Semi-direct drive model 

The concept of semi-direct drive comes into being in the process of the large-scale development of direct drive and doubly-fed wind turbines, and it has the characteristics of both. In terms of structure, semi-direct drive is similar to doubly-fed drive, which has the characteristics of various layout forms, but its appearance is similar to direct drive. There are some differences between semi-direct drive fan, doubly-fed fan and direct drive fan. First, compared with doubly-fed fan, the gearbox of semi-direct drive has a lower transmission ratio. Second, compared with the direct drive model, the semi-direct drive generator speed is high. This determines that on the one hand, semi-direct drive can improve the reliability and service life of gear box, and at the same time, compared with direct drive generator, can take into account the corresponding generator design, improve the design and manufacturing conditions of high-power direct drive generator.

 Direct drive model 

Direct drive permanent magnet wind turbine eliminates the heavy acceleration gear box, the generator shaft is directly connected to the blade shaft, the rotor speed changes with the wind speed, the frequency of its alternating current also changes with it, through the high power power electronic converter placed on the ground to rectify the variable frequency of alternating current into direct current, and then inverter into alternating current output with the same frequency as the power grid. Its main components include: impeller blade, hub, variable rotor system, generator rotor, generator stator, yaw system, wind measurement system, bottom plate, tower and so on. It has the advantages of strong grid compatibility, low maintenance cost, low noise, but difficult to transport and hoist.

 Doubly-fed machine 

The impeller of the doubly-fed wind turbine drives the generator through the multistage gear growth box. The main structure includes the wind wheel, transmission device, generator, converter system, control system, etc. The double-fed wind turbine system converts the mechanical energy transferred from the gear box to the main shaft of the generator into electrical energy, which is transmitted to the power grid through the stator and rotor of the generator.

Doubly-fed wind turbine has the advantages of mature technology, reliable quality, high efficiency, excellent cost performance, good maintainability, good power quality, strong low voltage crossing ability and so on. However, the gear box is a component with a high failure rate, and it is installed in the narrow space at the top of the tower. Once the fault occurs, it is very difficult to repair.