Novel Autonomous Control of Grid-Forming DGs to Realize 100% Renewable Energy Grids

초록

The grid-forming distributed generators (GFM-DGs) have attracted much attention as a key technology for realizing 100% renewable energy grids. This paper presents a novel control strategy to ensure the reliable operation of a renewable energy source (RES)-based GFM-DG during weather variations. The GFM-DG connects a RES to the grid via source-and grid-side converters, with their common DC-link voltage VDC indicating the power balance between the RES and the grid. We begin by identifying the limitation of conventional strategies in maintaining VDC during severe weather. To address the limitation, we propose a coordinated strategy for both source-and grid-side converters to regulate VDC cooperatively, ensuring GFM-DG stability even in adverse weather conditions while also achieving decentralized power sharing and contributions to frequency inertia and damping. The proposed strategy is applicable to photovoltaic-and wind turbine-based generators, as well as energy storage systems. A guideline for control parameter design and stability margin analysis for weather conditions are also provided. The effectiveness of the proposed strategy is validated via small-signal analysis and simulation case studies under various conditions of 100% renewable energy grids, characterized by severe weather, load demand changes, actual line impedances, and a grid fault.

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