Optimal Control Design for Load Frequency Control with Network-induced Delays

Abstract

In recent years, microgrids develop rapidly due to the superiority of reliability and flexibility. Load frequency control (LFC), as a vital role in microgrids, can maintain the stability of the microgrid and ensure that the exchange power on the tie line between interconnected power systems remains at the desired value. In the LFC system, wireless communication is the key factor to make the system more efficient and concise while it gives rise to delays in the meantime. In this paper, an optimal LFC algorithm is proposed in the presence of the network-induced delay. First, the LFC system is analyzed, and then the discrete-time system model is established. Then, the optimal LFC problem is formulated using a quadratic cost function with the objective of minimizing the deviations of frequency. The optimal close-loop control strategy is solved in an iterative manner by using a backward recursion which can be divided into two steps. In particular, the optimal control gain can be iteratively derived at off-line step, and then the control strategy can be calculated at on-line step. Finally, the performance and stability of proposed optimal LFC algorithm are verified by numerical simulations to highlight its superiority compared with the existing algorithms.