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Wind rotor inertia and variable efficiency: fundamental limits on their use for power system stabili

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Related work. New behaviours proposed, simulated, tested. Ramp rate ... Outputs of study form a physical assessment: Not an economic one. Simulation Assumptions ... – PowerPoint PPT presentation

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Title: Wind rotor inertia and variable efficiency: fundamental limits on their use for power system stabili


1
"Wind rotor inertia and variable efficiency
fundamental limits on their use for power system
stabilization"
April 3rd, Track DT1, 0900-1030 Verification
and modeling of wind power plant capabilities
  • Presented by Barry Rawn
  • PhD Candidate, Energy Systems Group, Dept of ECE,
    University of Toronto

2
Contributions to power system stability by wind
farms
  • Increased proportion of wind farms replace
    energy, power supplied by traditional generators
  • does not replace their contributions to
    stabilization
  • Effects observed in studies
  • alteration of power system mode damping
  • reduction of system inertia for primary response
  • increased governor actuation
  • Turbines have untapped technical potential
  • power electronic interface
  • Variable speed and pitch

Grid codes already require some ancillary
services constraints regarding active power
exist and will increase
3
Related work
  • New behaviours proposed, simulated, tested
  • Ramp rate limiting
  • spinning reserve
  • frequency regulation
  • Active power output control investigated (mostly
    by pitch)
  • power reference tracking by farm
  • Emulated inertial response
  • Power system stabilization

Capabilities studied in test systems. Physical
limits acknowledged but not characterized
4
Nature of Study
Outputs of study form a physical assessment
  • Chart dynamic and component limitations on
    specifying active power variations for stability
  • Available energy for primary response
  • Guaranteed amplitudes for sinusoidal variations
  • Reduction of power variations by allowing speed
    variations
  • Focus on turbine rather than test system

Not an economic one
  • Cost of providing services (e.g. due to reduced
    energy capture) not examined
  • Value of providing services not assessed
  • Focus on a single machine, not farm

5
Simulation Assumptions
  • Single full-converter turbine
  • Operation below rated windspeed
  • Pitch assumed constant, optimal
  • Pitch controls not modelled
  • Single mass model with constraints
  • Speed and converter rating limit
  • Ensemble of synthetic winds
  • Selection of mean speed

Goal to produce operating envelope indicating
dependence on mean wind
6
Experiments
  • Studied three types of active power capabilities
  • block power pulses delivering fixed quantity of
    energy
  • sustained sinusoidal variations
  • smoothing of wind power by introducing filter
  • Conducted binary search for critical magnitudes
    as limited by stability or component constraints
  • duration of power pulse
  • Amplitude of variation
  • Time constant
  • Repeated over ensemble of 100 wind series for
    each operating point and mean windspeed

7
Results relevant to PSS
  • Stability limit only for low wind, low frequency
  • Lower frequencies more limited
  • Power and speed limitations relegate operation to
    below 8 m/s

8
Results relevant to primary response
  • Available per-unit inertia predictable fraction
    of rated
  • Limited by both stability and converter rating
  • Providing constant power pulse much more
    restrictive

9
Results relevant to frequency regulation
  • Smoothing in AGC frequency band can be adjustably
    achieved
  • Comparable to inter-turbine smoothing within a
    farm

10
Conclusions
  • Contributions possible, limited largely by
    component ratings
  • Large sinusoidal variations can be delivered in
    frequency range of inter-area oscillations
  • Available energy for primary response
  • Capability can be reasonably estimated
  • Operating point dependent

11
Future work
  • Examine operational and economic implications
  • Timing of available capability and system need
  • Risk, energy capture vs compensation for service
  • Assess pitch controls
  • Study alteration
  • Extension and exploitation
  • Assess farm potential
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