Comparative Study and Optimal Design of Subsynchronous Damping Controller in Doubly Fed Induction Generator

Abstract

The subsynchronous damping controller (SSDC) has been widely recognized for its excellent performance and low cost in subsynchronous oscillation (SSO) mitigation for the doubly fed induction generator (DFIG)-based wind power system. However, the existing SSDCs are various and lack a systematic comparison. To fill this gap, the structures and parameter design methods of common SSDCs are sorted and compared in this paper. It is found that the rotor-current-based method performs best in terms of dynamic performance and robustness, as it can mitigate SSO for all working conditions in the test, while the feasibility range of other methods is much smaller. Therefore, the influence of different parameters in a rotor-current-based SSDC on SSO mitigation is further researched, leading to a guideline for parameter selection. More importantly, to address the challenge of time-varying oscillation frequency, an adaptive frequency selection method is proposed based on the eigensystem realization algorithm, which can accurately track the SSO frequency within 5~45 Hz. The results of the root locus analysis and hardware-in-the-loop experiment demonstrate that the improved rotor-current-based SSDC performs better than other existing methods, and it does not affect the normal operation of the DFIG.

Mechanism Analysis of Multiple Disturbance Factors and Study of Suppression Strategies of DFIG Grid-Side Converters Caused by Sub-Synchronous Oscillation

“…Since 2011, several SSO accidents with oscillation frequencies of 3-10 Hz have occurred at wind farms in Guyuan, Hebei Province [10][11][12]. In 2014, an SSO accident occurred in Hami, Xinjiang, which caused the torsional vibration protection of the thermal power unit to cut off 300 km away [13][14][15][16], seriously affecting the safe operation of the power grid and the grid-connected control of the wind turbine.…”