Standard Wind Turbine-Generator Models

Transcription

1 Western Electricity Coordinating Council Standard Wind Turbine-Generator Models Wind Generator Modeling Group Western Electricity Coordinating Council IEEE PES 2006 Montreal, Quebec

2 It is time for a change Wind generation capacity no longer invisible 60 GW worldwide, 40 GW in Europe, >9 GW in the US, >4 GW in the WECC footprint Some regions experiencing high saturation levels Significant expansion expected in the near future Adequate simulation models are indispensable Evaluate impact of adding new generators Perform planning studies to maintain system reliability at the local and regional level The Status Quo is not acceptable One-of-a-kind, proprietary models unnecessarily difficult to refine, validate, and maintain

3 Yet another A different modeling effort WECC Wind Generator Modeling Group (MVWG) Convened by Modeling & Validation Work Group (MVWG) in 2005 WGMG Members: Abraham Ellis PNM, WECC (chair) Graeme Bathurst TNEI Services John Dunlop AWEA Yuriy Kazachkov Siemens PTI (PSS/E) John Kehler AESO, WECC Eduard Muljadi NREL William Price GE Energy (PSLF) Craig Quist PacifiCorp, WECC Joseph Seabrook Puget Sound, WECC Paul Smith ESB Grid Robert Wilson WAPA, WECC Robert Zavadill EnerNex, UWIG

4 Mission statement Invest best efforts to accomplish the following: Develop a small set of generic (non-vendor specific), non-proprietary, positive-sequence power flow and dynamic models suitable for representation of all commercial, utility-scale WTG technologies in large scale simulations The models should be suitable for typical transmission planning and system impact studies Develop a set of best practices to represent wind plants using generic models as basic building blocks Coordinate directly with wind manufacturers and other stakeholder groups outside WECC

5 Proposed standard models Four basic topologies based on grid interface Type conventional induction generator Type 2 wound rotor induction generator with variable rotor resistance Type 3 doubly-fed induction generator Type 4 full converter interface Type Type 2 Type 3 Type 4 generator Plant Feeders PF control capacitors generator Slip power as heat loss ac to dc Plant Feeders PF control capacitors generator ac to dc dc to ac Plant Feeders generator ac to dc dc to ac full power Plant Feeders partial power

6 Technical issues Complexity vs. completeness Need the right tool for the job! Wind plant equivalencing (e.g., single-generator or several-generator reduced equivalent) necessary and sufficient for both power flow and dynamic simulations Grid vs. wind disturbances Standard models are intended for studying the effects of grid disturbances, not wind disturbances For a typical wind plant, constant wind power during transient events (0 to 20-second time frame) is not a bad assumption Other tools that account for geographical diversity should be used to study the effect of wind variability in operations planning Model vs. reality Validation is required--will be challenging!

7 Wind plant equivalencing Individual WTGs and turbine-level reactive compensation (if any) POI Power Grid Station transformer & plant-level reactive compensation (if any) Collector system with several overhead and underground feeders underground)

8 Wind plant equivalencing Single-generator equivalent Planning studies typically assume rated MW output Reactive consumption/capability at the POI can be estimated, but should be field-verified Equivalent feeder impedance can be derived from design data Main station Xfm Equivalent feeder impedance and shunt admittance Equivalent generator with appropriate VAR range, depending on Pgen (*) System P.O.I. Equivalent pad-mounted transformer Equivalent low-voltage shunt compensation, if any Explicit plant-level shunt compensation, if any NOTE: In some cases, it may be desirable to define a several-generator equivalent model

9 Testing existing models Purpose Compare performance of a large number of existing custom models for specific disturbance conditions Determine whether category models would sufficiently capture dynamic behavior of commercial turbines Test System Infinite Bus 230 kv Line R, X, B 34.4/230 kv station transformer Rt, Xt kv collector system equivalent Re, Xe, Be 0.6/34.4kV equivalent GSU transformer Rte, Xte Ideal Gen 230 kv Line 2 R2, X2, B2 2 3 Station-level shunt compensation 4 Turbine-level shunt compensation 5 Gen 00 MW equivalent wind turbine generator

10 Test scenarios Scenario System SCR (pre/post fault) Fault location Clearing time (cycles) Output levels a 0 / 5 at node % output, rated wind sp. b 0 / 5 at node % of rated output (50 MW) c 0 / 5 at node % output, 25% wind sp / 0 at node % output, rated wind sp. 3 0 / 5 at node % output, rated wind sp / 0 at node % output, rated wind sp. 5 0 / 5 mid line 9 00% output, rated wind sp / 0 mid line 9 00% output, rated wind sp. 7 0 / 5 mid line 5 00% output, rated wind sp / 0 mid line 5 00% output, rated wind sp.

