Performance-Guaranteed Finite-Time Secondary Control for Islanded AC Microgrids With Time-Varying Disturbances

Abstract

This paper investigates distributed finite-time secondary control of islanded AC microgrids with prescribed performance subject to time-varying disturbances. By specifying the desired performance function, the transient and steady-state performances (including the convergence rate, the maximum overshoot, and the maximum steady-state error) of both the voltage and frequency restoration processes are considered in the design phase. Given the microgrid modeling inaccuracies and load-switching effects, the time-varying disturbances lump unmodeled dynamics, parameter perturbations, and exogenous load disturbances. A novel control scheme, which consists of two main parts, is established. In the first part, reference signal generators are constructed to produce the restoration references in a finite time for each power unit. In the second part, with the observer-based disturbance rejection technique and the prescribed performance control philosophy, performance-guaranteed finite-time secondary controllers are designed such that the finite-time restoration task with the prescribed performance is fulfilled, and the time-varying disturbance rejection is achieved. Rigorous stability analysis and case studies are conducted to verify the correctness and effectiveness of the proposed control scheme.