Abstract
Wind energy conversion systems (WECSs), based on permanent magnet synchronous generators (PMSGs), are becoming common sources in dc grids. However, in previous dc grids integration studies, turbine-generator mechanical dynamics are represented by a single-mass model. A practical direct-drive connection in a PMSG-WECS yields lightly-damped torsional speed oscillations because of the double-mass mechanical nature of the generator and the wind turbine. Active damping strategies are usually employed to suppress the mechanical oscillations in a full back-to-back converter interfacing PMSG-WECSs into ac grids; nevertheless, the active damper performance in dc grids is unknown, particularly under dc grid uncertainties and, more importantly, the presence of dynamic and constant power loads commonly used in dc grids. To fill out this gap, this paper presents a detailed modeling and comprehensive stability assessment of a dc grid with a high penetration level of wind power generation. Moreover, stability enhancement strategies are proposed to increase the damping of the entire system, considering different operating and installation scenarios that might face a system integrator/designer. Time-domain simulation studies, based on nonlinear models, are conducted to validate the analytical results. Furthermore, hardware-in-loop real-time simulation studies demonstrate the feasibility of hardware implementation.
Highlights
DC grids have gained widespread acceptance in modern distribution systems because of their simple control and economical operation [1], [2]
SYSTEM RESPONSE WITHOUT PROPOSED STABILITY ENHANCEMENT METHODS The dynamic performance of the dc grid under investigation is assessed with only the permanent magnet synchronous generators (PMSGs) active damper
This paper presents a detailed modeling, comprehensive stability analysis, and stability enhancement methods for a dc grid with a high penetration level of wind power generation
Summary
DC grids (e.g., dc microgrids and dc distribution systems) have gained widespread acceptance in modern distribution systems because of their simple control and economical operation [1], [2]. Wind power generators can be directly interfaced to a dc grid via a voltage-source converter (VSC) to supply energy to dc loads or the main ac grid with the back-to-back. The effectiveness of these stabilization methods to mitigate the instabilities caused by the wind generator mechanical dynamics in dc grids has not been yet investigated. Based on the above discussion, it is obvious that comprehensive studies on the detailed modeling and stability assessment of the interaction dynamics of a wind turbine generator in dc systems are lacking in the current literature. Developing detailed small-signal models and stability assessment method of the interaction dynamics of a typical dc grid, considering the double-mass mechanical dynamics of the wind turbine generator and typical load dynamics of dc grids (e.g., constant power loads and dynamic loads).
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