11 Models tested Type Make/Model MPS MWT000A Bonus.3/2.3 MW Vestas V82/72 2 Vestas V80/47 2 Suzlon 2.0 MW * 3 GE.5 Type Make/Model 3 Gamesa G80/90 3 Vestas V90 4 Enercon E70 4 Clipper 2.5 MW 4 Bonus 2.3 MW Mark II 4 GE 2.x Series ** (*) PSSE only (**) PSLF Only

12 Some lessons learned For the same WTG, model response is very similar in different platforms, even though implementation and level of detail differ Supports case for a standard model for each generic type of wind turbine generator Some existing models need improvement Technical analysis continues Manufacturers willing to cooperate Some required confidentiality arrangements

13 Type 3 standard model* Power Order Converter Control Model Speed Order Pitch Control Model I p (P) Command E q (Q) Command P gen, Q gen Shaft Speed Blade Pitch V reg bus Generator/ Converter Model Wind Turbine Model V term P gen P gen, Q gen Structure and level of user input similar to standard generator models No special EPCL / IPLAN routines Initialize directly from power flow Separate protection model * Work in progress!

14 Type 3 standard model* E q cmd From Converter Control I Pcmd V term T- V Y V X K pll ω o 0.02s 0.02s K ipll s P llmin P llmax E q I P P llmax P llmin - X eq ω o s I Yinj I Xinj δ T V term /θ I sorc jx eq Generator / Converter Model V/Q control of gen. internal Eq P control of converter Ip Phase-locked loop not instantaneous Notes:. V term and I sorc are complex values on network reference frame. 2. In steady-state, V Y = 0, V X = V term, and δ = θ. * Work in progress!

15 Type 3 standard model* V reg Wind Plant Reactive Power Control Emulation V rfq K iv / s /F st n r K pv st v Q max Q min Q wv st c Reactive Power Control Model Q, PFA, or V control Optional fast Vt control PFA ref P gen Power Factor Regulator tan - x st p Q ord 0 Q ref Q varflg gen Q max K qi / s V max V ref Q cmd Q min V min V term V term XI Qm ax K qv / s V term XI Qmin vltflg 0 E q cmd To Generator / Converter Model P gen ω (shaft speed) f ( P gen ) T sp s ω ref Σ ω err Anti-windup on Power Limits K ptrq K itrq / s X P max & dp max /dt st pc P min & -dp max /dt P ord.. I pmax I p cmd To Generator / Converter Model Active Power (Torque) Control Model To Pitch Control Model To Pitch Control Model V term * Work in progress!

16 Type 3 standard model* From Turbine M odel ω Σ ω err Anti-windup on Pitch Limits K pp K ip / s Pitch Control Σ PI max rate limit (PI rate ) θ cmd st p PI min Blade Pitch To Turbine M odel θ Pitch Control Model From Converter Control M odel ω reff P ord Σ Anti-windup on Pitch Limits K pc K ic / s Pitch Compensation Constant Wind Speed Simplified Aerodynamic Model Blade Pitch ΔP = K aero ( θ - θ o ) θ P mech = P o - ΔP From Pitch Control Model P mech From Generator M odel Σ P gen : T acc 2H D s ω To Pitch Control M odel and Converter Control M odel Wind Turbine Model * Work in progress!

17 Turbine Aerodynamic Model Detailed aerodynamics in most WTG models The mechanical power (Pmech) applied to the generator is a function of the Power Coefficient (Cp) Pmech = ½ (air density) (swept area) Cp (Vw) 3 Cp is a function of blade pitch and tip-speed ratio During a large electrical disturbance, blade pitch and tip speed ratio vary, thus Cp and Pmech will also vary Cp is modeled using a look-up table or Cp matrix specific to each WTG (usually considered confidential, proprietary information)

18 Aerodynamic Model Simplification Assume that during grid disturbances: Wind speed change is negligible Shaft speed change has negligible effect on Cp Aerodynamic model: Pm = f (θ) For variable speed WTGs (Type 3 and Type 4), investigation of detailed model has shown: Change of mechanical power (Pm) varies nearly linearly with change in pitch angle (θ) in the range 0<θ<30 deg Pm varies linearly with respect to wind speed (Vw) from cut-in to rated wind speed θ varies linearly with respect to Vw for wind speeds above rated

19 Example GE.5 (Type 3)

20 Example GE.5 (Type 3) Simplified aerodynamic model: Pm = Pm θ ( θ - θ ) / 00 Initialization: Pm = Pelec (from power flow) If Pm < Prated, θ = 0 If Pm = Prated and Vw > rated wind speed, use Fig. 9 to compute θ

21 Simplified model Case a Simplified model Case b 00% output, rated Vw 50% output Blue = standard model; Red = simplified model

22 Simplified model Case c Super-simplified Case c 00% output, 25% rated Vw Assumes constant Pm (not good!) Blue = standard model; Red = simplified model

23 Lessons learned For Type 3 and 4 WTGs, aerodynamic simplification is possible without significant loss of accuracy No need for Cp curves, etc. Model does not perform as well if aerodynamics are ignored (e.g. constant mechanical power) Similar results expected for Type and 2 WTGs Relationship between ΔPm and Δθ may not be as linear. Simplified model may involve more complicated equations.

24 Status Type 3 and 4 standard model currently under development; Types and 2 to follow Prototyping and testing models in MatLab prior to implementation is PSLF and PSSE Significant validation effort needed High-order models Field recordings (turbine and plant-level) Future Model revisions based on the same fundamentals Need continued collaboration among stakeholders-- program developers, wind industry, power industry, other