Environmental Engineering Reference
In-Depth Information
However, the electromagnetic construction of the PMSG is more complex than
in the case of conventional WT concepts such as fixed-speed with squirrel
induction generators and variable-speed with doubly-fed induction generators, etc.
Also, the reduced gear ratio may require an increase in the number of generator
pole pairs, which complicates the generator construction [
1
-
8
].
MW class WTs have been commissioned in large (offshore) wind farms con-
nected directly to transmission networks. However, increased wind power gener-
ation has influenced the overall power system operation and planning in terms of
power quality, security, stability, and voltage control [
9
-
14
]. The local power flow
pattern and the system's dynamic characteristics change when large WTs are
connected to the utility grid [
15
]. Thus, compliance with the grid codes of national
Transmission System Operators (TSOs) becomes an important issue [
16
].
Therefore, the interaction between WFs and power systems is a research topic
that needs more attention. To get a better understanding of how the control systems
of the individual WTs and WFs influence each other, modeling and simulation are
essential. To investigate the interaction between controllers of WTs or WFs and
the controllers of the grid is considered a challenge. With more advanced control
algorithms, WTs and WFs can provide ancillary services to the grid, e.g., by
providing reactive power or participate in voltage/frequency control. To study the
impacts of these advanced control strategies on a system level, more modeling
efforts are required.
Therefore, this chapter presents the detail system modeling and the control
design of a PMSG-based-WT. Also, alternative design and/or control solutions are
proposed to improve the voltage control at a required location such as a point-
of-common coupling (PCC).
This chapter is organized as follows: The detail dynamic model including voltage
source converter (VSC) control design is presented in Sect.
1.2
; in Sect.
1.3
, the
supervisory reactive-power control scheme is proposed; case studies are carried out
in Sect.
1.4
; and conclusions are drawn in Sect.
1.5
.
1.2 Dynamic Model of PMSG-WT-Based Power Systems
The system considered in this chapter is shown in Fig.
1.1
. The WF consists of
5 units of WT. Each WT is equipped with a 0.69/22.9 kV step-up transformer
(TR). The WF is connected to the grid using a 2 km submarine cable (Ca) and a
14 km overhead transmission line (TL). The considered operating condition is as
follows: the WF supplies 7 MW of active power and 0.3 MVar of reactive power
to the local load, which consumes 8 MW and 1.9 MVar. The remaining active
power comes through the 154 kV utility grid, which is represented by an infinite
bus.
Although the fundamental principle of a WT is straightforward, modern WTs
are complex systems. The design and optimization of the WT's blades, drive train,
