Adaptive-Observer-Based Control of a Real-World Grid-Forming Converter-Interfaced Shaft Generator in a Shipboard Microgrid

This article proposes a new strategy for integrating a new type of distributed generation (DG) into a shipboard microgrid (MG). The study focuses on the application of a shaft generator (SG) system, which is the first inverter-based DG installed in most large-sized ships. The squirrel-cage induction generator commonly used for the SG system is examined for control stability, and an adaptive observer is proposed to estimate the stator resistance of the SG. The proposed strategy includes integrating virtual impedance control into the inner control loop of the grid-forming converter for smooth integration of the inverter-based DG in the shipboard MG, and adopting a self-secondary voltage controller to regulate voltage deviation and share reactive power in the MG. An eigenvalue analysis is conducted to evaluate the proposed strategy, and simulation and experimental studies are carried out to verify that they accurately estimate the stator resistance of the SG, provide sufficient inertia to the DG for stability, and improve voltage regulation in the shipboard MG.