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2.0 System Description
NOTICE: Use of the material contained in this document is subject to the warning on page Iv and the disclaimer
on page v of this document.
DOC012R02 AOC 15/50 User Manual Nov 2001
11
2.2 Control System Description
The following parameters are monitored by the wind turbine’s control system. It initiates
shutdowns when faults have been detected to protect the wind turbine from mechanical and
electrical damage.
UTILITY NETWORK:
• Over/under voltage
• Phase loss
• Phase reversal
• Over/under frequency (optional)
TURBINE:
• Generator temperature
• Rotor speed
• Power (derived from rotor speed)
• Parking brake current
SYSTEM:
• Wind speed (redundant anemometers)
• Ambient temperature switch (optional)
2.3 Operation Description
The AOC 15/50 is a downwind turbine, i.e. its blades rotate downwind of the drive train
assembly. Furthermore, it has no active yaw control and depends on its blades to track the wind.
In winds outside of the required wind band, the PLC (Programmable Logic Controller)
disconnects the wind turbine from the grid and parks it; the wind turbine is brought to a complete
stop. The parking brake remains applied, thereby preventing the blades from rotating. However,
they will still track the wind and the wind turbine will pivot about its yaw bearing accordingly.
The AOC 15/50 has three main modes of operation: test, off and on. The setting of the
TEST/OFF/ON switch determines the parameters monitored by the PLC and which other
switches can be activated. When the turbine TEST/OFF/ON switch is set to OFF, the PLC only
monitors grid faults.
Once the turbine TEST/OFF/ON switch is set to ON, the PLC starts evaluating the wind speed
data which, together with the generator rotor speed, is the most important source of input data to
the PLC; grid related parameters and thermal relays play a secondary role.
The wind speed is measured using two cup anemometers. For the wind turbine operation the
wind speed has to fall within the specified speed band of 3.6-22.3 m/s (8-50 mph). The cut-in
speed of 4.9 m/s (11 mph) is slightly higher than its minimum operational speed because of the