Delay-Dependent Stability Analysis of Multi-Area Load Frequency Control With Enhanced Accuracy and Computation Efficiency

This paper aims at improving calculation accuracy and reducing calculation burden of delay-dependent stability analysis for large-scale multi-area load frequency control (LFC) schemes in traditional and deregulated environments. The special features of the LFC models have been exploited via model reconstruction technique to equivalently transform the original LFC model into a delay-free part and a delay-related part by a transition matrix. The improvement of the calculation efficiency is obtained by decreasing both the number of decision variables and the maximal order of the linear matrix inequalities. Based on the reconstructed model, a novel augmented Lyapunov functional is constructed mainly based on the delay-related part with much lower order and its derivative is bounded with the Wirtinger inequality to establish a stability condition with less conservatism. Case studies are based on two-area LFC systems to verify the effectiveness of proposed stability criteria based on the time-domain indirect method, with a great improvement of the calculation accuracy that can achieve almost accurate delay margins, such as the frequency domain method. Moreover, comparing with the criterion based on the original system model without reconstruction, the calculation efficiency has been greatly improved with the cost of small deduction of accuracy.