Industrial application of variable speed drive system for high speed in megawatt power range

An industrial application of a high speed high power variable speed drive system with a rated power of 2300 kW at 15600 RPM is presented. The drive is based upon economical and reliable components such as thyristor controlled current source inverters and the rugged and maintenance free squirrel cage induction machine. Many synergies with the standard load commutated drive technique with synchronous machines could be made use of. The installation of a capacitive filter in parallel to the induction machine enables load commutation of the machine side converter and in addition yields sinusoidal machine voltages and currents in a limited upper speed range. Thus optimal overall efficiency of converter and induction machine is obtained. The induction machine works as a generator in order to produce electrical energy out of a gas expander station. Since the drive group is accelerated from standstill through the expander turbine no diverter is used to commutate the machine side converter during startup. The running generator is magnetized through the capacitive filter by means of self excitation. A fully digital rotor flux oriented control was implemented which did prove to be insensitive to parameter uncertainties. The operation is documented through measurements on the installed drive