The doubly fed induction generators (DFIGs) are used in almost 50% of the offshore and onshore wind power plants. The DFIGs offer advantages compared to fix speed induction generators. The DFIGs are sensitive to grid voltage disturbances and require additional protection for the rotor side power electronic converter, like crowbar protection. In the present paper two active crowbar topologies are compared, IGBT with bypass resistor and rectifier with IGBT, which were the most studied in the scientific literature. A DFIG model with analyzed crowbar protections was implemented in Matlab/Simulink. The simulation results reveal that both solutions can limit the rotor current and the dc link voltage values. However, the solution with rectifier offers better results
For digital native generations, augmented reality (AR) represents a friendly way to enrich reality with virtual, computer‐generated elements. Considering the students’ proficiency for the use of smartphones, internet and of continuously refreshing applications, AR is very suited for a modern engineering education. In this field, AR supports a better understanding and a thorough learning, while increasing the commitment and the motivation for learning. The paper presents the step‐by‐step approach to the AR technology adopted within the Power Engineering Faculty of the University POLITEHNICA of Bucharest, Romania. Such an approach lets students and teachers time to get used to the change, to adjust the vision of AR implementation according to the results obtained so far and to keep up to the newest available technologies. Based on the Aurasma free platform, augmented information, images, and videos were created to appear in books, presentations, and on experimental units for three laboratories. Within the paper, the way in which AR works, may be directly experienced by the reader, as it was by a group of students and faculty members included in a pilot study. According to their feedback, the use of AR in power engineering education facilitates a better understanding of this complex technical domain, providing new and challenging opportunities to integrate theory with practice and to acquire authentic skills in their professional areas.
The paper analyzes the capability of a wind power plant, based on doubly-fed induction generators (DFIGs) with an improved control system, to fulfill low voltage ride-through (LVRT) capability of the wind turbines providing the reactive power support. According to grid code requirements, tripping of wind generators under grid faults is not allowed. The sensitivity of DFIGs to grid faults requires the use of crowbar protection for not damaging the electronic equipment. In this paper, the model of a wind power plant based on DFIG using active crowbar protection is developed in Matlab/Simulink. Nevertheless, the results indicate that DFIGs equipped with crowbar protection can protect the electronic equipment, but the rotor side converter is blocked due to crowbar activation and the reactive power control is lost. Therefore, for improving the LVRT, a coordinated control system of the grid side converter, active crowbar protection, and rotor side converter is implemented and proposed, The grid side converter of DFIG is controlled similar to a STATCOM, considering also the control parameters of the crowbar protection. The simulation results show that the proposed coordinated control grid side converter'active crowbar-rotor side converter can supply the reactive power in order to answer the grid codes requirement for LVRT. Therefore, this control system can be useful to improve the LVRT capability of wind power plants based on DFIG
This paper proposes a control system, for crowbar protection and voltage support, for wind turbines equipped with doubly fed induction generator. The control system based on PI controller enables the low voltage ride through capability of the wind turbines. The reactive power control of doubly fed induction generators is mostly achieved by controlling its rotor side converter. The proposed control system allows regulating the reactive power using the rotor side converter as well as the grid side converter. During crowbar activation, the rotor side converter can no more control the reactive power. The proposed system controls the voltage at the point of common coupling to be above the imposed low voltage ride through curve, until the grid side converter returns to normal operation. The proposed models were implemented in Matlab/Simulink. The case studies refer to a control system with hysteresis band for the crowbar protection of a 3MW doubly fed induction generator based wind turbine. The simulation results highlights that the proposed control improves the coordination between grid side converter, rotor side converter, and crowbar protection
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