Modelling the steady-state of secondary control in islanded AC microgrids

Abstract

The secondary control is applied in islanded Microgrids (MGs), after the primary control, in order to restore the voltages and frequency to specified values. Although existing power flow methods can accurately calculate the power flow of primary and tertiary control of islanded MGs, they present considerable limitations in the modelling of secondary control. The main challenge is that secondary controllers consist of integral parts, which under communication failures, could integrate functions with different integral histories, and thus, can imply non-uniform power production of distributed generators (DGs). This paper proposes a power flow method for calculating, accurately, the steady-state of secondary control in islanded MGs. The method has four distinct features: a) generalized implementation in several communication strategies e.g., centralized, decentralized, consensus, distributed averaging, b) precise simulation of communication links and proportional-integral (PI) controllers, c) low computation time, and d) accurate three-phase network representation. Simulations were executed to validate the proposed method and highlight the importance of modelling, precisely, the secondary control in islanded MGs.