Abstract
Pertaining to the connectivity issues in wind power plants with grids, this study introduces an efficient mechanism based on a state feedback control structure to establish a fast and stable grid connection for a wind-driven doubly-fed induction generator (DFIG). Owing to a direct link through stator windings, a DFIG is significantly vulnerable to grid disturbances and experiences sizable inrush currents when connected to the power grid. The proposed control structure is designed based on a linear matrix inequality stabilization criterion, which is framed using a suitable Lyapunov candidate function. The control objective is to ensure that the stator voltage can exponentially converge to the grid voltage, accounting for balanced and unbalanced grid conditions. This is achieved by generating appropriate rotor voltage references for rotor-side converter control. This study also explores the capability of the proposed control structure to enhance the system’s robustness to external disturbances and uncertain parametric variations. Simulations confirmed the effectiveness and suitability of the developed structure in mitigating the adverse effects of the rapid onset of the grid voltage at the stator terminals of the DFIG under various grid conditions; the proposed structure could thus establish a reliable connection with negligible effects on the DFIG and the grid.
Highlights
The advantages of soft and fast grid synchronization are twofold: (1) It permits the grid connection of a doubly-fed induction generator (DFIG) with the least impact on the power system, and (2) it enables the fast reclosing of DFIGs immediately after grid faults, which is favorable in terms of providing voltage support to the grid and improving the fault ride-through capability of wind-energy conversion systems (WECSs)
DFIGs are widely adopted solutions for variable-speed WECSs and constitute a significant fraction of the energy generated by wind power owing to reduced-rating power electronic converters [10], unlike its counterpart, which is connected to the grid through full-scale converters [11]
This study focused on an important issue pertaining to the integration of wind power plants (WPPs), i.e., the smooth and soft grid connection of a DFIG-based WECS
Summary
An increase in the share of wind energy in existing electric networks affects the dynamic behaviors of power systems. Grid synchronization is significant for aligning highly stable system operations with wind-driven doubly-fed induction generators (DFIGs). It involves the voltage amplitude, phase angle, and frequency between the wind-turbine-generator terminal voltage and the grid voltage, with minimal deviations before establishing a connection [7,8,9]. DFIGs are widely adopted solutions for variable-speed WECSs and constitute a significant fraction of the energy generated by wind power owing to reduced-rating power electronic converters [10], unlike its counterpart, which is connected to the grid through full-scale converters [11]. Despite playing a vital role in WECSs, a DFIG is susceptible to power-system transients owing to a direct grid connection through its stator windings. The rotor circuit and wind power converters (WPCs) experience these transients and further complicate the control of the DFIG
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