Combined low voltage ride through and power smoothing control for DFIG/PMSG hybrid wind energy conversion system employing a SMES-based AC-DC unified power quality conditioner

摘要

An Interline AC-DC unified power quality conditioner (UPQC) protection device is proposed and designed based on superconducting magnetic energy storage (SMES) in this paper to improve low voltage ride through (LVRT) capacity and smooth output power for doubly fed induction generator (DFIG)/ permanent magnet synchronous generator (PMSG) hybrid wind energy conversion system (WECS). The AC side of the proposed UPQC is connected in series with the terminal of DFIG as a dynamic voltage restorer (DVR), and the DC side of the UPQC is connected in parallel with the DC bus of PMSG for DC bus voltage maintenance and output power adjustment. For a case verification, a 4.76-H/1760-A superconducting coil (SC) is designed as an energy storage device utilized in UPQC to carry out the energy conversion. Finally, the performances of the proposed protection scheme under the conditions of wind speed variation, three-phase-to-ground fault and two-phase-to-ground fault have been presented and analyzed via simulation, to verify the effectiveness of the proposed AC-DC UPQC in DFIG/ PMSG hybrid WECS.