A unified limited power reference generation for inverters under sinusoidal imbalance conditions

Abstract

This paper outlines a comprehensive current limiting approach for grid-following inverters operating under sinusoidal unbalanced conditions. The framework addresses the complexities of aligning various control objectives, handling symmetrical and asymmetrical grid faults, and ensuring adherence to grid connection requirements. This paper begins by presenting a unified control architecture that combines different control methods, including power-characteristic- and voltage-oriented approaches, along with their sub-techniques, such as injecting balanced current and constant active/reactive powers, into a single, cohesive framework. This unified control architecture enables the implementation of a comprehensive current limiting technique that can adapt to various operational conditions. Accordingly, a unified current limiting scheme is developed, which calculates the limited active and reactive power levels by considering the interplay between the unbalanced currents, the reference powers, and the maximum allowable current of the inverter. Extensive time-domain simulations, numerical analyses, and experimental tests have validated the effectiveness of the proposed strategy in accurately limiting output currents during severe asymmetrical and symmetrical short-circuit faults.