Environmental Engineering Reference
In-Depth Information
Figure 8 : Swing rudder (Courtesy of Zephyr Corporation).
Figure 9 : Yaw control system with downwind WT (Courtesy of Proven Energy Ltd.).
7.2 Passive yaw control with downwind system
With downwind WTs, the rotor functions as a tail wing and it has passive yawing-
function to make WTs follow the wind direction. A typical commercial downwind
wind turbine is shown in Figure 9. No power source is necessary for yaw control,
but stability of yaw motion needs to be carefully investigated, because when one
more freedom of the system is added, instability could happen under accelerated
or decelerated conditions of rotor speeds.
8 Power/speed control
Power control/rotor speed control is an essential part of whole system, upon which
both performance and safety depend. As described in the previous sessions, an
optimal aerodynamic performance design can start, provided a feasible power/
speed control is available.
8.1 Initial start-up control
A WT with pitch control system are capable to make start-up at lower wind speed by
regulating the pitch angle of the blades. However, SWTs of fi xed pitch rotor blades
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