Study on Variable Speed Wind Turbines

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Study on Variable Speed Wind Turbines
Capabilities for Frequency Response
Germán Claudio Tarnowski - Technical University
of Denmark Vestas Wind Systems A/S Jacob
Østergaard - Technical University of
Denmark Poul E. Sørensen - Risø National
Laboratory, Denmark Philip C. Kjær - Vestas Wind
Systems A/S, Denmark
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Outline

• Introduction variable speed wind turbine
  frequency response for grid frequency stability.
• Simulation set-up
• Small/low inertia power system with wind power
• Models
• Simulation cases generation trip
• Conventional generation only (Base Case)
• Wind power Without inertia response
• Wind power Inertia response
• Wind power Inertia response Primary frequency
  control
• Conclusions remarks

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Introduction

• Grid frequency variations ? Imbalance between
  generation and consumption
• Wind Turbine Frequency Response
• Change in the wind turbine active power output
  as response to a change in the grid frequency
• Inertia response (power from rotating kinetic
  energy)
• Primary frequency control (power from wind
  reserve)
• Study on capabilities of WT-DFIG for providing
  controlled frequency response during frequency
  drop in a small/low inertia power system,
  combining inertia response and primary frequency
  control

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Simulation set-up WT-DFIG model

• Drive train
• 3rd order DFIG
• Converter control active and reactive power.

• Aerodynamics

• Pitch control rotational speed

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Wind turbine frequency response

• Inertia response (inertia emulation)
• Primary frequency control (Droop)
• Plant power reserve (reserve factor)

WT control block
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Simulation set-up Power system
Conventional generators
Capacity Inertia Type
ST1 100 MVA H 3.5 Reheat steam turbine
ST2 150 MVA H 6 Reheat steam turbine
HT 50 MVA H 5 Hydro turbine
Tripped 50 MW - -
Load 250 MW - active
50 MW Generation Loss (20)
Wind Farm replacing ST1 30 Wind Power Penetration
  Capacity Type
WF 100 MVA Wind Farm
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Simulation set-up Conventional generatorsmodel
Model for Steam Power Plant and Hydro Power Plant
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Simulation cases Inertia response from wind
turbine

1. Grid with conventional generators
2. Grid without inertia response from WT
3. Grid with inertia response from WT

Gen. Unit R FR ?PR MW Heq (s)
Base case ST1 6 0.3 30 5
Base case ST2 5 0.3 30 5
Base case HT 5 0.33 50 5
Case 2 WF Without inertia response Without inertia response Without inertia response 3.8
Case 3 WF Inertia response Inertia response Inertia response 5
50 MW Generation Loss (20)
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Results Grid frequency
Grid Frequency Hz

1. Conventional generators case
2. WT without inertia response case
3. WT with inertia response case

Frequency gradient
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Results Power plants electric power output
Power MW
Steam turbine ST2

1. Conventional generators
2. Wind power without inertia response
3. Inertia response from wind power

Steam turbine ST1
Wind turbine
Hydro turbine
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WT inertia response
Powers pu
Torques pu
Rotational speed pu
Pitch angle deg
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Simulation cases inertia response primary
frequency control

1. Droop 16 Inertia response
2. Droop 10 Inertia response
3. Droop 9 Inertia response (Instability)

Gen. Unit R FR ?PR MW Heq (s)
Case 4 WF 16 0.1 8 5
Case 5 WF 10 0.15 12 5
Case 6 WF 9 0.15 12 5
50 MW Generation Loss (20)
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Results Grid frequency
Grid Frequency Hz

• Conventional generators
• WT Droop 16 Inertia response
• WT Droop 10 Inertia response

Frequency gradient
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Results Power plants electric power output
Power MW
Steam turbine ST2

1. Conventional generators
2. Droop 16 Inertia response
3. Droop 10 Inertia response

Steam turbine ST1
Wind turbine
Hydro turbine
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Turbine droop 10 inertia response
Powers pu
Torques pu
Rotational speed pu
Pitch angle deg
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Turbine droop 9 inertia response. Instability.
Powers pu
Torques pu
Rotational speed pu
Grid Frequency Hz
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Conclusions remarks

• Variable speed WTs capabilities for inertia
  response and primary frequency control was
  studied
• Suitable control systems for variable speed WTs
  need to be developed for integrating high amounts
  of wind power in the grid
• Grid frequency stability can be improved
  combining WT inertia response and primary
  frequency control
• Instability in wind turbines with bad settings of
  primary control and inertia response Capability
  depends on the combination of droop value, power
  reserve and inertia emulation.

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Thank you for your attentionGermán C.
TARNOWSKIgct_at_elektro.dtu.dk