Environmental Engineering Reference
In-Depth Information
14.1 Introduction
Wind turbines are complex systems with large flexible structures that work under
very turbulent and unpredictable environmental conditions and for a variable
electrical grid. When wind turbines are combined into large wind farms, additional
turbine interaction problems, grid integration issues, and cooperative control
matters add more complexity to the engineering design and control.
The efficiency and reliability of a wind farm strongly depend on the applied
control strategies. Large nonlinear characteristics and high model uncertainty due
to the interaction of the aerodynamics, mechanical, and electrical subsystems, both
at the turbine level and the wind farm level are central difficulties in the design
process. Stability problems, maximization of wind energy conversion issues, load
reduction strategies, mechanical fatigue minimization problems, reliability mat-
ters, availability aspects, and costs per kWh reduction strategies demand advanced
cooperative control systems to regulate variables such as pitch, torque, power,
rotor speed, yaw orientation, temperatures, currents, voltages, and power factors of
every wind turbine [
1
,
2
].
Every new design and control idea in the wind energy field has to be tested and
validated in a realistic scenario before moving forward to a final certification and
commercial implementation. Frequently, this experimentation and validation is
extremely expensive or even not possible. For all these reasons, this chapter
presents a new low-cost and flexible test-bench wind farm for advanced research
and education in optimum wind turbine/wind farm design and cooperative control.
14.2 System Description
Figure
14.1
shows a general view of the wind farm test-bench. It includes four
variable-speed pitch-controlled wind turbines (1), a supervisory control and data
acquisition (SCADA) system with a central control unit (2), a smart grid with
batteries for energy storage, variable electrical loads, solar panels and switches for
different grid topologies (3), and a group of fans to create different wind profiles
and disturbances (4).
14.2.1 Wind Turbine Description
Figure
14.2
shows a general view of each wind turbine unit. It is a variable-speed
pitch-controlled wind turbine composed of a multi-blade aerodynamic rotor (1)
able to support a set of 2, 3, 4, 5 or 6 blades.
The drive-train has a mechanical gearbox with a brushless induction electrical
generator (2) and a connection (11) to the grid system through the current/torque
