Ana Susperregui

DFIG Power Generation Capability and Feasibility Regions Under Unbalanced Grid Voltage Conditions

Several strategies have been proposed for operating doubly-fed induction generator (DFIG)-based wind turbine under unbalanced grid voltage conditions. This study focuses on those strategies in which the rotor-side power converter aims at eliminating the oscillations affecting the electromagnetic torque and the stator reactive power. Given the limited size of the DFIGs power converters, and hence their tolerable current and voltage boundaries, this study analyzes which DFIG power generation capability is under unbalanced grid voltage, and therefrom derives rotor current and stator power controllable ranges. Besides, the feasibility regions of the DFIG are also deduced for different types of imbalance. Furthermore, and based on the outcome of previous analysis, a modified rotor current limiter, as also its equivalent stator power limiter, is proposed. In contrast to the conventional ones, the limiters proposed here take into account that imbalances may arise in the grid voltage. As a consequence, systems overall performance is considerably enhanced under unbalanced grid voltage conditions. Finally, simulation results establish the validity of the treated issues.

Methodology for Smooth Connection of Doubly Fed Induction Generators to the Grid

A systematic methodology for smooth connection of wind-turbine-driven doubly fed induction generators (DFIGs) to the grid is presented. Synchronization of the voltage induced in the DFIG open stator to that of the grid, which needs to be accomplished prior to connection, is thoroughly examined. A particular grid-voltage-oriented rotor control scheme is considered for this purpose. Generic tuning equations for the rotor current integral-proportional (I-P) controllers involved in this scheme are also derived. Transition between the control configurations devoted to synchronization and normal operation-active power generation and reactive power interchange with the grid-at the instant of connection is studied in detail. Mainly due to the reference frame selected for synchronization, the greater part of this transition takes place naturally. However, given that the rotor current dynamics vary significantly depending on whether the DFIG stator is connected to the grid or not, the parameters of the I-P controllers involved in both schemes will accordingly be different. Consequently, a ldquobumplessrdquo strategy is provided that preserves the smoothness of the connection. A simple method for initial rotor positioning, required when performing vector control based on an incremental encoder, is also suggested. The resulting overall methodology is validated on a 7-kW DFIG-based laboratory-scale test bench.

Interface evaluation for cultural heritage applications: the case of FERRUM exhibition

Intuitive access to information in real environments is a challenge for Information Society Technologies. Having this in mind, a new device for Mixed Reality applications called Virtual Showcase has been developed. It has been conceived to be used in museums and exhibitions, due to its compatibility with traditional museum showcases, offering additional information to the public by means of a simple, direct and intuitive interface. This paper presents the real implementation and usability evaluation of a Virtual Showcase passive-stereo prototype exhibited in a museum for three months. Some results concerning the evaluation process have also been included. Although the technology seems to be promising, implementation aspects such as size should be improved.

Sliding-Mode Control for a DFIG-Based Wind Turbine under Unbalanced Voltage

Abstract This paper reports a first-order sliding-mode control (1-SMC) design for controlling the doubly-fed induction generator (DFIG)-based wind turbines rotor-side power converter. The design is particularly focused on keeping the generator successfully in operation under unbalanced grid voltage conditions, as todays grid codes require. Aside from controlling the stator-side active and reactive powers’ average value, the rotor-side converter is commanded so as to remove the fluctuations affecting the electromagnetic torque and the reactive power during unbalanced voltage. The paper aims to put forward the bases of the proposed design together with the described algorithms stability proof. Finally, the appropriateness of the sliding-mode control to deal with the aforementioned disturbed scenarios is supported by means of simulation results.

Providing On-Site Augmented Information to Tourists

Knowledge about the world is increasingly visually articulated. Moreover, the importance of vision in human understanding of the world as well as the visual nature of tourism has been widely recognised by tourism ‘professionals’ and academics. Depiction, picturing and seeing are ubiquitous features of the processes by which most tourist learn about the world. Visual technologies are increasingly becoming part of many individuals’ everyday experience. If tourist organizations liked to reach wider audiences, they would have to build attractive multimedia content that attracts tourists. Therefore, new systems that support these innovative applications and provide added-value content are required.

Student-tailored final year project on microcontroller-based hardware-in-the-loop speed control of a wind generator

Student-supervisor cooperation was carried out to design the inter-subject final year project reported in this paper. According to the student feedback, this approach allowed gathering his main interests – vector control, microcontroller programming and wind power generation – together, therefore reinforcing his motivation towards his final year project and making him feel particularly responsible for its outcome. Microcontroller-based hardware-in-the-loop emulation made possible to combine the three afore-cited student interests. In this context, the virtual prototype of a current-controlled wind turbine-driven 2-MW permanent-magnet synchronous generator is presented, along with the pseudo-code corresponding to the permanent-magnet synchronous generator speed control algorithm programmed in an 8-bit microcontroller. In addition, tuning formulas are derived for the digital integral-proportional controllers commanding both the permanent-magnet synchronous generator current and speed. Detailed descriptions are provided in order to guarantee reproducibility. Implementation of the hardware-in-the-loop rig is also tackled, supported by illustrative results obtained when running it. The developed hardware-in-the-loop rig is considered suitable for laboratory practices of subjects like digital control and microcontroller programming.

Application of Virtual Showcase technologies in real scenarios: the case of San Telmo museum

Intuitive access to information in real environments is a challenge for information society technologies. Having this in mind, a new device for mixed reality applications called Virtual Showcase has been developed. It has been conceived to be used in museums and exhibitions, due to its compatibility with traditional museum showcases, offering additional information to the public by means of a simple, direct and intuitive interface. We present the real implementation of a Virtual Showcase passive-stereo prototype exhibited in a museum for three months. Some preliminary results concerning the evaluation process have also been included. Although the technology seems to be promising, implementation aspects such as size should be improved