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Wind Power Generation Power Flow and Dynamic Modeling Vadim Zheglov EnerNex, Tennessee [email protected] Eduard Muljadi NREL, Golden CO [email protected] UWIG-EnerNex Modeling Workshop Albany, NY July 5-6, 2011 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Background NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Conventional vs. Wind Power Plant Load Load Other Conv. Generator POI or PointPOI of or connection Interconnection to the grid Interconnection Interconnection Transmission Line Transmission Line GSU Xfmr Large Synchronous Generator Collector Collector System System Station Station Prime Mover Individual WTGs Individual WTGs Feeders and Laterals (overhead Feeders and Laterals (overhead and/or underground) and/or underground) NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Power Generation Conventional vs Wind Power Plant • Single or multiple large (100 MW) generators. • Many (hundreds) of wind turbines (1 MW – 5 MW each) • Prime mover: steam, combustion engine – non-renewable fuel affected by fuel cost, politics, and pollution restrictions. • Prime mover: wind (wind turbine) –renewable (free, natural, pollution free) • Controllability: adjustable up to max limit and down to min limit. • Controllability: curtailment • Predictability: preplanned generation based on load forecasting, influenced by human operation based on optimum operation (scheduled operation). • Predictability: wind variability based on wind forecasting, influenced more by nature (wind) than human, based on maximizing energy production (unscheduled operation). • Located relatively close to the load center. • Located at wind resource, it may be far from the load center. • Generator: synchronous generator • Generator: Four different types (fixed speed, variable slip, variable speed, full converter) – non synchronous generation • Fixed speed – no slip: flux is controlled via exciter winding. Flux and rotor rotate synchronously. • Type 3 & 4: variable speed with flux oriented controller (FOC) via power converter. Rotor does not have to rotate synchronously. NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Power Generation Types of Wind Turbine Generator Four basic topologies based on grid interface: – Type 1 – 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 1 Type 2 Type 3 Pla nt Fee ders Plant Feeders gene rator generator PF control capacitor s Slip power as heat loss Plant Feeders gene rator ac to dc PF control capacitor s Type 4 Plant Feeders generator ac to dc dc to ac ac to dc dc to ac full power partial power NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Power Flow Modeling Wind Turbine Generator NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC WPP Representation POI or connection to the grid Collector System Station Interconnection Transmission Line Individual WTGs Collector System Equivalent Feeders and Laterals (overhead and/or underground) Req Beq/2 jXeq Beq/2 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Equivalencing NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Equivalencing NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Pad-Mounted Transformer NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Reactive Compensations Represented by Separate Model Type 1 and 2 WTGs are induction machines: • Several stages of capacitors banks at the WTG terminals are normally applied . Net power factor at bus 5 ~ 1.0 • In power flow: • modeled as fixed shunt devices • WTG of type 1 is approximately PF=0.9 therefore the capacitor need is about to be ½ of the power output. • example, for a 100 MW WPP at full output, Qmin = Qmax = -50 Mvar • and add a 50 Mvar shunt capacitor at the WTG terminals. • Plant level reactive compensation may still be installed to meet interconnection requirements and should be explicitly represented in power flow. NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Reactive Compensations Type 3 and Type 4 WTGs (an estimate to start depending on the terminal voltage) • These WTGs are capable of adjusting power factor to a desired value within the rating of the generator and converter. They are also capable of voltage control at the interconnection point or at its terminals. • External reactive power compensation is often required to meet interconnection requirements • If these WTGs do not participate in voltage control, the equivalent generator should be assigned a fixed power factor, typically unity. (i.e., Qmin = Qmax = 0). • If the WTGs do participate in voltage