Power Coupling Index (PCI) Oriented Stability Analysis and Interaction Control Design for Inverter-Based Microgrid Under Complex Line Impedance

In the distributed power grid with renewable power generation that works based on converters, the grid-forming inverter is a crucial component. Under different line impedance, a given control-based inverter would be instability due to the complex power coupling. Thus, it is necessary to study the inverter operation boundary and the control rule by fully considering the quantitative power coupling. In this article, a power coupling index (PCI) oriented stability analysis and [P Q]-[ω V] interactive control design for inverter-based microgrid is comprehensively studied. First, a unified inverter control framework is introduced to work under any type of network impedance. Then, a generalized PCI is constructed based on relative gain array analysis method to characterize the degree of power coupling, which facilitates interpretation of the general adaptability of the proposed control method. Meanwhile, the mechanism of power coupling and system stability under different line X/R ratio are analyzed, and interestingly, it is found that the design rules of control parameters between highly-inductive and highly-resistive line impedances are totally inverse. Finally, the comparative experiments verify the results of PCI-oriented stability analysis and the proposed universal control.