This news article was originally written in Spanish. It has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, no automated translation is perfect nor is it intended to replace a human translator. The original article in Spanish can be viewed at Mejorar la conexión a la red y el control de los aerogeneradores

A thesis brings improvements to make wind turbines operate at very high powers and under a more stable network connection

Improve the connection to the network and control of wind turbines

Drafting Interempresas24/01/2011

on January 24, 2011

Energy wind party advantage before renewable competitors. For this reason, the presence and size of the turbines is growing and require adjustments for various reasons. On the one hand, new wind turbines need to operate at high powers, surpassing the current electronic and structural limits. On the other hand, the new regulations have been updated in accordance with the high current penetration of wind energy in the grid, and turbines require a more comprehensive control for a more stable network.

The engineer of Tecnalia Eider Robles has designed a series of solutions to enable turbines to fulfil these requirements. His thesis, defended in the BASQUE country, is entitled ' Grid connection and control of multipole synchronous wind turbines'.

Robles has opted for a mechanism of direct drive (which do not need a gearbox of speed) accompanied by a full power converter. This would be the basis for access to higher levels of power and efficiency. Such a mechanism is, in turn, very demanding with regard to the properties of the elements that must be the system, so the engineer has proposed a design in line with him.

Eider Robles, Tecnalia engineer and author of the thesis, defended his work in the BASQUE country. Photo: Eider Robles Sestafe.

Generator and converters

Regards the type of generator, the thesis identifies as the most appropriate the synchronous generator of permanent magnets (GSIP) with external rotor. The GSIP is a type of generator that does not need rings contact to transmit electricity. Thus, the rotating movement of the rotor does not cause friction, reduced losses in the copper, and decreases the need for maintenance. In addition, the fact that the rotor is external allows to attach the blades directly, which would make it possible to minimize the weight of the mechanical structure.

On the other hand, the thesis proposes an alternative to work at a higher power. At present, semiconductor devices have limitations of voltage and current, so the inclusion of all the power converters (and as has Oaks as a basis) would be impossible to wind turbines of several megawatts. Therefore, the thesis proposes to use multilevel converters, because they allow the use in series of semiconductors, and in this case it would be feasible to overcome constraints and obtain a higher voltage. For even greater quality, the researcher has proposed to add a system which offsets the external shocks such as the variations of wind. It controls 'feedforward' or of frontloading, which have the capacity to react to changes in their environment.

Positive sequence, the main contribution detectors

The requirements to be met by a system of power connected to the network, among the tasks of control to contrast the imbalances and distortions that occur in the voltage. This control is also a prerequisite to meet new regulations, which require a continuous operation of the turbines, irrespective of the imbalances, distortions and other disturbances.

For more stability and greater efficiency in the network connection, the main objective of this thesis was, precisely, the design of robust methods of detection of positive sequence. The voltage is composed of positive sequence (the useful part), but also of other components caused by imbalances and distortions. Detectors, composed by algorithmic sequences, isolate the positive sequence.

Robles has done an exhaustive review of the current detectors of positive sequence and synchronization techniques. As explained in the thesis, the main problem found in this analysis is that, in general, these detectors are specialized in one type of disturbance or another, but not all simultaneously. Finally, Robles has solved this problem with the use of four detectors of positive sequence, which is based on filters called MAF (averaging local, English Moving Average Filters filters). These detectors show a time of settlement fast and constant in the presence of any type of disruption, even if different disturbances occur at the same time.

Large turbines involve problems on which the thesis of Eider Robles has worked. (Photo: Eider Robles Sestafe).

Eider Robles Sestafe (Bilbao, 1980) is automatic and electronic engineering from the University of Deusto. He has made the thesis under the direction of José Luis Martín González (Professor of the Department of electronics and telecommunications of the school technical Superior engineering of Bilbao, UPV/EHU) and Josep Pou Felix (Professor of electronic engineering from the Polytechnic University of Catalonia). Currently, Robles is a researcher of Tecnalia, Centre which has made the thesis within the group for research on energy conversion. Both the thesis and the work of the group have been carried out in collaboration with the Universitat Politècnica de Catalunya and the school technical Superior in engineering of the UPV/EHU.