control, then the equivalent generator should be assigned a reactive capability approximately equal to the aggregate WTG reactive power range (i.e., Qmin = Srated tan(cos-1(0.90); and Qmax = Srated tan(cos-1(0.95)) ). • For example, consider a 100 MW WPP that employs Type 4 WTGs with specified power factor range +/-0.95 at full output. In this example, Qmin should be set to -33 Mvar and Qmax should be set to +33 Mvar. At an output level below rated, the reactive limits should be adjusted according to the WTG capability curve. NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Reactive Power Flow I + jI X + jI X VB VA A A = B VA = VB QA =QB= 0.5 I2X A B B I jI X QB =I2X ; QA= 0 QA =I2X ; QB= 0 VA VA VA’ VA” VA= 1.0 I I I I VB = 1.0 V < V ; = 0 VB = 1.0 VA > VB ; B = 0 A B A - - All Q comes from B VA All Q comes from A VA jI X VB = 1.0 Equal Q (VAR) contribution I’ VB = 1.0 Overexcited I” VB”= 1.1 VA’ > VA ; QA =I’2X ; QB< 0 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Reactive Compensations POI or connection to the grid Turbine close to substation Collector System Station Interconnection Transmission Line Turbine far from substation Individual WTGs Feeders and Laterals (overhead and/or underground) X100 > X1 IX100 > IX1 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Practical Limit of Reactive Power Output • Due to collector system effects, some WTGs in the WPP will actually reach terminal voltage limits before reaching the nameplate reactive power limits. • The net effect is that actual reactive power capability could be less than the nameplate. • The reactive power capability can be determined by field test or careful observation of WPP performance during abnormally high or low system voltage. • For example, Figure 7 shows the results of field tests to determine the practical reactive limits of a 200 MW WPP. • All measurements were made at the interconnection point. Taking into account the effect of transformer and collector system impedances, the reactive power limits of the equivalent WTG can be established. • Currently, there are no industry standard guidelines for testing WPP steady-state reactive limits. NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Practical Limit of Reactive Power Output +95 and VPOI VA Vinf I reactor NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Practical Limit of Reactive Power Output VPOI VA Vinf I NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Validation Detailed Vs. Single-Machine Representations 0.435 QWT = 3-phase fault, all WTGs at 12 m/sec 0 -0.435 P34.5 kV Q34.5 kV From « Validation of the WECC Single-Machine Equivalent Power Plant », Presented DPWPG-WG Meeting at IEEE PSCE, March 2009 - Jacques Brochu, Richard Gagnon, Christian Larose, Hydro Quebec NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Validation Detailed Vs. Single-Machine Representations QWT = 0.435 3-phase fault, different wind speed for each feeder 0 -0.435 1 and 2 feeders P34.5 kV 4 feeders = Typical 2 and 4 feeders = Typical Q34.5 kV 1 feeder From « Validation of the WECC Single-Machine Equivalent Power Plant », Presented DPWPG-WG Meeting at IEEE PSCE, March 2009 - Jacques Brochu, Richard Gagnon, Christian Larose, Hydro Quebec NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Wind Power Plant Network 34.4/230 kV station transformer 230 kV Line 1 Infinite Bus R1, X1, B1 Rt, Xt. 0.6/34.4kV equivalent GSU transformer 34.5 kV collector system equivalent Re, Xe, Be Rte, Xte Gen Ideal Gen 4 1 230 kV Line 2 R2, X2, B2 2 3 Station‐level shunt compensation 5 Turbine‐level shunt compensation 100 MW equivalent wind turbine generator NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Power Flow Power Flow • Prepare the network (line branches, transformers, generators, and the loads). • Set the level of the loads and generations. • For wind turbine generator: • Type 1 and 2 – set the level of real power and reactive power, set the maximum and minimum limits of the real and reactive power. set the level of capacitor compensation. • Type 3 and 4 – set the level of real power and reactive power, and set the maximum and minimum limits of real and reactive power • Run the power flow program • Observe the abnormal operation (over load lines, over/under voltage buses and make adjustments as necessary. • Repeat the process for different scenarios: load change, generation change, line disconnected NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Power Flow Data NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Power Flow Assessment Pre‐fault Condition