Wind turbine power capability is an essential set ofdata for both wind turbine manufacturers/operators and transmissionsystem operators since the power capability determineswhether a wind turbine is able to fulfill transmission system reactivepower requirements and how much it is able to providereactive power support as an ancillary service. For multimegawattfull-scale wind turbines, power capability depends on convertertopology and semiconductor switch technology. As power capabilitylimiting factors, switch current, semiconductor junction temperature,and converter output voltage are addressed in this studyfor the three-level neutral-point-clamped voltage source converter(3L-NPC-VSC) and 3L Active NPC VSC (3L-ANPC-VSC) withpress-pack insulated gate bipolar transistors employed as a gridsideconverter. In order to investigate these VSCs’ power capabilitiesunder various operating conditions with respect to theselimiting factors, a power capability generation algorithm based onthe converter electrothermal model is developed. Built consideringthe VSCs’ operation principles and physical structure, the model isvalidated by a 2MV·A single-phase 3L-ANPC-VSC test setup. Thepower capability investigations regarding a sample grid code’s reactivepower requirement showthat 3L-ANPC-VSC results in 32%better power capability than 3L-NPC-VSC at the switching frequencyof 1050 Hz. Furthermore, 3L-ANPC-VSC with 57% higherswitching frequency (1650 Hz) and 33% smaller switching ripplefilter can yield close power capability compared to 3L-NPC-VSCwith 1050 Hz.