Optimising electric transmission from offshore wind farms

Scientists from Universidad Carlos III de Madrid (UC3M) have designed a new control system for wind turbines in offshore wind farms which allows electric transmission to the coast in a simpler and more flexible way than current solutions.

The electric transmission innovation allows the use of a diode rectifier station in the offshore platform of a high voltage direct current (HVDC) link. This way the wind turbines’ alternating current can be easily converted into direct current for the HVDC transmission.

According to the university, researchers have developed a distributed control system which will regulate the electric voltage and frequency of the wind turbine of the offshore wind farm, allowing the transmission of energy to the network through a HVDC link with a diode rectifier station.

Santiago Arnaltes Gómez, head of the UC3M Power Control Group, said: “It is less complicated, cheaper and more flexible than other current solutions.”

The new system synchronises the wind turbines without using any additional element, as it uses the wind turbines’ capacity to contribute to voltage and frequency control.

José Luis Rodríguez Amenedo, from UC3M’s Department of Electrical Engineering, said: “What we have managed to do is to provide the technical feasibility necessary in order to use this kind of rectifiers, since at the moment wind turbines still cannot work with them.”

The integration of offshore wind farms into mainland electrical systems is currently being put forward as a way of reducing fossil fuel consumption and greenhouse gas emissions. Since a significant proportion of the large offshore wind farms planned are located far from the coast, a connection using HVDC links is technically and economically more suitable than a HVAC transmission system (in alternating current).

One of the key factors is the use of diode rectifier stations, which allow for a reduction of the cost of the offshore rectifier platform by up to 30%, according to some studies.