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
2Contributions 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
3Related 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
4Nature 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
5Simulation 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
6Experiments
- 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
7Results 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
8Results 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
9Results relevant to frequency regulation
- Smoothing in AGC frequency band can be adjustably
achieved - Comparable to inter-turbine smoothing within a
farm
10Conclusions
- 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
11Future 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