Facility Employing Standard Converters for Testing DFIG Wind Generators up to 30kW

This paper presents a test facility for a double fed induction generator (DFIG) with a rated power of approximately 30 kW. The stator of the machine is directly connected to the grid and the rotor is fed with variable voltage and frequency. Actually such machines are used in wind generators with a power of more than 500 kW with special built converters. In the presented test facility the used converter consists of two standard low cost voltage source converter units with connected DC-link. The firmware of these converters are normally not suitable for feeding the rotor because there are not able to calculate the slip frequency and phase in real time. In the presented solution this is programmed in two application modules plugged into the converter. The equivalent network parameters of the DFIG are determined by the converter. These are necessary for the development of an analytical model of the system to set up a closed loop active and reactive power control. The test system provides the ability to control both power types decoupled and with a linear characteristic