As more and more wind turbines are connected to the national grid, the need for better systems to ensure grid stability increases commensurably. The so-called “fault-ride-through capability” (FRT) of a wind turbine – in other words, not to disconnect from the grid during sudden voltage dips and surges in the power grid – and the provision of reactive power for compensating for frequency fluctuations are just some of the requirements that new wind turbines must fulfil.
But the process of validating wind turbines for service until now has been complicated and long-drawn-out. Therefore the Fraunhofer Institute for Wind Energy Systems (IWES) in Bremerhaven, northern Germany, joined forces with the turbine manufacturer Nordex Group three years ago to develop a hardware-in-the-loop (HiL) test rig at IWES to verify all the components of a turbine and electronic converters in real time, including the testing of the electrical drive train on a grid simulator – all independently of the weather.
Michael Franke, VP global engineering at the Nordex Group, explains the significance of the new HiL facility in a : “Field validation of turbine system characteristics is necessary but time-consuming,” he says. “Added to this is the difficulty of finding a suitable test site for the series of tests. Measuring the grid-related properties of a turbine in the field takes more than 12 months until certification. The same test on the IWES test stand could now be completed in three months – a time saving of nine months. With the test rig, both partners have succeeded in taking a big step, because it enables faster market access.”