Environmental Engineering Reference
In-Depth Information
Chapter 5
Wind Energy Systems
5.1 General
In some applications the rotor operates within power and speed limits on its natural
characteristic, e.g. with a centrifugal pump as load. Power limitation in rotors with
rigid blade angle may be effected by passive acting measures such as spoilers or
braking flaps. For machines of small rating also passive pitching mechanisms, e.g.
by means of pre-loaded springs, are known. Speed limiting methods acting on the
load side such as feeding energy into a dump resistor are also restricted to small
ratings.
Systems for electrical power generation of other than small ratings will generally
require active control measures. While pitching allows speed control on the wind
side, suitable generator systems provide control possibilities on the electrical side.
Operation management has the task to provide an efficient, failure-free and safe
operation. It controls switching on and off of generator and other electrical systems,
auxiliary systems such as hydraulic pitching equipment and braking procedures.
The task implies state monitoring and surveillance of the protective devices. This
requires continuous measuring of weather data, operational and grid data, and pro-
cessing in the operation management computer.
5.2 Systems Overview
5.2.1 General
In conversion systems to supply electrical energy the wind rotor is coupled, gener-
ally via a gear box, with an electrical generator in form of an induction machine or
a synchronous machine. In variable speed systems power electronic equipment is
used to decouple voltages and frequencies of generation and grid side.
Wind energy systems may be operated according to the following concepts:
constant speed (as for mains fed synchronous machines), or almost constant
speed (as for the shunt characteristic of mains fed induction machines),
variable speed (as for generators with frequency decoupling by inverters).
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