We’ve taken another step forward with our power conversion system controls. Superior grid performance has now been confirmed by our professional team using our sophisticated testing process at The Switch high power laboratory in Vaasa.
Over the years, we’ve learned about the importance of the power quality produced for a grid by wind turbines and other similar electrical energy-producing applications. The basics were known. Yet from conducting studies, laboratory tests and certification tests in the field with entire turbine systems, we have become the experts in providing superior performance with our converters.
Our customers and wind park owners have recognized our technology and solutions that provide good grid connectivity for individual wind turbines as well as for entire wind parks.
Now there’s more good news: The next generation FPC+ series is now demonstrating first-rate grid performance and an enhanced fault ride-through (FRT) strategy.
The FPC+ series, using The Switch’s latest hardware and system software solutions, enables more responsive functionality and a higher margin in operating voltage to manage abnormal conditions. This complies with the grid code to ensure that the feeding capacity of the reactive components supports a failing grid, even during high-voltage grid conditions.
Limits of recognized grid codes vs. performance of The Switch FPC+ series.
Example of the power feeding (PQ) capacity of The Switch’s FPC+ series.
Another important compliance criterion is related to the power quality the converter produces under normal operation, in other words, the grid harmonics.
To mitigate low-frequency grid harmonics, one solution is to apply a filter between the converter and the grid. All conventional technology filters, including LC, LCR, or LCL, are available with the FPC+ portfolio to match different grid requirements.
A standard solution would be an LC filter that provides adequate harmonic performance with grid transformer impedance at a proper ratio to the converter capacity. In our opinion, this solution is currently the best way forward to maximize energy production and minimize costs.
Today’s conventional solutions, however, still use rather bulky, magnetic components and capacitors to form the filter, which take up real estate in the converter. Therefore, research is now focusing on finding a more sophisticated technique, such as an active harmonics injection, to lower the harmonics and reduce the size and cost of both the filter and converter.
For this to work, a wider bandwidth in feedback circuits and carrier frequencies within the drive modules would be needed to provide adequate grid control and compensate for the harmonics. And although this technique could be implemented, it would increase inverter losses, costs and end up lowering the capacity to feed active power to the grid.
Moreover, it is hard to justify why the equipment dedicated to electrical power conversion and electrical energy production should compensate for grid harmonics, especially since the converter itself does not directly produce them.
Moving towards the future, The Switch is taking it as our mission to continuously seek improvements to these passive filter solutions and continue to enhance the world of power conversion systems.
Alpo Vallinmäki
Director of Converter Technology