Fault Event 230 kV Line 1 Infinite Bus 34.4/230 kV station transformer R1, X1, B1 Rt, Xt. 0.6/34.4kV equivalent GSU transformer 34.5 kV collector system equivalent Re, Xe, Be Rte, Xte Ideal Gen Gen 4 1 230 kV Line 2 R2, X2, B2 2 Station‐level shunt compensation 34.4/230 kV station transformer 230 kV Line 1 Infinite Bus 3 R1, X1, B1 Rt, Xt. 100 MW equivalent wind turbine generator 5 Turbine‐level shunt compensation 0.6/34.4kV equivalent GSU transformer 34.5 kV collector system equivalent Re, Xe, Be Rte, Xte Ideal Gen Gen 4 1 230 kV Line 2 R2, X2, B2 2 3 Station‐level shunt compensation 5 100 MW equivalent wind turbine generator Turbine‐level shunt compensation Post‐fault Condition NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Power Flow Assessment Pre‐fault Condition Post‐fault Condition NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Modeling Wind Turbine Generator NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Modeling Needs G2 Dynamic models are needed to study the dynamic behavior of power system. Users include system planners and operators, generation developers, equipment manufacturers, researchers, and consultants. Wind Power Plant (WPP) models are needed to study the impact of proposed or existing wind power plants on power system and vice versa (i.e. to keep voltage and frequency within acceptable limits). Models need to reproduce WPP behavior during transient events such as faults/clear events, generation/load tripping, etc. G1 Short Circuit loss of line new line Resizing WTG wind turbine generator G3 NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Modeling Check List Check List: • Prepare the power flow model and run the power flow to ensure that the pre-fault and post-fault condition results are acceptable and makes sense. • For wind turbine generator: • Prepare the wind turbine dynamic model to be represented • If the wind turbine parameters (of the WECC generic models) are not available from the turbine manufacturers, use the default data provided by the generic models available from the WECC website • If the wind turbine parameters (of the WECC generic models) of the turbines to be simulated are available from the turbine manufacturers, use the latest model parameters provided. • Prepare the dynamic script of the scenario of interests and run the dynamic simulation for the contingencies fault, loss of lines, etc.) to be investigated. NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Modeling Time Scale Switching Transients Subsynchronous Resonance Transient Stability Oscillatory Stability Long-term Dynamics 10-6 10-5 10-4 .001 .01 .1 1 cycle Source: Dynamic Simulation Applications Using PSLF – Short Course Note – GE Energy 1 10 100 1 minute 1000 104 1 hour TIME (seconds) NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Models WECC Generic Models Generic model development in PSSE/PSLF – Complete suite of prototype models implemented PSLF PSSE Model Type Generator Excitation / Controller Turbine Pitch Controller Type 1 wt1g Type 2 wt2g wt2e wt2t wt2p Type 3 wt3g wt3e wt3t wt3p Type 4 wt4g wt4e wt4t wt4p Generic model Generator El. Controller Turbine/shaft Pitch control Pseudo Gov/: aerodynamics WT1 WT1G WT3 WT3G WT3E WT3T WT3P WT4 WT4G WT4E WT12T WT2 WT2G WT2E WT12T WT12A WT12A wt1t wt1p Current focus – Model validation & refinement (e.g., freq. response) – Identification of generic model parameters for different manufacturers (at NREL) NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Models WTG Type 1 and 2 Pla nt Fee ders Plant Feeders Type 1 WTG gene rator Type 2 WTG gene rator PF control capacitor s Slip power as heat loss ac to dc PF control capacitor s NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Models WTG Type 3 and 4 Plant Feeders Type 3 WTG Plant Feede rs Type 4 WTG generator ac to dc dc to ac genera tor ac to dc dc to ac full power partial power NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Single Turbine Representation Major components of WPP Equivalent Representation: • • • • Wind Turbine Generator (WTG) Equivalent and power factor correction (PFC) caps Plant level reactive power compensation if applicable Pad-mounted Transformer Equivalent Collector System Equivalent branch. Interconnection Transmission Line Station Transformer(s) Collector System Equivalent Pad-mounted Transformer Equivalent W POI or Connection to the Transmission System Plant-level Reactive Compensation Wind Turbine Generator Equivalent PF Correction Shunt Capacitors NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Multiple