Robustness of decentralised control systems subject to sensor perturbations

The robustness of decentralised output control designs subject to nonlinear and linear perturbations in the system sensors is studied. Bounds on simultaneously acting nonlinearities are established, and it is shown that it is possible to calculate a sector such that system stability is assured. The suggested approach is not crucially dependent on any particular method for decentralised system design. New relationships are established between perturbation bounds and dominant poles of the nominal closed-loop system, thus helping a designer to select an appropriate degree of stability to attain a robust design. The theory is applied to characterise the robustness properties of a power system example, which employs five DC terminals to damp out inter-area oscillations owing to the AC power system dynamics.