Recent Advances in Variable Speed Electrical Generator Systems for Large Wind Turbines

摘要

Major variable speed electrical generator system design objectives have been verified through large-scale experiment. Full exploitation of variable speed generator benefits can revolutionize large wind turbine design. The greatest advantages come not only from the improved aerodynamic efficiency of keeping tip speed proportional to wind speed, but from dramatic reduction in drive train resonances, elimination of dissipative damping losses, easy motorized turbine start, and isolation of turbine dynamics from the electrical network. Experimental verification proceeded by two steps: first, actual control hardware and software were verified with a hybrid simulation of a full wind turbine system; then the controls were combined with power thyristor bridges configured as a cycloconverter and motor-generator test train to implement a variable speed generator and a simulated wind-turbine/drive train. Although the existing equipment presented several constraints on testing latitude, major features demonstrated include: (1) variable frequency motoring to 50% speed for quick, efficient turbine start-up; (2) synchronization below, at, and above synchronous speeds, both steady state and transient; (3) net power output up to 120 kW with stable response to 50 kW step changes in demand within one second and similarly responsive control of VARs; (4) steady power and VAR output throughout speed transients from ten percent below to ten percent above synchronous speed; (5) output voltage waveform with less than five percent total harmonic distortion; and (6) damping of simulated drive train resonance at 0.2 Hz. (ERA citation 09:000460)