Certification tests for newly developed wind turbines in the field often require a considerable period of time, as tests need to be performed in certain wind conditions, which, however, are not available on demand. This makes it difficult to estimate the actual duration of a measuring campaign and, consequently, the conclusion date of the certification process. On the other hand, production needs to be initiated as soon as successful certification is completed. On the test bench, different wind conditions can be set exactly at any time, repeated as often as required, and scheduled precisely.
Field trials can be simulated under realistic conditions in the laboratory: Wind torque is reproduced using two excited synchronous motors; The reproduction of mechanical wind loads such as driving torques or bending moments are created by hydraulic force application. A 36,000 V medium-voltage grid emulator was used to test short circuits and other events in the grid with a high repetition rate, thus shortening the duration of the test. This was met with great interest by the industry, for which the launch of a pioneering new turbine concept promises a considerable competitive advantage.
Access to operating data from the research turbine offers the opportunity of comparing field data with data from the DyNaLab for validating and optimizing test methods further.
Next upgrading steps
The next development step will involve considerable expansion of the functionalities of the existing grid emulator in the DyNaLab: As a result, it will be possible to replicate both extremely weak grids and special harmonic interference spectra. This will increase the value of the existing infrastructure significantly: the institute will adopt a leading global role when it comes to innovative testing procedures for grid integration as a result. It will also open up new possibilities for testing system perturbations, oscillations, and interferences cost-effectively and comprehensively prior to commissioning of the prototype turbine in the field. Real-time models and hardware-in-the-loop (HiL) control algorithms replicate real loads and interactions between the nacelle and rotor on the test bench.
Fraunhofer IWES has been witnessing a constant demand for services in the fields of electrical certification testing and realistic development tests for existing and future generator/converter systems for wind turbines with classic two- to three-stage gears. In order to do justice to this requirement, the “HiL-GridCop” project, funded by the BMWi, and with the goal of performing automated certification of wind turbines in the laboratory, was launched in mid-2017. The setting up of a corresponding testing infrastructure and the development of a correlating testing method are also planned. In contrast to the testing of complete nacelles in the DyNaLab, this considerably smaller test bench will only be used to test minimal systems comprising a high-speed generator and converter system. The results will also discussed with certification authorities, to pave the way for acceptance of the innovative new testing methodology across the sector.