Analysis on Applicability Problems of the Aggregation-Based Representation of Wind Farms Considering DFIGs' LVRT Behaviors

• Published in: IEEE transactions on power systems Vol. 31; no. 6; pp. 4953 - 4965
• Main Authors: Ruan, Jia-Yang, Lu, Zong-Xiang, Qiao, Ying, Min, Yong
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Agglomeration; Aggregation; collection network; Dynamics; Error analysis; low voltage ride-through (LVRT); Mathematical analysis; Mathematical models; nonuniformity; Power system dynamics; Power system stability; Representations; Rotors; Stators; Transient analysis; Transient stability; wind distribution; Wind farms; Wind power
• ISSN: 0885-8950; 1558-0679
• DOI: 10.1109/TPWRS.2016.2539251

Applicability problems of the widely-used aggregation-based representation of DFIG wind farms focus on the modelling "error and impact" in transient stability computation. In order to identify crucial LVRT behaviors of DFIGs, specifically in system-level analysis, control strategies including vector-orientation, closed-loop rotor-current regulation, and Crowbar protection are given a full consideration. It is proved that, the DFIG works with its electrical and mechanical dynamics decoupled, and the result is that the DFIG behaves as an ideal controlled-power source. The DFIG's power-modulation functions defined by the grid code distinguish it from the conventional synchronous generator, which also conveniently offers dominant dynamics for studying errors of aggregation. Next, errors caused by the coupling between distribution factors and LVRT behaviors of wind farms (but ignored in aggregation) are discussed. With some existing grid codes, these factors not only generate a distributive profile of residual voltages along the feeders, but more importantly nonuniform power responses among individual wind turbines. Impacts of aggregation's errors on transient stability of power systems are analyzed. The trend in the error and impact of aggregation is analytically surveyed in a rudimentary system, and further numerically verified in a multi-machine system.