Turbine Representation In some cases, multiple turbine representation may be appropriate, for example: • To represent groups of turbines from different types or manufacturers • To represent a group of turbines connected to a long line within the wind plant • To represent a group turbines with different control algorithms. Collector System Equivalent #1 considered to be a long/weak line feeder Pad-mounted Transformer Equivalent #1 WTG Equivalent #1 of Type 3 Voltage controlled W Interconnection Transmission Line 21 MW Station Transformer(s) Collector System Equivalent #2 Pad-mounted Transformer Equivalent #2 34 MW W POI or Connection to the Transmission System WTG Equivalent #2 Type 1 PF Correction Shunt Capacitors Pad-mounted Transformer Equivalent #3 Total Output 100 MW WTG Equivalent #3 of Type 3 PF=1 W Collector System Equivalent #3 45 MW NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Model Validation •Prepare the simulation carefully (i.e. the correct information must be used): type of WTG, collector system impedance, transformers, power system network, input parameters to dynamic models, control flags settings set-up, reactive power compensation at the turbine level or at the plant level. •Initialize the simulation based on pre-fault condition (check v, i, p, q, f, if available). •Recreate the nature of the faults if possible, otherwise use the recorded data to drive the simulation and compare the measured output to the simulated output (pre-fault, during the fault, post-fault). •Represent the events for the duration of observation (any changes in wind, how many turbine were taken offline due to the fault?). •Prepare the data measured to match the designed frequency range of the software used. •Field data is expensive to monitor, public domain data is limited, difficult to get, and quality of data needs to be scrutinized – – Anticipate errors in the measurement and make the necessary correction The location of simulation should be measured at the corresponding monitored data. NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Model Validation Example Example of Dynamic Model Simulation versus Field Data (Type 3) Interconnection Transmission Line Station Transformer(s) Collector System Equivalent POI or Connection to the Transmission System Two Turbine Representation Pad-mounted Transformer Equivalent W 91% WTGs stays “on” after the fault. W 9% WTGs were dropped of line during the fault. Complete Representation (136 turbines) Interconnection Transmission Line Station Transformer(s) 136 WTGs were represented POI or Connection to the Transmission System 9% WTGs were dropped of line during the fault. NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Model Validation Example Real Power Comparison V and f 1.2 140 1.15 Q-sim-1wtg (MVAR) Q-measured (MVAR) Q-sim-136WTG 60 1.07 0.6 1.03 0.4 100 R e a l P o w e r (M W ) 0.8 R e a c tiv e P o w e r (M V A R ) 1.11 F re q u e n c y (p .u .) V o lta g e (p .u .) 80 P-sim-1wtg (MW) P-measured (MW) P-sim-136WTG 120 1 Reactive Power Comparison 80 60 40 40 20 0 0 0.5 1 1.5 2 2.5 3 -20 0.99 20 V f 0.2 0 0.95 0 0.5 1 1.5 -40 -60 0 2 0.5 1 1.5 2 2.5 3 3.5 4 Time (s) Time (s) Time (s) Compare P&Q measured to P&Q simulated V and f System Generator A C B W Input V and f Wind Turbine Generator Equivalent Regulated Bus NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC 3.5 4 Dynamic Model Validation Comparison against other model (Benchmarking) •Another method to validate new model is to use another model that has been validated against field measurement as a benchmark model. •Several transient fault scenarios can be performed using both models, and the results can be compared. •Parameter Tuning – The new model and the benchmark model may have some differences in implementation, we may have to perform parameter tuning to match the output of the benchmark model. – However, one should realize that the model may not be able to match the output of the benchmark model in all transient events. •Parameter Sensitivity – In order to limit the number of parameters that should be tuned, parameter sensitivity analysis may need to be performed. – In general important parameters are varied one by one and the sensitive parameters can be tuned to match the bench mark model. NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Dynamic Model Validation Example Example of Model to Model Comparison (Type 2 “Detailed” Model vs Generic Model) Terminal Voltage Reactive Power Real Power Turbine Speed NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC