The integration of wind generation to the grid is growing rapidly across the world. As a result, grid operators have introduced the so-called grid codes (GC), which nowadays include a range of technical conditions and requirements, which wind generators must fulfill. Among these, the low voltage ride through (LVRT) is a requirement for wind turbines to stay connected to the grid and continue to operate during the disturbance. In this study, a control structure, combining inertial kinetic energy storage with a crowbar circuit, is proposed to enhance the ride-through capability of a wind turbine generator (WTG) based on a wound-field synchronous generator (WFSG) under unsymmetrical voltage dips. For the grid-side converter (GSC), a decoupled double synchronous reference frame (DDSRF) d-q current controller is used. Furthermore, a Second-Order Sliding Mode Controller (SOSMC) with Super-twisting (ST) algorithm is proposed for the GSC and the machine-side converter (MSC) to improve the response speed and achieve an accurate regulation of the dq-axis current components simultaneously. The main objectives of the GSC are to achieve a balanced, sinusoidal current and smooth the real and reactive powers to reduce the influence of the negative sequence voltage. A series of simulations are presented to demonstrate the effectiveness of the proposed control scheme in improving the LVRT capability of the WFSG-driven wind turbine and the power quality of the system under unbalanced grid voltage conditions.
The paper proposes a new sliding mode power control strategy for a wound-field synchronous generator-based variable speed wind energy conversion systems to maximize the power extracted from the wind turbine. The proposed controller can handle the inherent nonlinearities in wind energy conversion systems and the randomness of the wind speed as well as the uncertainties of the model and external disturbances. To reduce the chattering phenomenon that characterizes conventional sliding mode control, a sigmoid function with a variable boundary layer is proposed. The adaptive switching gains are adjusted on-line by using a fuzzy logic-based technique. Several simulation scenarios were performed to evaluate the performance of the proposed control scheme. The results demonstrate that this controller provides excellent response characteristics, is robust against parameter variations, and free from chattering phenomenon as compared with the conventional sliding mode control.
Original scientific paperThis paper proposes a new robust fuzzy gain scheduling of RST controller for a Wind Energy Conversion System (WECS) based on a doubly fed induction generator (DFIG). First, a designed fuzzy gain scheduling of RST controller is investigated, in which fuzzy rules are utilized on-line to adapt the RST controller parameters based on the error and its first time derivative. The aim of the work is to apply and compare the dynamic performances of two types of controllers (namely, Polynomial RST and Fuzzy-RST) for the WECS. A vector control with stator flux orientation of the DFIG is also presented in order to achieve control of active and reactive power of the wind turbine transmitted to the grid and to make the wind turbine adaptable to different constraints. The results obtained by simulation prove the effectiveness of the proposed controller in terms of decoupling, robustness and dynamic performance for different operating conditions.Key words: Fuzzy gain scheduling, Wind energy conversion system (WECS), Fuzzy-RST, DFIG, Robustness Robusno neizrazito prilagoavanje pojačanja RST regulatora za WECS dvostruko napajani asinkroni generator. U radu je predloženo novo robusno prilagoavanje pojačanja RST regulatora za sustav za pretvorbu energije vjetra (WECS) s dvostruko napajanim asinkronim generatorom (DFIG). Prije svega istražena je sinteza neizrazitog prilagoavanja pojačanja RST regulatora u kojem su neizrazita pravila iskorištena on-line za adaptaciju parametara RST regulatora koji koristi signal pogreške i njegovu prvu vremensku derivaciju. Cilj rada primjena je i usporedba dinamičkih svojstava dva tipa regulatora (polinomski RST i neizraziti RST) za WECS. Takoer je prikazano vektorsko upravljanje s orijentacijom statorskog toka DFIG-a za postizanje upravljanja aktivnom i reaktivnom snagom vjetroagregata koja se predaje mreži te za prilagodbu vjetroagregata za različita ograničenja. Rezultati prikupljeni provedenim simulacijama pokazuju efektivnost predloženog regulatora kroz rasrpegnutost, robusnost i dinamičke performanse za različite uvjete rada.Ključne riječi: Neizrazito prilagoavanje pojačanja regulatora, sustav za pretvorbu energije vjetra (WECS), neizraziti RST, DFIG, robusnost
In this paper, a decoupling control strategy has been applied to control the active and reactive powers generated by a Double Feed Induction Generator (DFIG). We propose a robust nonlinear control based on Backstepping with integral actions in order to control the power of the wind turbine transmitted to the grid and to make the wind turbine adaptable to different constraints. The proposed control laws are derived from the Lyapunov approach which is well suited for this nonlinear system. Furthermore, the proposed integral backstepping control is compared with the classical backstepping controller. The results obtained by simulation prove the effectiveness of the control strategies in terms of decoupling, robustness and dynamic performance for different operating conditions Streszczenie. W artykule opisano strategię sterowania sprzęgania do kontroli mocy czynnej i biernej wytwarzanej przez generator DFIG. Wykorzystano metodę Lapunowa do kontroli turbiny wiatrowej dołączonej do sieci. Nieliniowe sterowanie backstepping do kontroli konwersji energii wiatrowej w generatorze DFIG
A new hybrid control method for controlling back-to-back converter in permanent magnet synchronous generator wind turbines Control of a hybrid wind turbine/battery energy storage power generation system considering statistical wind characteristics J. Renewable Sustainable Energy 4, 053105 (2012); 10.1063/1.4751472Control strategies of doubly fed induction generator-based wind turbine system with new rotor current protection topology J. Renewable Sustainable Energy 4, 043123 (2012);This paper presents a simulation study of the control of a variable speed wind energy conversion system (WECS) using a wound field synchronous generator (WFSG). The proposed scheme is based on an RST controller with adaptive fuzzy gain scheduling (AFGS-RST) and regulates the active and reactive powers exchanged between the stator of the WFSG and the grid to ensure a Maximum Power Point Tracking of the WECS. The overall system model was implemented in MATLAB/Simulink with three different power controllers (the polynomial RST, the fuzzy logic controller, and the AFGS-RST controller). The performances of these controllers are evaluated under different operating conditions of the WECS power system. The results demonstrate that AFGS-RST controller is very effective in improving the power flow and very robust against variable transmission line parameters compared to the two other controllers. V C 2015 AIP Publishing LLC.
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