Wind turbines key to stable green power

A new generation of wind turbines is now emerging with the capability of flattening out voltage fluctuations in electricity networks, and thereby providing a more consistent source of renewable energy.

As a result of research at Delft University, in the Netherlands, it was discovered that the electronics equipment used to convert the electricity produced by a turbine could be reprogrammed to correct peaks and dips in the mains voltage. Researchers believe this goes a long way to overcoming the problems of fluctuating energy supply from wind power, and has potential applications across all forms of renewable energy.

The latest wind turbines are equipped with a power electronics converter that ensures that they produce the same voltage at all times, regardless of the rotor speed. This electronic system makes use of the properties of alternating current, where the voltage crosses zero a hundred times a second. By sending electricity into the network at that moment, the power electronics can boost the voltage. This does not need to cost much energy.

Working on the principle of ‘reactive power compensation’, it even works when there is no wind and the blades are not rotating. In that case, the power electronics can extract the necessary energy from the network, precisely between two zero-axis crossings. PhD student, Han Slootweg, at Delft University, told edie that the converter must have sufficient capacity – around 20%, to be modified, and that manufacturers are already beginning to supply modified models. Older windfarms cannot however be retrofitted with the new controls.

Slootweg pointed out that in the Netherlands, where windfarms currently supply regional grid companies with middle and lower voltage grids, wind generators must ensure that they do not create voltage fluctuations. Fluctuating wind supply is a challenge to these requirements but with the new modifications, future wind generators can now tackle the problem at the grid.

At the moment, the task of maintaining the stability of the mains voltage is left entirely to power stations. In future, as sustainable energy will become more important, researchers believe wind turbines and other sustainable energy sources will then need to help stabilise the mains voltage.

Slootweg is currently modelling the effect of integrating large numbers of the modified wind turbines in electrical grids. Work is also planned to adapt his model to solar power applications, he said.

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