A Novel Inverter Control Strategy with Power Decoupling for Microgrid Operations in Grid-Connected and Islanded Modes

TL;DR

This paper presents a unified inverter control strategy with power decoupling that enhances microgrid stability and performance in both grid-connected and islanded modes by integrating virtual inertia, damping, and coupling compensation.

Contribution

It introduces a novel unified dynamic power coupling model that combines droop and VSG controls, enabling adaptable and stable microgrid operation across modes.

Findings

Effective control of active power in both modes

Enhanced stability with virtual inertia and damping

Validated through comprehensive simulations

Abstract

Grid-forming, particularly those utilizing droop control and virtual synchronous generators (VSG), can actively regulate the frequency and voltage of microgrid systems, exhibiting dynamic characteristics akin to those of synchronous generators. Although droop control and VSG control each have distinct benefits, neither can fully meet the diverse, dynamic needs of both grid-connected (GC) and islanded (IS) modes. Additionally, the coupling between active and reactive power can negatively impact microgrids' dynamic performance and stability. To solve these problems, this paper introduces a unified dynamic power coupling (UDC) model. This model's active power control loop can be tailored to meet diverse requirements. By implementing a well-designed control loop, the system can harness the advantages of both droop control and VSG control. In islanded mode, the proposed model can provide virtual inertia and damping properties, while in grid-connected mode, the inverter's active power output can follow the changed references without significant overshoot or oscillation. Furthermore, the model incorporates coupling compensation and virtual impedance based on a relative gain array in the frequency domain to facilitate quantitative analysis of power coupling characteristics. This paper outlines a distinct design process for the unified model. Finally, the proposed control method has been validated through simulation.