A robust H2/H∞ control strategy based on uncertainty of polytope and reduction of conservatism

Due to only utilizing one common Lyapunov matrix there was a certain conservatism in traditional H2/H∞ control method, in the mean time the uncertainty caused by unknown system structure and change of operation point was not taken into account in traditional method. In allusion to these defects a control strategy of inter-area oscillation, which considered both reduction of conservatism and uncertainty of polytope, was proposed. Firstly, the Lyapunov matrix in H2/H∞ control theory was separated from system matrix; then Lyapunov matrices for H2 control and H∞ control, which could make the constraints apices of the polytope tenable, were derived respectively; Finally the input vectors of feedback control, which could satisfy the uncertainty of polytope, was attained. Simulation results of IEEE 2-area 4-machine system showed that comparing with the H2/H∞ control method, in which the conservatism was not reduced and the uncertainty of polytope was not considered, the proposed method possessed stronger robustness and could suppress inter-area oscillation more effectively.