Previous research has shown that a variable speed electrical system with a brushless synchronous generator and a DC-link is a promising option for large and more advanced flexible wind turbines. It has also been shown that vibrations in the mechanical transmission, which are often observed in variable speed wind turbines, can be reduced by the use of a well designed controller. Prior to applying this new controller, the model used for the controller design has to be verified and the controller has to be tested in practice. Therefore a test-rig of the system has been designed and realized, using a DC-motor to simulate the wind turbine. A flywheel and a flexible shaft are part of the test-rig to obtain the same oscillatory behaviour as in the actual wind turbine. The controller is implemented on a process computer in a shell programme which performs all control and safeguard actions necessary in wind turbines. A description is given of the test-rig and the integral controller. Implementation of grid faults and firing failure of the thyristors will also be discussed. 4 figs., 4 refs.