Experience with Model Validation of PV Power Plants. Abraham Ellis, Ryan Elliott, Ray Byrne Sandia National Laboratories

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1 1 Experience with Model Validation of PV Power Plants Abraham Ellis, Ryan Elliott, Ray Byrne Sandia National Laboratories

2 2 Outline Overview: PV Plants and WECC/REMTF Models Status of WECC/REMTF generic model implementation Experience with model validation Summary remarks

3 PV Power Plants The amount of photovoltaic (PV) generation in the system is growing very rapidly. The size of PV plants is growing as well Some examples: Agua Caliente, AZ USA (290MWac), CVSR, CA USA (250 MWac), Longyangxia, Qinghai, China (320MW) Even larger PV plants (>500MW) are under construction With respect to plant topology and grid interface, PV Plants are similar to wind plants 250kW to 1 MW inverters MV AC collector system Substation, plant controls Power flow and dynamic representation is similar

4 WECC REMTF PV Plant Model The WECC/REMTF generic model for PV Power Plants uses three WECC/REMTF modules: REPC_A, REEC_B and REGC_A REEC_B model is a simplified version of REEC_A REEPC_A and REGC_A are identical to those used for wind Type 3/4 REMTF Module Usage REPC_A REEC_A, REEC_B REGC_A WTGT_A WTGAR_A WTGPT_A Wind/PV plant controller Wind /PV electrical controls Generator/Converter model Drive Train Aerodynamic model Pitch control PV Plants Type 4 WTG Plants Type 3 WTG Plants WTGTQ_A Torque control

5 5 WECC REMTF PV Plant Model Dynamic Model Topology REPC_A Vt REEC_B Vt REGC_A Vreg Vref Qr ef Qbranch Pr ef Pbranch Fr eq_ref Fr eg Plant Level V/ Q Cont rol Plant Level P Cont rol Qext Pr ef Q Cont rol P Cont rol Iqcmd Ipcmd Current Limit Logic Iqcmd Ipcmd Generat or Model Iq Ip Net work Solut ion Pqf lag Power flow assumptions Explicit representation of generator Equivalent (single-machine) collector system trip Protection Module Vt, f

6 6 Inverter P/Q Electrical Controls REEC_B basic features Power factor control and voltage dip response Active power limits and rate-of-change limit Current limits with P or Q priority

7 7 Model Implementation WECC/REMTF generic models for PV power plants are available in major commercial software platforms As with any other model, the user is responsible for providing model parameters Useful reference WECC PV Plant Dynamic Modeling Guideline

8 8 Model Validation Validated models are needed for system planning and interconnection studies In the US, entities such as NERC and WECC have model validation standards and guidelines Periodic validation is required for compliance Industry experience with plant-level validation of PV and wind plant models is relatively limited Efforts to develop validation guidelines and supporting tools (e.g., for generic model parameter identification) are on-going

9 9 Components of a Validation Tool 1) Dynamic models that correspond well to commercial tools 2) Simple equivalent impedance model to reflect PMU measurements to the terminal bus 3) Parameter fitting algorithm using norm minimization as an objective (must be balanced with engineering judgment)

10 10 Model Validation Guidelines WECC model validation policy addresses wind & solar: Wind and PV plant models must be validated against Reference Data Reference data can be plant-level measurements (e.g., PMU), type test (e.g., bench or field test of individual WTG or PV inverter), or manufacturer reference data (e.g., validated transient models) Validation must address active/reactive power capability, active/reactive power controls, protection for different output conditions (e.g, partial output and full output) Reference: WECC Generating Facility Data, Testing and Model Validation Requirements

11 11 Inverter-level Validation Example Bench test performed on a 3-phase, 50kW PV inverter in a laboratory environment Response to a symmetrical 75% voltage deviation In this example, the parameter fit was done manually (development of validation tool is ongoing)

12 Plant-level Validation Example This example is for a large PV plant (>100MW) A 12 MVAR 34.5 kv capacitor in the collector system was switched Data was useful to validate plant-level reactive control parameters Courtesy of Sachin Soni, Vladimir Chadliev, First Solar

13 13 Plant-level Validation Example PMU data from a 20 MW PV plant, approximately While not a perfect fit, it demonstrates the value of using PMU data for model validation This event is not ideal for model validation because of its long duration (>0.5 sec) Inverter s maximum power tracking (not modeled) results in slow active power recovery after fault clearing

14 14 Summary PV power plant representation is similar to wind power plant representation WECC/REMTF models are now available in major simulation software platforms User is responsible for providing parameters Model validation can be performed against bench tests, field disturbances, or staged tests The usual challenges apply: data quality, nature of event, Initial experience with generic model validation is positive

15 Open Discussion