LMI based robust load frequency control for time delayed power system via delay margin estimation

Abstract

The employment of communication channels inevitably result in the advent of time delays in load frequency control (LFC) schemes. The existence of such time delays exerts potential threats on the stability of power systems. This paper aims to study a three-area time delayed power system and propose a linear matrix inequality (LMI) based robust LFC scheme with delay margin estimation. Analytic form of the delay margin is subsequently provided. Following that, LMI based robust controller design procedure is proposed based on delay margin estimation, wherein the robust performance index (RPI) is introduced. The robust controller gains are ultimately obtained with the estimated delay margin and a binary search technique which aims to find the minimum value of RPI. Simulations are conducted to evaluate performance of the proposed scheme: the effectiveness of the DME process is verified under an ideal power system condition; a second simulation incorporating the effects on GRC and GDB is conducted to further validate the rightness of DMC; parameter perturbations are considered in the next simulation; a comparative study which compares the proposed approach with other three existing methods is initialized in the fourth simulation test; at last, the impact of a micro grid comprises wind and solar energy generation units is incorporated to test the performance of the novel method. The simulation results indicate that the delay margin estimation procedure is effective and the proposed control scheme is robust and has superior performance over conventional LMI based robust control schemes.