Wind Farm Structures* Impact on Harmonic Emission and Grid

Report
Wind Farm Structures’ Impact on Harmonic
Emission and Grid Interaction
Harmonics in Large
Offshore Wind Farms
Łukasz Kocewiak (DONG Energy)
Jesper Hjerrild (DONG Energy),
Claus Leth Bak (Aalborg University)
Contents
 Onshore Wind Farms
 Karnice Wind Farm
 Offshore Wind Farms
 Horns Rev 2 Offshore Wind Farm
 Models of Wind Farm Components
 Harmonic Impedance
 Karnice Wind Farm Impedance Plots
 Horns Rev 2 Impedance Plots
 Results Comparison
 Harmonic Level at Connection Point
 Conclusions
Analysed Wind Farms
 Horns Rev 2 and Karnice Wind
Farm
 Wind farms built and owned by
DONG Energy A/S
 Two different wind farms:
onshore and large offshore
 Equipped with the same
SWT-2.3-93 wind turbines
 Connected to completely different networks
 Wind turbines are equipped with full-scale converters
Onshore Wind Farm
- Karnice Wind Farm
 Onshore wind situated in the
north part of Poland
 The wind farm consists 13
SWT-2.3-93 wind turbines
 Total capacity is 30 MW
 Karnice Wind Farm is connected
directly to the distribution
network
Offshore Wind Farm
- Horns Rev 2 Offshore Wind Farm
 The biggest offshore wind
farm in the world
 Situated by the west coast
of southern Denmark
 The wind farm consists 91
SWT-2.3-93 wind turbines
 Total capacity is 210 MW
 Horns Rev 2 is connected to the network by
100 km HVAC submarine and underground cable
source: Energinet.dk
Models of Wind Farm Components
 High and Medium Voltage Cables
 Wind Turbine and Park Transformers
 Shunt Reactors
 Capacitor Banks
 External Network
Models of Wind Farm Components
- Medium and High Voltage Cables
Power Cable Impedance
 Lumped Π and T models
ZT
Magnitude |Z| [ ]
 Equivalent Π model
40
30
Z eq
20
10
 Medium voltage cables
equivalent impedance
0
calculated based on aggregated
100
model
 Frequency of interest:
50Hz – 3 kHz
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
4
x 10
50
Angle Z [ ]
 Approximation of the skin
effect using correction
factors
Z
0
-50
-100
0.5
1
1.5
2
2.5
3
Frequency f[Hz]
3.5
4
4.5
5
4
x 10
Models of Wind Farm Components
- Wind Turbine and Park Transformers
 Harmonic models based on
measurements and data
provided by manufacturers
 Models based on frequency
sweep analyzer measurements
 Measurements performed using
FRAX FSA within the confines of
internal research projects
 Frequency of interest:
50Hz – 3 kHz
Models of Wind Farm Components
- External Network
 Frequency characteristic at the point of common coupling
 Different short circuit levels, network configurations considered
 Frequency of interest: 50Hz – 3 kHz
Harmonic Impedance
- Karnice Wind Farm
Harmonic Impedance
- Horns Rev 2 Offshore Wind Farm
Results Comparison
Harmonic Level at Connection Point
 Large wind farms significantly
change impedance at PCC
 Voltage THD much lower during
wind farm production
 11th and 13th voltage harmonics
change significantly
Conclusions
 Offshore wind farms are mainly connected to the
transmission network by long HV cables
 Offshore wind farms have much more components which
have influence on overall system impedance
 Medium voltage cables network is much bigger in offshore
wind farms
 Large offshore wind farms can operate as a power plant
and improve power quality at the point of connection
 Every large wind farm has to be analysed separately
Thank You

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