Permanent Magnet Synchronous Generator (PMSG) in Wind Power Plant

Permanent Magnet Synchronous Generator (PMSG) in Wind Power Plant

• This is also a variable speed generator.

• This type of synchronous generator is shown in the following block diagram of wind power plant.

Main components of Permanent Magnet Synchronous Generator :

1. Blade and turbine rotor assembly.
2. Permanent magnet synchronous generator.
3. Power converting unit rectifier and inverter.
4. 3-phase step-up transformer from which 3-phase A.C. power is fed to grid.
5. Blade turbine assembly (1) Is rotated by wind power. The rotation of steam turbine rotor gives mechanical power to generator (2) for converting into electrical power.

Permanent Magnet Synchronous Generator :

Stator :

• Is stator is similar as stator of previous WRSG type. 3-phase y connected stator winding in which 3-phase voltage is induced is directly fed to grid system. The output voltage prior to connect to grid is stepped up by 3-phase transformer (5). 

Rotor :

• Rotor structure is provided with permanent magnets pole system.

Power Converter Unit (3) and (4) :

• This unit provides operation of power plant to operate at different speeds/ frequencies. 
• The rectifier unit converts variable frequency/ variable amplitude A.C. voltage of generator into d.c. voltage at variable level.
• It is a charge controller.
• Inverter converts this D.C. Into A.C. at grid frequency level, voltage level and phase angle.
• Active and reactive power flow is controlled by the same power converter unit.

Working in short of Permanent Magnet Synchronous Generator :

• Wind power rotates rotor of wind turbine, it rotates rotor of permanent magnet type synchronous generator. The field of rotor rotates with rotor and stator stationary coils cut the flux of rotor magnet and emf Is Induced in stator coils.
• Rectifier/ Inverter unit converts variable voltage and variable frequency output into constant frequency (50-60 Hz) and constant magnitude voltage. This stable voltage from stator goes to grid circuit to connect the power from this wind power station to grid system.

Advantages and Disadvantages of Permanent Magnet Synchronous Generator :

Advantages of Permanent Magnet Synchronous Generator :

1. Construction is simple.
2. It is robust.
3. Cheaper In cost.
4. No excitation system is required (as permanent magnets).
5. High frequency.
6. Low loss.
7. No gear box is needed.
8. Power converters regulate voltage and active and reactive power flow.
9. Power factor is controlled.

Disadvantages of Permanent Magnet Synchronous Generator :

1. Difficulty of non-availability of large size permanent magnets, so useful for small/ medium size wind power plants only.
2. Possibility of de-magnetisation permanent magnet.
3. Complicated structural dynamics.
4. Need cooling system to maintain temperatures within limits.