Scientists at the Carlos III University of Madrid (UC3M) have designed a new control system for wind turbines in offshore wind farms, that allows a simpler, more flexible and cheaper electrical connection to the coast compared to current solutions.
This innovation, protected by a set of patents from these UC3M researchers, could be easily implemented in offshore wind farms that are far from the coast since, in order to transmit the energy they produce, they must transform the alternating current (with which these wind turbines operate), in direct current (which is used in the direct current high voltage transmission systems, -HVDC High Voltage Direct Current-, that carry the electricity to the land power stations).
The researchers have developed a distributed control system that enables the synchronization and regulation of voltage and electrical frequency of the entire group of wind turbines
To achieve this, the researchers have developed a distributed control system that enables the synchronization and regulation of voltage and electrical frequency of the entire group of wind turbines. This makes it possible to feed energy into the general network through an HVDC link with a diode rectifier station. “It is less complex, cheaper and more flexible than other current solutions”, explained one of the authors of the patents, Santiago Arnaltes Gómez, responsible for the Power Control group at UC3M.
This new system synchronizes the wind turbines without using any element or additional line, since it uses the capacity of the wind turbines to contribute to the voltage-frequency control. One of the keys to achieve this lies in the use of diode rectifier stations, which allow reducing the cost of facilities up to 30%, according to some studies. “What we have achieved is to provide the technical feasibility necessary for the use of this type of rectifiers, since up to now the wind turbines were not able to operate with them,” explains another of the authors of the patent, José Luis Rodríguez Amenedo, from the Department of Electrical Engineering of UC3M.
Flexible and economical connection of offshore wind farms with the coast
Arnaltes explais how from the UC3M “we have developed a family of patents that enable the offshore wind farms connection to a direct current link for the transmission of energy to the power system.” When offshore wind farms are connected to a direct current power link it becomes necessary to generate voltage and frequency for those parks, “that is what the current stations that are VSC type do”.
“Our main customers would be large utilities with the capacity to build these diode rectifier stations”
Specifically, the researchers have developed three patents related to this system, which have been validated through simulations, small-scale laboratory prototypes and concept tests. The next step is their marketing and industrialization. For Rodríguez Amenedo, the main advantage lies in that these systems use diode rectifier stations that are “much cheaper and make it possible to reduce the cost and, therefore, make the system economically viable”, which is why “our main customers would be large utilities with the capacity to build these diode rectifier stations.” The UC3M Science Park has backed researchers for the management and marketing of this new technological solution.
Currently, the integration of offshore wind farms in the continental electricity systems is being considered throughout the world as an alternative for reducing fossil fuel consumption and greenhouse gas emissions. Because a large part of the large projected offshore wind farms are located far from the coast, the connection with HVDC links (in direct current) is technically and economically more appropriate than an HVAC transmission system (in alternating current).