The grid-connected technology of micro turbine for dual mode operation

Dual mode running characters and grid-connected technology with two different structured micro turbines (MT) are compared and analyzed respectively in this paper. Firstly, the operating modes of MT are introduced briefly. Then operating characters and influence on traditional system protection are analyzed while MTs are connecting to the grid. The different dual mode schemes are compared via simulating different 10 kV line fault cases. Simulation results indicated that type II MT connected with grid via synchronal generator supplied larger short-circuit current, as well as worse influence on superior protection and equipment-selecting than those of type I MT which is connected with grid by converter. Further more, although type II MT can realize seamless transition, type II MT needs more strict mode transform condition than type I does, such as needing to coordinate the protection settings of turbine and system, and a braking resistance box should be used when MT is changing operating mode from grid connected (GC) mode to stand alone (SA) mode. While being grid-connected, type II MT is prone to be effected by other 10 kV lines fault. Contrarily, although type I turbine can not transform seamlessly, it has little influence on superior system protection and switchgear-selecting, as well as supplying low short circuit current.