Adaptive Security Secondary Control for Microgrid in Prescribed Performance

Abstract

This paper studies the prescribed performance adaptive secondary control problem of the microgrid (MG) under denial-of-service (DoS) attacks. By considering parameter uncertainties and voltage losses, a more practical MG model is established with an uncertain control gain and an unknown nonlinear function. Then, an ingenious fuzzy estimator without the uncertain control gain term is proposed to estimate the unmeasurable state variables and reduce the impact of DoS attacks simultaneously. At the same time, a new estimation error is defined to simplify the derivation process of the estimate error system. To ensure that the voltage fluctuations caused by DoS attacks and load perturbations still satisfy the asymmetric constraints, a novel asymmetric performance function with consideration of the allowable voltage deviation criterion is constructed. In addition, to reduce the controller design complexity, the voltage restoration synchronization error with boundary constraint is transformed into the unconstrained performance error. Further, combining with the designed fuzzy state estimator and the performance transformation error, an adaptive security controller is proposed by using the backstepping technology to ensure that the voltage restoration synchronization error can enter the prescribed asymmetric convergence region within the predefined finite time. Finally, the effectiveness of the designed security controller is verified by two simulations with comparisons. Note to Practitioners—In this paper, a more practical MG system is modeled by considering the factors of the circuit component aging, faults, source voltage disturbances, and voltage losses. Next, the prescribed performance voltage restoration problem under DoS attacks is solved. Since DoS attacks and load perturbations have a great impact on the voltage control, a prescribed performance security control method is proposed to ensure that the transient voltage restoration synchronization error remains strictly within the prescribed region. Additionally, both the convergence time and the asymmetric voltage fluctuation region are predefined by practitioners. This enables practitioners to obtain more specific stabilization time and satisfactory transient performance in the MG. The rationality of the theoretical analysis results is verified by simulation experiments.