DFIG fault ride through improvement during VSC faults

Abstract

The sensitivity of the doubly fed induction generator (DFIG) to external faults has motivated researchers to investigate the impact of various grid disturbances such as voltage sag and short circuit faults on the fault ride through (FRT) capability of the DFIG. However, no attention has been given to the impact of internal faults within voltage source converters (VSCs) that interface the DFIG with the grid, on the dynamic performance of the machine. This paper investigates the impact of various VSC faults on the dynamic performance and the FRT capability of the DFIG. Faults such as fire-through and flashover within the VSC switches are considered in this paper. Moreover, faults across the DC-link capacitor are included in this study as a common problem in the VSCs. The impact of these faults when they occur within the grid side converter (GSC) and rotor side converter (RSC) are investigated. A proper STATCOM controller to mitigate the effects of these faults on the FRT is proposed. The DFIG compliance with numerous and recently released FRT grid codes under these faults with and without the STATCOM are examined and compared. Furthermore, the capability of a proposed controller to bring the voltage profile at the point of common coupling (PCC) to the nominal steady-state level under five possible VSC faults cases is examined. The proposed controller is efficient, simple, and easy to implement.