IEEE Transactions on Sustainable Energy, 2017
ABSTRACT: This paper proposes a novel double-fed induction generator (DFIG)-based wind-energy conversion system (WECS), which incorporates a dynamic voltage restorer (DVR) and energy storage system (ESS). The DVR is in series with the output terminal of a wind turbine generator (WTG) and parallel to the dc link of the WTG with the ESS. The control scheme of the WECS is designed to suppress wind power fluctuations and compensate grid voltage disturbances, which in turn improve the fault ride through (FRT) capability and the wind power penetration level. Finally, the performance of this WECS is investigated under various operation scenarios such as symmetrical and asymmetrical grid faults.
- Double-fed induction generator (DFIG)
- Energy storage system (ESS)
- Wind power fluctuations
- Dynamic Voltage Restorer (DVR)
- Fault Ride Through (FRT).
Fig. 1. Structure of the novel DVR-ESS-embedded WECS
EXPECTED EXPERIMENTAL RESULTS:
Fig. 2. Symmetrical grid fault with 50% voltage dip. (a) Grid voltage. (b) Compensation voltage. (c) WTG’s terminal voltage. (d) RSC/GSC current RMS. (e) Power response. (f) Additional power response. (g) State of charge. (h) DC link voltage.
Fig. 3. Symmetrical grid fault with 90% voltage dip. (a) Grid voltage. (b) Compensation voltage. (c) WTG’s terminal voltage. (d) RSC/GSC current RMS. (e) Power response. (f) Additional power response. (g) State of charge. (h) DC link voltage.
Fig. 4. System performance under asymmetrical grid fault. (a) Grid voltage. (b) Compensation voltage. (c) WTG’s terminal voltage. (d) RSC/GSC current RMS. (e) Power response. (f) Additional power response. (g) State of charge. (h) DC link voltage.
Fig. 5. Different sequence components in d-q reference frame. (a) Positive-sequence components in d-axis. (b) Positive-sequence components in q-axis. (c) Negative-sequence components in d-axis. (d) Negative-sequence components in q-axis
Fig.6 Crowbar scheme
Fig.7 WECS scheme
In this paper, a novel DVR ESS-embedded WECS is proposed. The system configuration and its control scheme are designed, and simulations are conducted under normal operation and fault operation conditions to test the system performance. The main conclusions are as follows. The embedded ESS can store surplus wind power for release when needed. By designing different power output commands, i.e., constant output power or filtered output power, the ESS can effectively suppress the wind power fluctuations and further improve the penetration level of wind power. The use of a DVR can significantly improve the FRT capability of the WECS under symmetrical and asymmetrical voltage fault conditions, and is particularly suitable for already installed DFIG-WTGs that do not possess sufficient FRT capability. During a disturbance, the blocked wind power generation is stored for subsequent use to suppress wind power fluctuations without any loss of energy.
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