IEEE Electrification - March 2022 - 60

Is There a Better Wind Turbine Topology
for Grid Stability?
So what are the specific distinctions among all three considered
turbine types in terms of their impact on the grid and
their ability to address these integration challenges in the
evolving grid? In Table 1, we consolidate some comparative
knowledge points about specific grid integration challenges.
Note that Table 1 is for the potential benefit of comparison
among three wind turbine topologies. While Type V
wind turbines represent about 10% of New Zealand's wind
power and the generator-AVR combination is well-proven
in diesel generators and elsewhere, there is much less
experience of their deployment in wind power plants
worldwide, relative to Types 3 and 4.
Based on the Table 1 comparison among different grid
integration challenges for three different GFM turbine
topologies, all of them can provide a multitude of grid services
for stabilizing the grid and for facilitating very high
shares of IBRs. The main difference between the power
electronics converter-based topologies (Types 3 and 4) and
the synchronous topology (Type 5) is whether most of the
services can be provided via controls or by natural
TABLE 1. A comparison of advantages for specific turbine types.
Grid Integration Challenge
Weak grid operation
Type 3
Yes, with controls
Type 4
Type 5
Yes, no controls needed, tends to
make grid stronger
Operation at sites with low short-circuit
ratio (SCR) yet to be demonstrated
Short circuit current contribution
Contribution to system inertia
Limited
Inertia-like
response using
controls, no
curtailment
Fast frequency response
Primary frequency response
Independent control of active and
reactive power
Transient performance and ridethrough
Voltage
control
GFM operation
No, unless significantly
oversized
Inertia-like response using
controls, with curtailment
High, no controls needed
Yes, no controls or curtailment needed
(for example, a two-pole generator would
give four-times real inertia compared to
a four-pole generator)
Yes, fast response with special controls, curtailment, and/or transient uprating
Yes, fast response with special controls and curtailment
Participation in frequency regulation Yes, curtailment needed
Yes, with controls
Yes, with special controls
Yes, with special controls
Yes, with controls
Black start and islanded operation Yes, with controls and energy storage
Medium-voltage operation
Protection impacts
Yes, with step-up transformer; transformerless
might be possible in the future
May require adjustment to protection to
accommodate lower short-circuit current
than synchronous generation
(Type 3 has more SCC capability than Type 4)
Wind-free voltage support
Yes, with special controls (voltage control only,
no inertia)
Brushless operation
Generator
Cybersecurity
Brushes needed Yes
Special design
Yes
Yes, curtailment needed
Yes, with controllable automatic voltage
regulator (AVR)
Yes, same as conventional synchronous
generator with AVR
Yes, same as conventional synchronous
generator with AVR
Yes, no controls (default operation mode)
Yes, no controls
Yes, up to 20 kV with no transformer
No change in the existing protection
framework
Yes, with clutch to disconnect generator
from gearbox (synchronous condenser
mode, provides voltage control and
inertia, enhances grid strength)
Yes
Special design, dependence on
rare-earth minerals for permanent
magnet generators
Yes
Mass produced, global maintenance
network and workforce exists, no dependence
on rare-earth minerals
Fewer controls means fewer targets for
external attacks
60
IEEE Electrification Magazine / MARCH 2022
IEEE Electrification - March 2022

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