Design of high-efficiency converters for large direct-drive wind turbines

The stator voltage of generator is usually 690 V for large MW direct-drive wind turbine so that the current rating is very high. As a result, the full-size converters are difficult to be designed and manufactured, moreover, the efficiency problem is considerable. This paper proposed a solution based on the multiphase permanent magnet synchronous generator (MPPMSG) with hybrid three-level full-size converters, which is thought as an alternative for the traditional three-phase PMSG with the shunted two-level converters and expected to offer better harmonic properties and efficiency. The paper discussed the parameter design of the different converters used in the proposed system. And the harmonics, efficiency and costs were compared with the traditional two-level system.