Performance and Operation Management - Wind Energy Systems for Electric Power Generation - page 133

Fig. 6.11 Analogy of PV- and wind energy systems

Increase speed set-point if Decrease speed set point if

Δ P > 0 and ΔΩ ≥ 0 Δ P < 0 and ΔΩ ≥ 0

or Δ P < 0 and ΔΩ < 0 or Δ P > 0 and ΔΩ < 0

command signal is used in the following active power control loop of a
field-oriented control. Note that measuring the wind speed is not necessary.
Other publications describe variants of the method under the name of Hill-Climb
Searching (HCS), e.g. [Wan04] who use an on-line training process and intelligent
memory.

The Ω

6.3.1.3 Multiple Input Control

Larger systems which normally feed into public grids receive their command values
from the operation management. Controlled variables are normally active power P
and speed n ; in systems containing inverters also reactive power Q . Internal con-
trolled variables can be, depending on system features, the pitch angle

β and stator

and rotor voltages and currents.
The control concepts are usually closed-loop schemes, containing one or more
loops in cascade arrangement. Controllers are mostly of the PI-type. Functional di-
agrams are frequently used to describe the structure and calculate input and output
quantities.

6.3.2 Control of Systems Feeding into the Grid

6.3.2.1 Functional Diagrams

Regarding systems for grid supply, the following block diagrams illustrate the basic
control concepts.