Voltage collapse phenomena in wind parks

Wind power is rapidly growing in the world. For reasons of economy the network interconnection is often designed without redundancy. This means that the nominal power of the transformer to the transmission system is in the range of the nominal power of all wind generators of a wind farm. Short circuit faults are in power systems unavoidable and cause a temporary instability of power transfer. In systems with weak network interconnection the problem of fast voltage collapse is prominent. Today double fed asynchronous generators play a major role in the upper power class of wind generators with variable rotor speed. In the eastern Austrian area about 800 to 1.200 MW of wind power will be installed within only 4 years. In this area wind farms of up to 50 MW have to be interconnected. As the interconnection to the existing 380 kV network in this area is weak, voltage fluctuations and voltage stability can be a problem in the future. For the planning of the network interconnection and the analysis of voltage collapse problems a simulation model has been established. For double fed asynchronous generators an advanced simulation model, based on park´s equations together with inertia mass of rotor, gear and generator is used. The rectifier and inverter of the rotor feeding control circuits are included in the model and have been compared in their transient behavior with measurements. With help of this advanced model of double fed asynchronous generators, the behavior of wind farms under realistic network conditions has been investigated. To medium voltage network configurations are compared: ring feeding and radial feeding system.