliser (PSS), thereby achieving a robust PSS (RPSS), while still maintaining the existing structure. A damping constraint was included to achieve the required damping, since optimal H_∞ control does not improve damping. To illustrate the method, a three machine-nine-bus system and a second order PSS were chosen. The RPSS was shown to be more robust than conventional PSS and improve the overall response of the system and not only the local mode of one generator. The RPSS was shown to be more practical than an optimal H_∞, PSS. In summary, the tuning method presented in this paper has the following advantages over classical design techniques: better overall damping and robustness, no restriction on the number of parameters, and no fixed relationship between parameters. Compared with optimal H_∞ design methods, the method presented in this paper has the following advantages: PSS are of a pre-determined order and structure, overall damping is better, and no model reduction is required to obtain lower order PSS