Design of reduced-order observer-based variable structure power system stabiliser for unmeasurable state variables

In the paper, in order to design a simpler and more economical observer-based controller and to solve the problem associated with the unmeasurable state variables in the conventional VSC, a reduced-order (n-m) observer-based variable structure controller (ROOVSC) is proposed and applied to a power system stabiliser (PSS). This ROOVSPSS is obtained by combining the variable structure control (VSC) with a reduced-order observer (ROO): the state estimator by the ROO and the controller by the VSC, which eliminates the need to measure all the state variables in the conventional VSC-PSS. The simulation results are shown by comparison of the ROOPSS with the proposed ROOVSPSS under normal and heavy load operations