Continuous Abstraction Modelling and Control of Grid-Forming Inverters
Elnaz Firouzmand, Farhad Farokhi, Iman Sharifi, Heidar Ali Talebi · 2024
This paper presents the development of a continuous abstract model and hierarchical control of grid-forming inverters (GFMIs) under external disturbances and limited access to system states. Power inverters, particularly the GFMIs, do not have the same built-in controls or inherent physical inertia as standard synchronous machines. In addition, these systems are described by linear dynamics with a high-dimensional state space. Thus, the stability analysis and control of large microgrids that use modern power inverters are computationally complex. In this regard, developing an accurate reduced-order model, along with a systematic control structure, can alleviate this challenge. We present an approach for modelling GFMIs using a continuous abstract model as a reduced-order model. This model closely approximates the output of the GFMI with a priori known upper bound and can accurately capture the slow and fast modes of the concrete GFMI as intended by the designer. Furthermore, a hierarchical control structure is introduced to control the GFMI under external disturbances and limited access to its device and control level states. The applicability of the proposed idea is shown via simulation for a GFMI.