Grid Connection of a Converter Controlled Squirrel-Cage Induction Generator

The paper presents a grid connection process of a converter controlled squirrel-cage induction generator driven by an uncontrolled speed prime mover. The main goal of the described method is to decrease an inrush current during a grid connection of an induction generator. The converter is used for a build-up process of a generator voltage and afterwards for a synchronization of the generator voltage with the grid voltage. The synchronization process is made by loading the induction generator with the brake-choppers, connected to the DC-link of the NPC converter. When the squirrel-cage induction generator is connected to the grid, the power electronic converter works as a reactive current source to satisfy the reactive power demand of the generator. The tests have been performed in the laboratory setup with a 7.5 kW induction generator and 8.0 kVA power transformer.