Wind Farm Structures’ Impact on Harmonic Emission and Grid Interaction

Harmonics in LargeOffshore Wind Farms

Łukasz Kocewiak (DONG Energy)Jesper Hjerrild (DONG Energy),Claus Leth Bak (Aalborg University)

Onshore Wind Farms Karnice Wind Farm

Offshore Wind Farms Horns Rev 2 Offshore Wind Farm

Models of Wind Farm ComponentsHarmonic Impedance

Karnice Wind Farm Impedance Plots Horns Rev 2 Impedance Plots Results Comparison

Harmonic Level at Connection PointConclusions

Contents

Analysed Wind Farms

Horns Rev 2 and Karnice Wind FarmWind farms built and owned by

DONG Energy A/STwo different wind farms:

onshore and large offshoreEquipped with the same

SWT-2.3-93 wind turbines

Connected to completely different networksWind 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 13SWT-2.3-93 wind turbines

Total capacity is 30 MWKarnice Wind Farm is connected

directly to the distributionnetwork

The biggest offshore windfarm in the world

Situated by the west coastof southern Denmark

The wind farm consists 91SWT-2.3-93 wind turbines

Total capacity is 210 MWHorns Rev 2 is connected to the network by

100 km HVAC submarine and underground cable

Offshore Wind Farm- Horns Rev 2 Offshore Wind Farm

source: Energinet.dk

High and Medium Voltage CablesWind Turbine and Park TransformersShunt ReactorsCapacitor BanksExternal Network

Models of Wind Farm Components

Models of Wind Farm Components- Medium and High Voltage Cables

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 104

0

10

20

30

40

Mag

nitu

de |Z

| [

]

Power Cable Impedance

ZT

Z

Z eq

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 104

-100

-50

0

50

100A

ngle

Z

[]

Frequency f[Hz]

Lumped Π and T modelsEquivalent Π modelMedium voltage cables

equivalent impedance calculated based on aggregated model

Approximation of the skineffect using correctionfactors

Frequency of interest:50Hz – 3 kHz

Models of Wind Farm Components- Wind Turbine and Park Transformers

Harmonic models based on measurements and dataprovided by manufacturers

Models based on frequencysweep 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 couplingDifferent short circuit levels, network configurations consideredFrequency 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