Improving the robustness of H∞-PSSs using the polynomial approach

This paper proposes a new design procedure of H_∞-PSS (H_∞-optimal PSS) by incorporating high-frequency roll-off into the design using improper weighting function. This design is based on the polynomial approach where the `numerator-denominator´ uncertainty representation is used for practical uncertainty representations. Furthermore, to improve the dynamic and transient stabilities of the control system, the partial pole placement technique is employed to reassign dominant poles at suitable locations in the left-half s-plane. The effectiveness of using Δω (shaft speed) input and ΔP_e (electrical power) input H_∞-PSSs to damp local oscillation modes is also investigated by comparing the performances of these H_∞ -PSSs. Simulation results show that the proposed approach is effective in improving the performance and robustness of the system