Adjustable Predefined-Time Sliding-Mode Frequency Control of Microgrids with Hybrid Energy Storage Systems and Cyberattacks

In power grids, the introduction of renewable energy may affect frequency stability. Therefore, this paper considers adjustable predefined-time sliding-mode frequency control of microgrids with hybrid energy storage systems (HESSs) and cyberattacks. First, by analyzing dynamics of the ultracapacitors, batteries and cyberattacks, models of the HESS and aperiodic DoS attacks are established. To compensate the disturbances induced by renewable energy, an adjustable predefined-time observer (APTO) is designed, which combines adaptive laws such that the observation error converges to the specified boundary with a predefined time that is regulated by a flexible scalar. Based on the observer, an integral sliding surface is designed. Then, by introducing a switched system, the stability of the sliding-mode dynamics is analyzed. Moreover, to guarantee reachability of the sliding surface, a predefined-time sliding-mode controller is designed. Compared with the existing results, the proposed controller is independent of the initial states. At last, the two-area microgrids are used to illustrate the effectiveness of the designed controller. Compared with SMC and FTSMC, the frequency deviation is reduced by 6.79% and 4.78% and the convergence time is reduced by 31.6% and 13.3%. It is shown that the proposed controller achieves fast convergence and strong robustness.