ABB ACS800-67, System Description And Start-Up Manual

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System description 13
2
System description
What this chapter contains
This chapter describes the main components of a wind turbine and describes the
functionality of the wind turbine converter as a part of a complete wind turbine system.
General
Variable-speed wind turbine concepts can be divided in two main categories, wind turbine
systems equipped with a doubly-fed asynchronous generator or wind turbine systems
equipped with an induction generator like squirrel-cage-, synchronous- or permanent
magnet synchronous generator. Difference between these concepts is that in doubly-fed
systems one-third of the rated generator power is fed through the wind turbine converter to
the 3-phase electrical power network (grid) while in systems equipped with eg, permanent
magnet synchronous generators whole power is fed through the wind turbine converter to
the electrical power network.
In wind power applications, the doubly-fed asynchronous generator rotor is accelerated by
the wind and the mechanical speed is controlled by the pitch of the blades to stay within
the operating speed range until the wind turbine converter is started. In order to stop the
wind turbine converter, the breaker(s) is/are opened and the rotor is braked to standstill by
pitch control and mechanical brakes. Doubly-fed systems have typically a gear box for
coupling the generator shaft to turbine hub, active control of turbine blade pitch for
maximizing production and controlling mechanical speed, and variable speed operation
depending on the rating of the wind turbine converter relative to turbine rating (eg, ±30% of
the generator synchronous speed).