High temperature superconducting (HTS) generators could enable a lightweight and cost-effective direct drive (DD) wind turbines with large power ratings. The EU-funded EcoSwing project successfully demonstrated the world's first full-scale MW-class HTS generator on a commercial DD wind turbine. This paper focuses on the commissioning of the EcoSwing HTS generator on the wind turbine. The commissioning campaigns, including the rotor cool-down, excitation of the HTS field winding, and the power production of the generator, are presented in the paper. In the testing period, the generator was grid-connected for more than 650 hours and accumulatively produced more than 600 MWh to the grid. The target output power of the 3 MW class was reached. Throughout the real-life testing on the wind turbine, the generator performed well from the electromagnetic, thermal, and mechanical perspectives. Moreover, the generator even sustained three sudden short circuits in the converter system. The work reported has shown that HTS generators are technologically feasible for wind turbine applications, and the technology readiness level of HTS wind turbine generators has been improved to 6 similar to 7 for the first time.